Gear Rattle After Install of Aluminum Flywheel - Possible Fix?
01-10-2010, 04:08 PM
#1
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Using Gear Oil in a T3650 - Possible Gear Rattle Fix?
Recently, my stock T/O bearing started making noise so I opted to replace the clutch and flywheel. I went with the SPEC Stage 2 clutch and the SPEC Billet Aluminum Flywheel.
Due to the installation of the lightweight flywheel, I'm now experiencing gear rattle that I find extremely annoying. I've since read posts of other vehicle owners (Mustang, Audi, etc.) experiencing this same thing so I know it's normal. For those that don't know, the sound has been compared to that of a coffee grinder. I only hear it at idle and after the car has warmed up some.
In my quest for knowledge on the subject, I came across an article from a BMW shop that both explained the issue (Gear Rattle Article) and another by them offering a solution (Possible solution).
If you take the time to read the solution article, it states they have had success using a mix of Redline D4 ATF and 75W-140NS gear oil as the gear oil acts as a dampener on the gear rattle. After reading up on the Redline products, I'm thinking this could very well cure my gear rattle problem in my T3650. Both oils are suitable for synchros and the heavier gear oil contains no LS friction modifiers. I'm thinking of trying this out. Tell me, am I nuts?
Thanks for reading.
Due to the installation of the lightweight flywheel, I'm now experiencing gear rattle that I find extremely annoying. I've since read posts of other vehicle owners (Mustang, Audi, etc.) experiencing this same thing so I know it's normal. For those that don't know, the sound has been compared to that of a coffee grinder. I only hear it at idle and after the car has warmed up some.
In my quest for knowledge on the subject, I came across an article from a BMW shop that both explained the issue (Gear Rattle Article) and another by them offering a solution (Possible solution).
If you take the time to read the solution article, it states they have had success using a mix of Redline D4 ATF and 75W-140NS gear oil as the gear oil acts as a dampener on the gear rattle. After reading up on the Redline products, I'm thinking this could very well cure my gear rattle problem in my T3650. Both oils are suitable for synchros and the heavier gear oil contains no LS friction modifiers. I'm thinking of trying this out. Tell me, am I nuts?
Thanks for reading.
Last edited by StripeyGT; 01-10-2010 at 07:09 PM.
01-10-2010, 07:52 PM
#3
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If I were to try it I would sneak up on it and use 0.5qt of the gear oil and 2.7qts of ATF at first (the recommend fill is 3.2qts per this TSB, the '05+ service manuals all say 3.2qts too).
The 3650 was built to run ATF, you could end up fixing the rattle and frying the synchros or a bearing--the heavier oil will run the ball bearings hotter.
The 3650 was built to run ATF, you could end up fixing the rattle and frying the synchros or a bearing--the heavier oil will run the ball bearings hotter.
01-10-2010, 08:08 PM
#4
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Thanks for the feedback cliffyk. I was hoping you would have a comment.
Interestingly enough, the D4 ATF is rated at 70W80 already. Sounds heavy, but it really isn't, as you know (the SAE motor oil rating equivalent per Redline is 0W-20). I'm thinking adding the 75W140 won't make that much of a difference to the bearings, especially since it would be a roughly 50/50 mix with the ATF. That, and these oils are formulated for service manual transmissions.
Interestingly enough, the D4 ATF is rated at 70W80 already. Sounds heavy, but it really isn't, as you know (the SAE motor oil rating equivalent per Redline is 0W-20). I'm thinking adding the 75W140 won't make that much of a difference to the bearings, especially since it would be a roughly 50/50 mix with the ATF. That, and these oils are formulated for service manual transmissions.
01-11-2010, 05:45 PM
#5
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Thanks for the feedback cliffyk. I was hoping you would have a comment.
Interestingly enough, the D4 ATF is rated at 70W80 already. Sounds heavy, but it really isn't, as you know (the SAE motor oil rating equivalent per Redline is 0W-20). I'm thinking adding the 75W140 won't make that much of a difference to the bearings, especially since it would be a roughly 50/50 mix with the ATF. That, and these oils are formulated for service manual transmissions.
Interestingly enough, the D4 ATF is rated at 70W80 already. Sounds heavy, but it really isn't, as you know (the SAE motor oil rating equivalent per Redline is 0W-20). I'm thinking adding the 75W140 won't make that much of a difference to the bearings, especially since it would be a roughly 50/50 mix with the ATF. That, and these oils are formulated for service manual transmissions.
The 3650 uses composite synchro rings made of materials much like the clutches in automatic transmissions (often referred to as "cardboard" or "paper")--not bronze or brass as was common back when--and this is much of the reason why ATF is the recommend lubricant (I used to run ATF in the trannies of my 2-stroke dirt bikes, it provided a much more crisp feel and performance for the wet clutches).
For this reason I would have some concern about making the ratio of "plain ol' gear oil" too high...
01-11-2010, 07:04 PM
#6
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Just wondering, but is the "gear rattle" you're describing a totally different thing than clutch chatter (like when engaging 1st or reverse slowly and without giving the gas pedal any play)? I get a little of that since the clutch has passed it's "break in" period (per SPEC's instructions), but I was told by one of the guys at GTR to expect that, especially with an aluminum flywheel.
01-11-2010, 07:30 PM
#7
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There are a number of possible noises, rattles, rumbles, and other oddities associated with lightened rotating drive train components--if there were not the OEM parts would be lighter as it would improve fuel economy. But as much as fuel efficiency is a priority in the OEM world, NVH control takes precedence...
01-11-2010, 08:44 PM
#8
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The 3650 uses composite synchro rings made of materials much like the clutches in automatic transmissions (often referred to as "cardboard" or "paper")--not bronze or brass as was common back when--
For this reason I would have some concern about making the ratio of "plain ol' gear oil" too high...
For this reason I would have some concern about making the ratio of "plain ol' gear oil" too high...
Just wondering, but is the "gear rattle" you're describing a totally different thing than clutch chatter (like when engaging 1st or reverse slowly and without giving the gas pedal any play)? I get a little of that since the clutch has passed it's "break in" period (per SPEC's instructions), but I was told by one of the guys at GTR to expect that, especially with an aluminum flywheel.
01-11-2010, 08:57 PM
#9
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My '03 has had a sort of mainshaft bearing rattle/rumble in the tranny, in neutral with the clutch engaged since I got it (on 12/7/2006) with 30k miles on it.
I've got 100k on it now and it has not changed for better or worse--I can imagine how less dampening of the engine's power pulses could amplify and alter that noise...
I've got 100k on it now and it has not changed for better or worse--I can imagine how less dampening of the engine's power pulses could amplify and alter that noise...
