Rear drive lube confusion

[RealWing]

I've been somehwhat confused about rear drive lube since I got my LT in May. This is what I've seen so far:
1. The 2006 Maintenance CD specifies Castrol MTX 75W140 – which is a full synthetic oil.

2. However, further down on the same page it specifies SAE 90 API GL5

3. My small Maintenance Manual specifies 90 weight GL5.

4. The 1999-2003 CDROM specified straight SAE 90 GL5.

5. My dealer supplied me with 80W90 mineral.

6. Both my dealer and some others on this forum state that BMW does not recommend synthetic oil in the rear drive because it does not stick very well when the bike sits for a long time. No one has seen any document that states this that I've heard of. Apparently the technicians have been told this at BMW training seminars.

7. My dealer also stated: "at service school where our techs go to get their training, the instructors advise our technicians to use the 80W90 Mineral oil."

Given all of that, I asked my dealer for something official from BMW and if I can use 75W140 as stated in my CDROM.

This is his reply: "BMW AG advocates the use of SAE 90 mineral oil OR if using synthetic they specify the Castrol MTX 75W140."

Looks like I've got the green light to run 75W140 synthetic - which I'm going to do (probably Amsoil "Severe Gear" lube).

After the change, I'll run some more oil anlaysis samples to see if there is any difference in wear rates etc.

[Florian]

I use the 80W90 in the rear. No issues.


F

[McAllister]

At my 60,000 check the mechanic said I should try non-synthetic oil in the rear drive for the same reasons you mentioned. He said the prevailing thought now was that the synthetic oil doesn't adhere to the gears as well as the regular oil and in that application the regular non-synthetic oil did a better job of lubricating the gear train. I'm guessing this is coming from the BMW training sessions. Anyone know for sure what the source is?

[tmgs]

At my 60,000 check the mechanic said I should try non-synthetic oil in the rear drive for the same reasons you mentioned. He said the prevailing thought now was that the synthetic oil doesn't adhere to the gears as well as the regular oil and in that application the regular non-synthetic oil did a better job of lubricating the gear train. I'm guessing this is coming from the BMW training sessions. Anyone know for sure what the source is?

it makes sense though, i have had one rear drive fail (at 52k I think) in 125k miles on my '02 I have alway's run Dino GL5 no syn in my final frive, I change it at every oil change 6k miles (in fact in the begining i was changing it every 3kish with the oil changes at 3k till i went to syn engine oil), just to kleep a eye out for abnormal wear.

Tom

[tmgs]

it makes sense though, i have had one rear drive fail (at 52k I think) in 125k miles on my '02 I have alway's run Dino GL5 no syn in my final frive, I change it at every oil change 6k miles (in fact in the begining i was changing it every 3kish with the oil changes at 3k till i went to syn engine oil), just to kleep a eye out for abnormal wear.

Tom
BTW the wifes RT has never had a final go, it as well has always had the rear drive lube changed at every oil change, I know of a few rt's that have had the final go.

[fredthead]

My dealer puts synthetic in the trans and rear drive. I guess he went to a different school?

[lnowell]

Red Line HD shockproof seems to stick to everything - including its plastic container. I have read that one of the problems (if it is a problem) is that synthetic is too slippery and may allow bearing to slide rather than roll as they were designed to do. If synthetic is ok in the engine, why is it not ok in the rear drive?

[wolfstudios]

I have used Mobil synthetic gear lube for 100,000 miles on my 99 LT and replaced every 3k miles.
I have also pulled a trailer for about 70,000 miles of those miles.
Since the LT was not desighned to pull a trailer, I had to change out the reardrive because of the too-much-backlash in the drive. I am not sure if it was the bearings or the meshed gears that produced the sloppiness. I still need to dismantle the drive and check when the time permits.

Is there anyone else that pulls a trailer with any comments?

Wondering,
George

[amsoilguy]

Hold on guys, don't assume anything from what a couple of BMW techs tell you . Technicians are just like any other paid employees, there are good ones and there are bad ones. BMW uses Castrol because Castrol won the contract for their business. BMW now has a vested interest to push Castrol products. Thats the issues plain and simple. As far as gear lube goes, use what the owners manual says to use as far as the API rating (GL-5) Brand name does not matter. BMW buy law, can not tell you what brand to use. THEY CAN ONLY SPECIFY API RATING. GL-5. What ever the dealer tells you verbally does not count. It states in your owners manual(or technical service bulletin) paper work that the written manual supersedes any verbal statement made by any BMW dealership or representative. Whats in writing is what counts.
Most cars today come from the factory with synthetic gear oil. I don't think BMW has the skinny on using dino oil in the Diff. The gears are partially submerged in the oil at stop and the moment the gears start to spin the unit is fully lubricated. This is not a motor start up issue. Synthetic oils are must better at preventing rust than conventional oils because of the coating that is present on the metal. So the idea that the oil does not stick to the metal is hogwash told by uninformed service techs.

[tmgs]

Hold on guys, don't assume anything from what a couple of BMW techs tell you . Technicians are just like any other paid employees, there are good ones and there are bad ones. BMW uses Castrol because Castrol won the contract for their business. BMW now has a vested interest to push Castrol products. Thats the issues plain and simple. As far as gear lube goes, use what the owners manual says to use as far as the API rating (GL-5) Brand name does not matter. BMW buy law, can not tell you what brand to use. THEY CAN ONLY SPECIFY API RATING. GL-5. What ever the dealer tells you verbally does not count. It states in your owners manual(or technical service bulletin) paper work that the written manual supersedes any verbal statement made by any BMW dealership or representative. Whats in writing is what counts.
Most cars today come from the factory with synthetic gear oil. I don't think BMW has the skinny on using dino oil in the Diff. The gears are partially submerged in the oil at stop and the moment the gears start to spin the unit is fully lubricated. This is not a motor start up issue. Synthetic oils are must better at preventing rust than conventional oils because of the coating that is present on the metal. So the idea that the oil does not stick to the metal is hogwash told by uninformed service techs.


OMG you don't sell snakeoil do you OH I MEAN amsoil, the number two oil ?
<g>

hehehehehehe sorry but I have to agree plain ol dino gear oil sticks to everything like glue. had to many diffs apart over the last 30 years being a tech, I'm just not sold on syn anything for everyday use. we will see how it works in thebeemer

lets see so far it is only had one oil leak since Syn was put in.

[amsoilguy]

Actually Amsoil does sell snake oil but not in any large amounts. You statement pertaining to the snake oil sticking to everything does not hold water. I can spray paint the gears and the paint will stick pretty well but I don't think that the product is going to lubricate the parts very well. Sticking to the parts is really not that important in the total picture. Reducing friction, heat and wear are far more important. As for your bike leaking oil after the conversion to Syn: here is why that occurred. Snake oil molecules are different sizes, picture them like a jig-saw puzzle. The molecules create a small amount of friction due to their shape and tend to create a small surface tension area (like a drop of water). There is just enough tension created to prevent the oil from passing through a hole or gap in a seal or gasket. Over time as the gaskets continues to fail the snake oil will flow from the failed seal or gasket. Synthetic molecules are all the same size and shape and once introduced into the engine will more quickly start to flow from the failing gaskets and seals. Good Synthetic oils will not cause a sound engine to leak oil. Your problems was not with the oil it was with your gasket or seal(s) I am not trying to insult you. I am sure your 30 years of experience has made you very knowledgeable about BMW motorcycles and snake oil, however times change. Motorcycle prices have gone up and people want to protect their investment. My biggest challenge is selling Amsoil to any new account is getting the old guys to try something new. They are to set in their ways and will not accept scientific data and customer testimonials.

[tmgs]

Actually Amsoil does sell snake oil but not in any large amounts. You statement pertaining to the snake oil sticking to everything does not hold water. I can spray paint the gears and the paint will stick pretty well but I don't think that the product is going to lubricate the parts very well. Sticking to the parts is really not that important in the total picture. Reducing friction, heat and wear are far more important. As for your bike leaking oil after the conversion to Syn: here is why that occurred. Snake oil molecules are different sizes, picture them like a jig-saw puzzle. The molecules create a small amount of friction due to their shape and tend to create a small surface tension area (like a drop of water). There is just enough tension created to prevent the oil from passing through a hole or gap in a seal or gasket. Over time as the gaskets continues to fail the snake oil will flow from the failed seal or gasket. Synthetic molecules are all the same size and shape and once introduced into the engine will more quickly start to flow from the failing gaskets and seals. Good Synthetic oils will not cause a sound engine to leak oil. Your problems was not with the oil it was with your gasket or seal(s) I am not trying to insult you. I am sure your 30 years of experience has made you very knowledgeable about BMW motorcycles and snake oil, however times change. Motorcycle prices have gone up and people want to protect their investment. My biggest challenge is selling Amsoil to any new account is getting the old guys to try something new. They are to set in their ways and will not accept scientific data and customer testimonials.


hey hey hey . I'm poking ya , you will never believe what oil is in my bike right now, although not in my tranny or final drive <g>

he other thing is, I have been a mmechanic for a long long time, useing Dino Oil has never been a problem in any vehicle car bike of any type , I have only seen one engine failure due to oil problems, and that car had (if I remember correctly 72,000 miles on it , with the original ford oil filter (from the factory they were flat grey back then and that was the only way you could get a ford filter grey then was right from the assembly line)and no record of any oil change ever, that customer had bought 5 lincolns new never serviced any of them and he had the ESP plus service contract, back then it even paid for oil changes,

I'm not syaing amsoil is not better than Dino, just saying there is absolutly nothing wrong with a good dino serviced regularly. Now Gear lugbe well cooler is better yes but in extreeme conditions I prefer Dino gear lube, I have never had a rear or tranny fail on any vehicle i have ever owned except the LT final drive at 52k miles, that was not a oil failure.