75W 140 Gear Oil in Final Drive

[fatbob]

Riders:

In the latest edition of the MOA magazine, service guru Paul Glaves suggests that using the synthetic 75W 140 Gear Oil in an R bike with a ball bearing final drive is contributing to failures of same. What say you, anyone heard of any connection of this oil to failures?

 

Bob

[ShovelStrokeEd]

Nothing specific but, too heavy a lubricant in a ball bearing is not a good idea. The balls need to float on a thin film of this lubricant to keep from making metal to metal contact with the races. Problem is, they also need to turn to distribute the load over series of surfaces spread out over time. Too thick and they will be reluctant to turn, in fact, the wedging action of the lubricant at the area near the almost contact point can bring the ball to a halt. Add an impact load and you have a bad bearing. Might not fail now but life will be reduced.

 

The final drive bearing is already heavily loaded and doesn't really turn at very high RPM. Other than gear friction, there is very little heat generated in the final drive so a multi-viscocity oil doesn't make sense.

[Stan Walker]

there is very little heat generated in the final drive

 

So running cold means that the oil is the same weight as a 75W single grade GL5 oil. That's close enough to 90W to not make a whole lot of difference in my opinion. Plus the final drive doesn't run at ambient, maybe at ambient plus 40 degrees?

 

While not setting any records here for mileage, I do have two RT's (160,000 miles combined) and both have run on 75W140 in both the tranny and final drives for almost their entire life. No final drive or tranny bearing failures in either bike.

 

While I like Paul, and respect his mechanical ability, this is a case where he presented a conclusion with no supporting evidence to back it up. Or maybe the editors stripped that from the article.

 

Perhaps what is needed here is for someone to put together a poll and see if there is a pattern to the oil weight used in final drives that have had big bearing failures.

 

I do agree their is no need for 75W140 in the final drive. But it is convenient since I already have it out.

 

Stan

[Ken H.]

Until they moved to Texas last year the Glaves lived about 20 miles from us and I listened to him talk to this subject at one of his tech days. His basic point is people are playing with all kinds of different lubes in the transmissions and final drives of BMW motorcycles, largely fueled by anecdotal testimonials on the Internet (like here for example), then wondering why they are having failures. And blaming BMW for them to boot. His point - on this at least, stick with the manufacturer's recommendations.

[T__]

Riders:

In the latest edition of the MOA magazine, service guru Paul Glaves suggests that using the synthetic 75W 140 Gear Oil in an R bike with a ball bearing final drive is contributing to failures of same. What say you, anyone heard of any connection of this oil to failures?

 

Bob

 

 

Bob, what reason does Mr. Glaves give for his reasoning?..

 

Personally I have some reservations down those same lines but my thoughts are based more on the additive content of the Synthetic based gear oils than their Viscosity or Synthetic structure.. Basically the Synthetic based newer gear oil’s are blended for low friction (for fuel economy) & severe wear protection of the ring & pinion (neither of which is really a problem with the BMW final drive.. Tight dimension ball bearings don’t always adequately handle additive build up from certain molybdenum based gear oil additive packages..

 

Personally, I am a big fan of PREMIMUM synthetic motor oil but still use conventional gear oil in the final drive.. On the other hand I do use up-level Synthetic gear oil in my trailer pulling truck’s diff as I need the gear tooth heat protection there..

 

Twisty

[smiller]

service guru Paul Glaves suggests that using the synthetic 75W 140 Gear Oil in an R bike with a ball bearing final drive is contributing to failures of same.

Without testing and analysis any such statement is nothing but conjecture, as are any recommendations to stray from the OEM recommended lube.

 

From the data we've collected thus far on final frive failures (and to the extent it is accurate and representative) there is a very clear cluster of failures based on production date, and this would seem to clearly indicate an assembly issue. My personal guess is that if the rear drive was set up properly from the factory it more often than not will have a long life regardless of what weight oil you have in there, and if it was set up poorly it will likely have a short life, regardless of what weight oil you have in there.

 

Bottom line, stick with BMW's recommendation and cross your fingers (especially if you have a '99.)

[big-t]

 

I remember reading an interview with someone from the company that built the final drives for the 1100's.I believe they highly recommended using only the oil weight specified,and using an oil of a different weight could cause failure.

 

..course all mfgs say that.

 

I'll see if I can find that interview when I get home.

[Yeeha! Stephen]

My '02 had a Final Drive failure at 50k. It had, up to that time, always been serviced with BMW oils/lubes at the correct weights.

 

After that failure I went with Bel Ray 85w140 in the Tranny and Final Drive. Now at 90k, no signs of problems yet.

 

Reading the story in MOA, I'm second guessing myself and have the urge to go to 90w. 40k miles on 85/140, it's probably too late to switch back to 90w and save myself from the problems of bearing/race failure... but I still have the urge. Hmmmmm...

 

One thing I do now though. I change Tranny and Final Drive oil at every service. Not so much as to have fresh oil, as to check the Final Drive fluid for metal flakes and shavings.

 

Oil is cheap compared to $$ for a Final Drive.

 

And... should I make that run to Cycle Gear this morning and pick up some 90w?

[philbytx]

Stephen,

If it's on your mind....go do the 75w90 thing!

Second guessing yourself sucks mate- AMHIK

 

FYI - I run 75w140 synth. in the gearbox and 75w90 Mobil1 in the rear .

[DavidEBSmith]

stick with the manufacturer's recommendations.

 

That's one of the problems. Various BMW owner's and service manuals say different things. It's not clear whether 75W140 was available when the early manuals were published, so we don't know if they don't list it because it didn't exist or because it's not good for those models. BMW sells this 75W140 stuff labeled "Recommended for all BMW motorcycles after 1970." Some dealers recommend it and some don't. You would think that BMW wouldn't sell oil that's bad for their final drives, but . . .

[Yeeha! Stephen]

Stephen,

If it's on your mind....go do the 75w90 thing!

Second guessing yourself sucks mate- AMHIK

 

FYI - I run 75w140 synth. in the gearbox and 75w90 Mobil1 in the rear .

 

Ha! I ran down to Cycle Gear (just a few blocks away from my house) and bought some Bel Ray 90w gear oil.

 

Funny thing is, it's too hot to go out into the garage and change it now. I'll have to wait till this eveing when it cools off. Soooo... I sit here staring at the bottle and continue to wonder. Should I, or shouldn't I? Jeez, it's another 9 hours till dark and the garage starts to cool off.

 

[breyfogle]

So running cold means that the oil is the same weight as a 75W single grade GL5 oil. That's close enough to 90W to not make a whole lot of difference in my opinion.

IIRC, The "W" rating is measured at 32 degF and the "hot" rating is measured at 212 degF. I would agree that the difference between 75W and 90W is minimal *IF* the ambient temp was near freezing but the difference is much greater at typical operating temps.

[Ralph]

Funny thing, I changed from the BMW 75-140 to Mobil 75-140 just before a trip & found the tranny harder to shift with the Mobil gear oill. ?????

[Stan Walker]

but the difference is much greater at typical operating temps.

 

 

Assuming that the slope of the multi-grade is linear.

 

The point where the 75W140 is the same as a 90W oil is 73.5 degrees. Perfect riding weather....

 

Stan

[E30TECH]

 

Ha! I ran down to Cycle Gear (just a few blocks away from my house) and bought some Bel Ray 90w gear oil.

 

Please tell me you aren't serious about using Bel Ray

[T__]

So running cold means that the oil is the same weight as a 75W single grade GL5 oil. That's close enough to 90W to not make a whole lot of difference in my opinion.

IIRC, The "W" rating is measured at 32 degF and the "hot" rating is measured at 212 degF. I would agree that the difference between 75W and 90W is minimal *IF* the ambient temp was near freezing but the difference is much greater at typical operating temps.

 

Breyfogle, first off gear oil is not W rated at 32°c (never was) ,, the low flow rating is not used much in gear oil anymore (since about mid 2005) instead the low number (a basic low temp flow rating) is now usually specified as the temperature at which the oil flows at 150,000cP viscosity.. If you were to test for the low number flowability it would be done at 40°c (about 104°f).. This is according to the most commonly used gear oil spec SAE J306.. That is even different now than it was before mid 2005 so if your motorcycle speced a specific gear oil grade prior to mid 2005 it could be a different spec now (there was so great of a spread in the early (pre 2005) SAE J306 spec that there was no way for a manufacturer to be sure the proper viscosity gear oil would be used at replacement.. The new revised (mid 2005 & up) SAE J306 spec tightened up the 100°c viscosity spec in the 90weight & up ranges.. Gear oil specification is not nearly as cut & dried as the motor oil rating spec.. The good news is the vast variation in pre 2005 gear oil specs mostly effected fuel economy & not hot performance..

 

Twisty

[breyfogle]

I was not aware that gear oil was spec'd different from motor oil, its never too late to learn something.

[wolcott]

Right before I was due to change my trans fluid and final drive fluid, I was down at the local BMW shop looking at some motorcycle clothing. When the mechanic (who installed my front master cylinder) walked by, I stopped him and asked him if I should run synthetic or regular 75W-90 in the final drive. He said to run regular old dino 75W-90; so on his advice I am running Valvoline dino 75W-90. This is the only non-synthetic I am running; the motor is running Mobil 1 15W-50 ext. performance oil, and the tranny has Redline Heavy Shockproof gear oil in it. I wondered at the time why this mechanic preferred dino in the final drive.

[Yeeha! Stephen]

 

Ha! I ran down to Cycle Gear (just a few blocks away from my house) and bought some Bel Ray 90w gear oil.

 

Please tell me you aren't serious about using Bel Ray

 

 

OK, I'll bite... what do you think is wrong with Bel Ray oils?

 

 

I've never had any problems with them. Many bikes on my list have run it. It's surely done better than the factory oil that I stuck with and let me down. (no proof, my final drive failure may well have been setup problems)

[11101110]

I recently saw a viscotity comparison between engine oil scale and gear oil scale. The numbers are not equal. Meaning that 40W engine oil can actually compare, on viscotity alone, with say 75W gear oil. Or take an engine and gear oil of same weight and the gear oil will have a lower viscosity.

 

Additionally I was reading about bearing lubrication in an industry mag (I think). It said most bearing manufactures are against using multiweight oil to lube their bearings.

[E30TECH]

 

 

OK, I'll bite... what do you think is wrong with Bel Ray oils?

 

Nothing that I know of, just messing with you

[T__]

I recently saw a viscotity comparison between engine oil scale and gear oil scale. The numbers are not equal. Meaning that 40W engine oil can actually compare, on viscotity alone, with say 75W gear oil. Or take an engine and gear oil of same weight and the gear oil will have a lower viscosity.

 

Additionally I was reading about bearing lubrication in an industry mag (I think). It said most bearing manufactures are against using multiweight oil to lube their bearings.

 

Damon, the direct comparison between SAE rated motor oil & SAE rated gear oil is quite difficult,, as you have mentioned the rating scale is different.. Plus there is a lot of overlap due to the large viscosity range of gear oil.. I have an older comparison chart so don’t know how current these viscosity overlaps are (use this for comparison only) but lets start with 75 weight rated gear oil-

 

--75 weight gear oil pretty well encompasses the entire spectrum of 10 & 15 weight motor oil & the bottom of the 20 weight motor oil viscosity range..

 

-- 80 weight gear oil encompasses the top of the 20 weight motor oil & most of the 30 weight motor oil viscosity range ..

 

--85 weight gear oil encompasses the top of the 30 weight & bottom of the 40 weight motor oil (that (85W) is the newer rating so the 85 weight gear oil band is narrower than either of the old 80 or 90 weight bands..

 

--90 weight gear oil is a broad older spectrum so that encompasses the top of the 40 weight motor oil,, all of the 50 weight motor oil,, & about all of the 60 weight motor oil viscosity range..

 

As a general rule a good quality 20W50 motor oil will meet 75w,80w, & 90w GL-1 gear oil specs.. In fact for some types of non GL-5 usage, motor oil is superior to gear oil in it’s additives & antifoaming qualities.. There are a lot of manual transmissions that spec out 5w30 or 10w40 motor oil as the preferred lubricant.. Where motor oil falls short is in the GL-5 area as there is little to no E.P. (extreme pressure) additives in motor oil.. Anything with a Hypoid type gear set should not use a GL-1 lube or motor oil type lubricant as the gear tooth loads need a GL-5 type EP gear oil to survive under heavy load..

 

Twisty

[E30TECH]

Does the BMW 75w140 super synthetic have a GL5 rating?

[philbytx]

Yuppers!

[oldhway]

Man I find oil threads riveting , so here's my .02 worth; I just did the full lube thing on the'04 RT. Mobil 1 15w-50 gold cap in the motor, Mobil 1 75w-90 gear oil in the tranny, Spectro hypoid GL5 in the final drive. I had been running the heavier gear oil from Mobil 1 in the tranny and the shifting is muuuch easier now. Who knew? Final drive is flake free but came out awfully thick. Used the heavier Mobil 1 last time and definitely won't again. Change all oils at every oil change; Overkill? perhaps but it makes me happy. We all have to waste our money somehow. The comb. of oils I have in now is where I'll stay since the beast seems very happy with this set-up.

 

Again, just my equally riveting contribution. Now if you want to talk about tires.....

[E30TECH]

Yuppers!

 

I got my 2 bottles from the Ebay auction you posted. I didn't see anything on the bottle stating GL-5. Figured I'd ask.

[R1100RSpurist]

really! i still havent gotten mine...and he has not responded to my inquiries.

[E30TECH]

He sent it via UPS. I just got it yesterday. I'd give it a few more days...

[Yeeha! Stephen]

 

 

OK, I'll bite... what do you think is wrong with Bel Ray oils?

 

Nothing that I know of, just messing with you

 

 

Hook, Line, and Sinker...

 

 

I was hoping nothing bad about Bel Ray Dino Oil would come out. As often as I change the gear lubes, Synth is just a waste of $$ for me.

[philbytx]

Just got mine today via OOPS

[keithb]

OK. Enough of your gloating over your $8 tranny oil. I had to pay $17 for a quart of Mobil 1 75W140 yesterday. Just kidding. Enjoy your deal but just let me in on it next time.

[Bill_Walker]

I just read the article, and checked my owner's manual, which indeed only calls for SAE 90 GL5 for the trans and rear end. Why, then, does BMW sell BMW-labeled 75W-140 synthetic gear lube? For the sake of convenience and completeness, I've blown my money on the tune-up kits sold by Sierra BMW. The 12,000 mile kits include the 75W-140 synthetic. My trans shifts a heck of a lot better with the BMW 75W-140 synthetic, but I can't speak to its longevity, with only 30,000 miles on my bike.

[T__]

I just read the article, and checked my owner's manual, which indeed only calls for SAE 90 GL5 for the trans and rear end. Why, then, does BMW sell BMW-labeled 75W-140 synthetic gear lube? For the sake of convenience and completeness, I've blown my money on the tune-up kits sold by Sierra BMW. The 12,000 mile kits include the 75W-140 synthetic. My trans shifts a heck of a lot better with the BMW 75W-140 synthetic, but I can't speak to its longevity, with only 30,000 miles on my bike.

 

Bill, because the 75W-140 synthetic easily meets or exceeds the VERY BROAD 90 weight gear oil requirement.. As a rule gear oil (trans or final drive) is speced out for proper viscosity at normal to maximum operating temperatures.. Because the pre 2005 90 weight gear oil spec was so broad just about all of the modern multi-weights in the 75-140 range will fall within the guidelines.. But, just because it meets the OEM BMW spec doesn’t make it better or even as good..

 

I think you will find the same thing in motor oil’s.. Seeing as motor oil is required to be backwards compatible the modern SL & SM motor oil’s easily meet the early BMW specs but as we all know MOST isn’t as good as the older “pre energy oil” as far as certain engine protection issues go..

 

The big question here is: HAS BMW FULLY DURABILITY tested that 75W140 in the older bikes or have they (their engineering staff) just looked at the specs & said arbitrarily that it is good to use as it seems to meet the original requirements?. Having been in that situation a number of times myself we (the engineering team) usually get it right based on engineering background & experience but every now & then we do get bit.. I’m old school when it comes to making engineering assumptions & am always in favor of the full hands on testing route but in a lot of cases the engineering team is overruled by outside influence like money or need to move on to a more important projects..

 

Twisty

[E30TECH]

OK. Enough of your gloating over your $8 tranny oil. I had to pay $17 for a quart of Mobil 1 75W140 yesterday. Just kidding. Enjoy your deal but just let me in on it next time.

 

It was $5 a qt (not $8)

[Spyder]

 

It was $5 a qt (not $8)

 

I'll give you $6 for it.

[philbytx]

Hey!

I DID post it on the board....first come, first served

[smiller]

OK. Enough of your gloating over your $8 tranny oil. I had to pay $17 for a quart of Mobil 1 75W140 yesterday. Just kidding. Enjoy your deal but just let me in on it next time.

Or you can all just buy Rotella 80W-90 for $3.85/qt. and in all likelihood not experience even the slightest difference in service life of the gearbox.

[keithb]

ARGH. I did not about the Rotella. Now I really feel silly. And Philby you guys scarfed up the oil before I could get there. I know, I know, first come, first served.

[E30TECH]

OK. Enough of your gloating over your $8 tranny oil. I had to pay $17 for a quart of Mobil 1 75W140 yesterday. Just kidding. Enjoy your deal but just let me in on it next time.

Or you can all just buy Rotella 80W-90 for $3.85/qt. and in all likelihood not experience even the slightest difference in service life of the gearbox.

 

That still leaves some doubt in my mind.....

 

I'll sell mine for $9/qt plus shipping. That 1/2 price folks. But I'm going to use this in the trans - so I'll use the rotella in the rear

[Bill_Walker]

Bill, because the 75W-140 synthetic easily meets or exceeds the VERY BROAD 90 weight gear oil requirement..

 

Thanks for explanation.

 

I’m old school when it comes to making engineering assumptions & am always in favor of the full hands on testing route but in a lot of cases the engineering team is overruled by outside influence like money or need to move on to a more important projects..

 

Twisty

 

"Sooner or later you have to shoot the engineers and ship the product" is the phrase the business types use, I believe.

 

I'm an engineer (electrical/software), too.

[Tipover_Bob]

Bob: Check out this article and then decide what weight oil you want to use in your final drive:

http://www.mrcbearingservices.com/docs/lubrication.pdf

 

Tipover Bob

[moshe_levy]

The level of confusion surrounding this issue is astounding. I asked the same question when I joined a year ago. I had the factory manual telling me to use 80W/90. I had a fluid (BMW's 75W/140) which according to the dealer was introduced after the printing date of my manual - so perhaps the manual is outdated in its recommendation. I have my local dealer putting Shell synth 85W/140 in all FD fluid changes, on some bikes which I've personally seen with over 100k on the original final drives.

 

it makes you wonder who is right, and what BMW has to gain by not being a little more specific in its labeling. The 75W/140 simply says "gear oil" and does not specify use in the tranny or FD, from what I recall.

 

FWIW, I've used both 80W/90 and then 75W/140. Next change, I'm going to just go back to 80W/90. Why? Because without objective evidence, I've got to trust the manual. And, if 75W/140 has no advantage over 80W/90 in the FD application specifically, why pay $17 per quart for it when 80W/90 synth is available for $6?

 

-MKL

[Tipover_Bob]

The level of confusion surrounding this issue is astounding. I asked the same question when I joined a year ago. I had the factory manual telling me to use 80W/90. I had a fluid (BMW's 75W/140) which according to the dealer was introduced after the printing date of my manual - so perhaps the manual is outdated in its recommendation. I have my local dealer putting Shell synth 85W/140 in all FD fluid changes, on some bikes which I've personally seen with over 100k on the original final drives.

 

it makes you wonder who is right, and what BMW has to gain by not being a little more specific in its labeling. The 75W/140 simply says "gear oil" and does not specify use in the tranny or FD, from what I recall.

 

FWIW, I've used both 80W/90 and then 75W/140. Next change, I'm going to just go back to 80W/90. Why? Because without objective evidence, I've got to trust the manual. And, if 75W/140 has no advantage over 80W/90 in the FD application specifically, why pay $17 per quart for it when 80W/90 synth is available for $6?

 

-MKL

 

MKL: If I told you that I had a wonderful 80W/5000 shockproof synthetic gear oil for your precious bearings and you knew that your bearings were specifically designed be lubricated by 90W oil, would you use it?

 

If that same situation was changed to a condition where you were putting extreme shock loads on gear teeth and weren't worried about bearings would you use it?

 

So, where do most of the problems lie in BMW transmissions and final drives? Personally, I am more aware of bearing failures than gear failures.

 

Tipover Bob

[T__]

The level of confusion surrounding this issue is astounding. I asked the same question when I joined a year ago. I had the factory manual telling me to use 80W/90. I had a fluid (BMW's 75W/140) which according to the dealer was introduced after the printing date of my manual - so perhaps the manual is outdated in its recommendation. I have my local dealer putting Shell synth 85W/140 in all FD fluid changes, on some bikes which I've personally seen with over 100k on the original final drives.

 

it makes you wonder who is right, and what BMW has to gain by not being a little more specific in its labeling. The 75W/140 simply says "gear oil" and does not specify use in the tranny or FD, from what I recall.

 

FWIW, I've used both 80W/90 and then 75W/140. Next change, I'm going to just go back to 80W/90. Why? Because without objective evidence, I've got to trust the manual. And, if 75W/140 has no advantage over 80W/90 in the FD application specifically, why pay $17 per quart for it when 80W/90 synth is available for $6?

 

-MKL

 

Moshe, using 75W140 in the final drive is like using 20W50 in the engine. In the mean operating temperature range they are probably about the same working viscosity.. The 75W140 has an advantage if you are trailer towing at 90 mph through death valley. It also has an advantage if you regularly ride off at 10° below 0.. Other than that you really don’t gain much unless the 75W140 has superior additives that YOU NEED for you riding style.. Keep in mind that when your manual was printed the 90 weight gear oil viscosity range was very broad so the 75W140 of late will fit into the old 90 weight spec range quite nicely.. (be a little thinner at below 0 & won’t thin out as much at 250°f but all practical purposes it will have close to the same viscosity at warm riding conditions.. Is the 75W140 worth the extra money (who knows,, maybe if the additive package Is better & you don’t EVER change your final drive oil).. The new never change final drive BMW’s spec out the synthetic stuff for a reason..

 

Twisty

[moshe_levy]

Like some others have mentioned is their practice, I too swap out all the fluids at 6k. I'm down there anyway, the fluid is cheap, and it gives me a chance to inspect the FT drain to see if there are any tell-tale particles floating about. I commute all year round, but rarely does the temp here fluctuate much outside the range of 10-100, so me thinks I won't see any real advantage to the 75W/140 anyhow.

 

-MKL

[Tipover_Bob]

Like some others have mentioned is their practice, I too swap out all the fluids at 6k. I'm down there anyway, the fluid is cheap, and it gives me a chance to inspect the FT drain to see if there are any tell-tale particles floating about. I commute all year round, but rarely does the temp here fluctuate much outside the range of 10-100, so me thinks I won't see any real advantage to the 75W/140 anyhow.

 

-MKL

 

MKL: From "Interview with Getrag":

 

SCHAETZLE: Oil should be seen as an integral part of the transmission. When designing the transmission the load bearing capability of the oil is part of the calculation. We fill the BMW transmissions with SAE 90 GL 5 gear oil manufactured by Fuchs, a brand mainly found as an OEM supplier.

 

SOMMER: SAE 90-Oil should be used throughout the whole year. It is true that in winter the shifting will suffer at first from the thick oil, but it should improve during a very short ride. For those to whom this is disturbing, because they make many short trips, for example, can use 75w90 GL 5 in winter as an alternative. In summer it must be changed back to SAE 90 GL 5.

 

Hope this is helpful.

 

Tipover Bob

[moshe_levy]

Bob-

 

Helpful, yes. Where's this from?

 

-MKL

[DavidEBSmith]

It's here, it's from a 1996 magazine article, and it's talking about oil technology 10 years ago. Again, we don't even know if there was a 75W140 when the article was written.

[philbytx]

At the end of the day...there is no right and wrong concerning BMW 75w40 IN THE TRANSMISSION. If you include the final drive in the "transmission" well, that's good for you. 75w90 is fine in both gearbox and final drive. HOWEVER, BMW now has an optional 75w140 gear oil that is available. And that availability is for whomever feels the need for 75w140 in their TRANNY.

 

Personally, I now live in Texas and do ride in HOT weather and 75w140 appeared ideal for this application. And frrom personal experience, I can honestly say that my gearshifts are way smoother with 75w140 than they were with 75w90....

Take that for what it's worth.

[Tipover_Bob]

At the end of the day...there is no right and wrong concerning BMW 75w40 IN THE TRANSMISSION. If you include the final drive in the "transmission" well, that's good for you. 75w90 is fine in both gearbox and final drive. HOWEVER, BMW now has an optional 75w140 gear oil that is available. And that availability is for whomever feels the need for 75w140 in their TRANNY.

 

Personally, I now live in Texas and do ride in HOT weather and 75w140 appeared ideal for this application. And frrom personal experience, I can honestly say that my gearshifts are way smoother with 75w140 than they were with 75w90....

Take that for what it's worth.

 

Phil: Thanks for responding to me.

 

A straight 90w gear oil is slightly thinner than a 140w and slightly thicker than an 85w. I ran a 90w LE 607 oil in my K75C transmission last year, and it did shift much smoother than the 85w 90. I had an old timer tell me that if the oil is too thick, it will just roll up and not provide proper lubrication. Also, in my opinion, if the oil is too thick, then it may impede the rotation of the bearings and cause extra scuffing. Also, if the oil is too thick, once the anti foaming additives wear out, it may allow extra heat to remain in the bearings because of decreased flow. Not only does the oil have to allow all the bearings to rotate, and lubricate between the metal parts, it must also carry heat away. If you don't have the correct viscosity, you can have a propensity to have failure from heat or scuffing.

 

I am just a tourer at heart. I don't like running my vehicles hard. For me, cooler running and reliability are what's important. If I was a hot dog (squid), I would definitely be more interested in the 140w shock proof because I would be slamming those gears.

 

Tipover Bob