purpose of using gear compound when correct backlash is set?
- Thread starter PeteyAce
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When I swapped out my stock diff for an Eaton posi. I just put everything back in the way it came out. I didn't use the compound to check the gear mesh. Probably not the right way to do things, but 2k miles later and I don't have any problems or gear whine.
7-UP BILL
Founding Member
RacEoHolic330 said:
If you use the same gears and NOT change the pinion, you can just reinstall everything. Pinion depth was not altered.
RacEoHolic330 said:
A well manufacutered dif will allow this. Keep production tolerances in mind though.
I will use a theoretical dimension of 4.000" with a tolerance of +/- .005" to make my point. This means the dimension can be anywhere from 3.995" to 4.005" and still pass QA inspection.
Now consider that this part has been in use for several years and is to be replaced. If the old part was 3.995" and the new part is 4.005", then there is a .010" difference between parts. Factor in the build up of production tolerances for each component in multiple part assemblies, and you can get into trouble pretty quick.
The error indroduced with production tolerances is (I think) the main reason for checking the mesh after any change. Plus there is always the off chance of some component being out of tolerance.
Feel free to disagree if you like, I would like to hear your opinions.
jason
txstang84
15 Year Member
vristang said:
very well said...0.010" can wreak havoc in such a situation...if you've got the marking compound, go ahead and use it-the pattern should be a nice long wide CENTERED oval shape...this indicates your backlash is where it needs to be, pinion depth is correct and mesh pattern is dead on where it should be
for everyone else that has had good luck not altering any measurements and just swapping gears or gears and carrier-more power to ya-I'm glad it worked out well for you...just keep in mind some of us are not so "lucky"...I myself have been plagued with rear axle demons since I broke my original rear 10 yrs ago...and the bitch about that is that I sent it to a reputable (at least I believed) shop to have the work done, and then come to find out the a$$wipe that installed my gears set the backlash to double what it was supposed to be, and on top of that didn't put any limited slip additive...I caught that quickly-but not until it had already done damage to my brand spaking new Auburn unit...damn the luck...
sorry to gripe fellas, I know it's wayyyy :OT: but just had to let others know that sometimes it doesn't always work out the way it should for gear swaps...
txstang84 said:very well said...0.010" can wreak havoc in such a situation...if you've got the marking compound, go ahead and use it-the pattern should be a nice long wide CENTERED oval shape...this indicates your backlash is where it needs to be, pinion depth is correct and mesh pattern is dead on where it should be
for everyone else that has had good luck not altering any measurements and just swapping gears or gears and carrier-more power to ya-I'm glad it worked out well for you...just keep in mind some of us are not so "lucky"...I myself have been plagued with rear axle demons since I broke my original rear 10 yrs ago...and the bitch about that is that I sent it to a reputable (at least I believed) shop to have the work done, and then come to find out the a$$wipe that installed my gears set the backlash to double what it was supposed to be, and on top of that didn't put any limited slip additive...I caught that quickly-but not until it had already done damage to my brand spaking new Auburn unit...damn the luck...
sorry to gripe fellas, I know it's wayyyy :OT: but just had to let others know that sometimes it doesn't always work out the way it should for gear swaps...
I don't think there is any need to apologize. When others hear about all the things that some of us have had go wrong, they know what to watch out for later. It sucks that you ended up with damage to your new auburn unit (I love mine by the way), but everyone who reads this thread will think to ask their mechanic if they added friction modifier to the rear fluid. That is what this site is all about.
fiveohwblow
Official Member
- Jul 21, 2005
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Makes me real glad that friction modifier was added when my gear swap was done about 1 week ago....vristang said:
rd
Founding Member
I do both, set it up with gages, etc, and then check the pattern. The pattern check is easy, I use white lithium grease. It verifies that what you did is ok.
Done it without the gage check, and had good luck also, with all SVO parts.
My gage is a ground flat angle across the rear carrier bearing housing, and a dial caliper, so I do the extra check.
Both my 4.10 in my 7.5 and my 4.56 in my 8.8 seem to run quietly.
Done it without the gage check, and had good luck also, with all SVO parts.
My gage is a ground flat angle across the rear carrier bearing housing, and a dial caliper, so I do the extra check.
Both my 4.10 in my 7.5 and my 4.56 in my 8.8 seem to run quietly.
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