Transfer case rebuild tips?
08-25-2020, 08:59 PM
#26
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Tapered roller bearings have three types of forces to deal with: The radial force caused by the gear mesh between mating gear wheels, the axial force caused by the gear mesh (helical) between mating gear wheels and sometimes problematic axle (or shaft) heat expansion. Everything else above is quite easy to calculate but the heat expansion. Heat expansion is difficult as the ambient temperature has a role in it.
If I would be doing the job I would err on the "loose" side on the bearing clearance as I would think the good MB engineers got the calculations right for forces but the data for the heat expansion was wrong.
Also, a too loose bearing does not fail unless it is way too loose and before that happens the gears probably are gone first.
If I would be doing the job I would err on the "loose" side on the bearing clearance as I would think the good MB engineers got the calculations right for forces but the data for the heat expansion was wrong.
Also, a too loose bearing does not fail unless it is way too loose and before that happens the gears probably are gone first.
You also need to account for the type of lubricant and speed of rotation vs various load as well. And we are talking 3/1000s of an inch difference for the tolerance from lose to tight. I think I learned enough to understand that I have no clue. The only thing I can do is check the new bearings and ensure clean and carefull installation.
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08-25-2020, 09:58 PM
#27
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2010 E350 4Matic
Tapered roller bearings have three types of forces to deal with: The radial force caused by the gear mesh between mating gear wheels, the axial force caused by the gear mesh (helical) between mating gear wheels and sometimes problematic axle (or shaft) heat expansion. Everything else above is quite easy to calculate but the heat expansion. Heat expansion is difficult as the ambient temperature has a role in it.
If I would be doing the job I would err on the "loose" side on the bearing clearance as I would think the good MB engineers got the calculations right for forces but the data for the heat expansion was wrong.
Also, a too loose bearing does not fail unless it is way too loose and before that happens the gears probably are gone first.
If I would be doing the job I would err on the "loose" side on the bearing clearance as I would think the good MB engineers got the calculations right for forces but the data for the heat expansion was wrong.
Also, a too loose bearing does not fail unless it is way too loose and before that happens the gears probably are gone first.
FWIW the Indy said that the premature failure after the first rebuild was too tight of clearances. I think that they based that on the distress they saw on the races after the teardown.
Last edited by MBNUT1; 08-25-2020 at 10:02 PM.
08-25-2020, 11:25 PM
#28
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https://www.google.com/url?sa=t&rct=...EcOOCcBuycgmYH
Based on reading this:
Output/input shafts of a transmission are projecta set...aka using expensive equipment to get it right and not think about it during assembly.
How many transmissions a year are being produced (millions), nobody is setting any tolerances for each TC. "Here is the shim, here is bearing press in, next."
Based on reading this:
Output/input shafts of a transmission are projecta set...aka using expensive equipment to get it right and not think about it during assembly.
How many transmissions a year are being produced (millions), nobody is setting any tolerances for each TC. "Here is the shim, here is bearing press in, next."
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08-26-2020, 11:06 AM
#29
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'11 E350, '11 E550, '98 M3, '95 E320
https://www.google.com/url?sa=t&rct=...EcOOCcBuycgmYH
Based on reading this:
Output/input shafts of a transmission are projecta set...aka using expensive equipment to get it right and not think about it during assembly.
How many transmissions a year are being produced (millions), nobody is setting any tolerances for each TC. "Here is the shim, here is bearing press in, next."
Based on reading this:
Output/input shafts of a transmission are projecta set...aka using expensive equipment to get it right and not think about it during assembly.
How many transmissions a year are being produced (millions), nobody is setting any tolerances for each TC. "Here is the shim, here is bearing press in, next."
08-26-2020, 01:40 PM
#30
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2010 E350 4Matic
I wouldn't be surprised if its the "set-right" process, where-in they "accounted" for and controlled the tolerances to eliminate setting clearances. That said, its possible they didn't fully "account" correctly and thus the situation we face. Or what happens often at my job (making helicopters), is a supplier and/or material is changed and the initial inspection/QA doesn't catch the issue and it isn't till later during a test/acceptance procedure the component fails or causes a failure.
When I hear people saying that they think the bearing is undersized that speaks to an engineering issue design or management.
Last edited by MBNUT1; 08-26-2020 at 01:56 PM.
08-26-2020, 02:06 PM
#31
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2010 E350 4Matic
Tapered roller bearings have three types of forces to deal with: The radial force caused by the gear mesh between mating gear wheels, the axial force caused by the gear mesh (helical) between mating gear wheels and sometimes problematic axle (or shaft) heat expansion. Everything else above is quite easy to calculate but the heat expansion. Heat expansion is difficult as the ambient temperature has a role in it.
If I would be doing the job I would err on the "loose" side on the bearing clearance as I would think the good MB engineers got the calculations right for forces but the data for the heat expansion was wrong.
Also, a too loose bearing does not fail unless it is way too loose and before that happens the gears probably are gone first.
If I would be doing the job I would err on the "loose" side on the bearing clearance as I would think the good MB engineers got the calculations right for forces but the data for the heat expansion was wrong.
Also, a too loose bearing does not fail unless it is way too loose and before that happens the gears probably are gone first.
08-26-2020, 06:02 PM
#32
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The transfer case on these cars may have a design flaw that cannot be fixed, i.e. for the proper gear mesh bearing clearance must be set to certain limits but then this same clearance it too tight for the fully warmed up gear box and leads to bearing failure.
From the two options I would chose the clearance that keeps gear mesh working correctly and this is why I suggest checking if there is a stronger bearing with the same physical dimensions so the bearing could last a bit longer under too tight clearance setting that is required for the proper gear mesh function.
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09-28-2020, 07:02 PM
#34
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Car is fixed and more updates back at the same place. A small set back due to leaks.
https://mbworld.org/forums/glk-class...anny-diff.html
https://mbworld.org/forums/glk-class...anny-diff.html
10-06-2020, 12:40 PM
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gl 450, S 430
Just did this on my GL 450. Some say it's a middle of the road type repair, not difficult, not easy. I'd say it's a pain to get out because of the three bolts at the top of the TC. My chain was skipping teeth. If you get the whole thing done in five hours, good on ya!
10-06-2020, 12:58 PM
#36
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We have rebuild Cayenne TC (stretched chain and clutches), which is a process. The nice part is you can take TC out and work on it. On GLK/E/S etc. some parts are in the tranny housing which makes it extra PITA.
10-06-2020, 01:15 PM
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gl 450, S 430
163k, that 4.7L has a lot of torque, and it's been skipping for a while. The chain that stretches, only stretches a 1/2 - 3/4 inch, that's all it takes. Do you know the fluid to use? Can I use Mobil 1 Trans fluid? Also, for the Rear Diff and Front Diff, what's the fluid, may as well change them all.
10-06-2020, 02:39 PM
#38
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163k, that 4.7L has a lot of torque, and it's been skipping for a while. The chain that stretches, only stretches a 1/2 - 3/4 inch, that's all it takes. Do you know the fluid to use? Can I use Mobil 1 Trans fluid? Also, for the Rear Diff and Front Diff, what's the fluid, may as well change them all.
