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  #1  
Old 03-28-2000, 02:44 PM
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Join Date: Oct 1999
Location: New York City Burbs
Posts: 177
What is more important: the friction measurement of the installed pinion & bearings OR the torque of the pinion shaft nut?

My situation is one where If I torque down to specs there will be an unreasonable amount of drag on the pinion.

Also, how the does one stretch the differential housing (to get the diff/ring gear out) without having the factory stretcher/jigs? I was thinking about a small "Porta Power" in the rear case to satretch that .2mm or less. Any suggestions?
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  #2  
Old 03-28-2000, 10:01 PM
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Join Date: Mar 1999
Location: Suwanee, GA, USA
Posts: 4,712
There is a crush washer that has to be replaced every time you take it apart.
I hope MB DOC sees this, for he has done this many times.


------------------
Benzmac:
1981 280GE SWB
1987 16V
ASE CERTIFIED MASTER AUTO TECHNICIAN
SERVICE MANAGER FOR 14 BAY FACILITY
MERCEDES SPECIALIST 8 YRS
PARTNER IN MERCEDESSHOP.COM


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  #3  
Old 03-29-2000, 07:34 PM
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Join Date: Jan 2000
Location: New Bedford, MA USA
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The backlash between the ring and pinion must be set while torquing the pinion retainer nut. Backlash translates to ring and pinion clearance. The crush sleeve that Benzmac refers to is the component which maintains the correct clearance. You need dial indicators to set these components correctly. If you overtighten the pinion nut, you will have to get another crush sleeve as it will now be shorter than it should be and will give excessive clearance and you will need to start over again. If you are trying to reuse the one that's there now, you will overtighten the pinion and squeeze the hell out of the pinion bearings, leading to excessive backlash, "friction" and early bearing failure. This type of repair requires a knowledgable, experienced mech to complete successfully. BTW, what is the problem with this rear end???

------------------
Jeff L
1987 300e
1989 300e
1987 BMW 325

[This message has been edited by jeffsr (edited 03-29-2000).]

[This message has been edited by jeffsr (edited 03-29-2000).]
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  #4  
Old 03-29-2000, 10:00 PM
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Join Date: Mar 1999
Location: Tucker, Ga USA
Posts: 12,153
The most important thing is preload on bearings, too tight or loose will result in bearing failure! If you can get at least 40-50 ft/lbs of torque on nut & not have too much preload on bearings the rear should be OK. This is why many rear ends fail after pinion seal replacement. Use in/lb torque wrench to check & set-up preload.

Missed question about side bearing preload, again the preload on the diff bearing are critical also. have set-up at least 100 MB rears & never used case "stretcher".
There are at least 4 different rears that Benz has used, what year & model car?

------------------
MERCEDES BENZ MASTER GUILD TECHNICIAN
ASE MASTER TECHNICIAN
27 YEARS DEALER M.B. Shopforeman
190E 2.3 ITS RACECAR
1986 190E 16V

[This message has been edited by M.B.DOC (edited 03-29-2000).]
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  #5  
Old 03-30-2000, 12:54 AM
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The only proper way to set up the pinion bearings is with a new crush sleeve and by tightening (crushing) the bearing inner races till the bearings are tight to an exact amount 10-15inlbs if I remember correctly. This is the force to spin slowly the pinion without the ring gear installed. Just the drag of the tightened bearings.

A proper set-up would then measure pinion depth and everything would be taken back apart and the depth altered by shimming.

Next the carrier preload would be determined and the carrier installed for back lash measurement. I would not vary back lash by change pinion depth. I would do it by moving the carrier side to side with shims.

In practice these methods are very seldom used. Proper pinion depth tools cost thousands of dollars and are differential specific. The original set up is usually used with the proper bearing set-up and a white lead or prussian blue contact pattern is taken and read. Gross errors in pinion depth are corrected otherwise its accepted and backlash is corrected.

------------------
Steve Brotherton
Owner 24 bay BSC
Bosch Master, ASE master L1
26 years MB technician

[This message has been edited by stevebfl (edited 03-29-2000).]
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  #6  
Old 03-30-2000, 01:33 PM
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Location: New York City Burbs
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Thanks for your response. It appears the pinion bearing s are shot. This is an 84 190E with a 2.3, automatic. About four months ago, I changed the pinion seal while I was replaving all the driveshaft rubber, and I had the tranny out to replace the rear main seal. With the pinion seal replacement, I only did the seal. If I'm reading the responses correctly, it seems One has to dismantle the entire rear end to replace that crush sleave spacer. This I did not do at that time. I must have went too heavy on that pinion nut which lead to the failure of the bearings. I had the whole thing out with the intention of rebuilding ( I have done a few Porsche 944 transaxles) but have already ordered a junkyard differential unit. On a rainy day I would still like to fix the spent rear. I'm no pro, but a decent shadetree mechanic. I would have put the pinion in with new bearings & spacers/sleeves and then some blue goo to see where on the teeth the ring & pinion were mating. I was surprised to see the post that a "spreader" isnt required, like the CDROM Mercedes shop manual suggests. In disassembling, I went as far as the flange seals (radial). It was late and the circlips were giving me a headache. Only then I read the manual to see that there is a decent amount of load on the circlip.

Pat Leber
83,84,85.5 Porsche 944
84 MB 190E 2.3 auto

quote:
Originally posted by M.B.DOC:
The most important thing is preload on bearings, too tight or loose will result in bearing failure! If you can get at least 40-50 ft/lbs of torque on nut & not have too much preload on bearings the rear should be OK. This is why many rear ends fail after pinion seal replacement. Use in/lb torque wrench to check & set-up preload.

Missed question about side bearing preload, again the preload on the diff bearing are critical also. have set-up at least 100 MB rears & never used case "stretcher".
There are at least 4 different rears that Benz has used, what year & model car?



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  #7  
Old 03-30-2000, 01:49 PM
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Join Date: Oct 1999
Location: New York City Burbs
Posts: 177
Thanks for responding Steve. Its always interesting to hear that the real practice is not as agonizing as the factory manual methods!

I went too tight on the pinion nut when I did the seal a few months ago, which killed the pinion bearings. Thanks for the advice on the set up. I dont have an elaborate dial indicator & adaptors. Since I needed the car back together in a hurry, (my wife's ride) I got a used diff unit to slap back in there. I dont want her abusing my 944! Since I'm using a used one, chances are that i'll be down this road again very shortly, therefore I plan on redoing the rear that sitting on on my workbench.

Thanks again.

Pat Leber
83,84,85.5 Porsche 944
84 MB 190E 2.3 auto


quote:
Originally posted by stevebfl:
The only proper way to set up the pinion bearings is with a new crush sleeve and by tightening (crushing) the bearing inner races till the bearings are tight to an exact amount 10-15inlbs if I remember correctly. This is the force to spin slowly the pinion without the ring gear installed. Just the drag of the tightened bearings.

A proper set-up would then measure pinion depth and everything would be taken back apart and the depth altered by shimming.

Next the carrier preload would be determined and the carrier installed for back lash measurement. I would not vary back lash by change pinion depth. I would do it by moving the carrier side to side with shims.

In practice these methods are very seldom used. Proper pinion depth tools cost thousands of dollars and are differential specific. The original set up is usually used with the proper bearing set-up and a white lead or prussian blue contact pattern is taken and read. Gross errors in pinion depth are corrected otherwise its accepted and backlash is corrected.



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  #8  
Old 03-30-2000, 01:56 PM
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Join Date: Mar 2000
Location: Gainesville FL
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I would think that the spreader would be necessary. We built one ourselve out of half inch think steel and an old puller. I can't imagine getting enough spacers in the carrier bearing preload without the room given by stretching. It will come apart (without stretching) though. If you can get the original pack back in with the original bearings then use the same stack and try it. Your preload will be close enough and you will just have to move shim thicknesses to get your back lash.

As to pinion seals, I use a chiesel to mark a line across the shaft and nut. On reassembly I tighten till the marks line up assuring no futher crush.

------------------
Steve Brotherton
Owner 24 bay BSC
Bosch Master, ASE master L1
26 years MB technician

[This message has been edited by stevebfl (edited 03-30-2000).]
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  #9  
Old 03-30-2000, 05:21 PM
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Join Date: Aug 1999
Location: Florida / N.H.
Posts: 8,777
quote:
Originally posted by stevebfl:
I would think that the spreader would be necessary. We built one ourselve out of half inch think steel and and old puller. I can't imagine getting enough spacers in thecarrier preload with the room given by stretching. It will come apart though. If you acn get the original pack back in with the original bearings then use the same stack and try it. Your preload will be close enough and you will just have to move shim thicknesses to get your back lash.

As to pinion seals, I use a chiesel to mark a line across the shaft and nut. On reassembly I tighten till the marks line up assuring no futher crush.



I have had luck doing that. It should be noted that many diff. leaks that are blamed on seals and gaskets are caused by an often over-looked plugged vent pipe.

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  #10  
Old 03-30-2000, 10:19 PM
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Join Date: Mar 1999
Location: Tucker, Ga USA
Posts: 12,153
Don't know how many tech's have ever built rear end, I'm sure it's less than 1%. Most shops want to "replace" with used or rebuilt because of failure. Most failures are from improper preload!! Preload on side carrier bearings is critical, some of us old guys know a lot af secrets on set-up.

------------------
MERCEDES BENZ MASTER GUILD TECHNICIAN
ASE MASTER TECHNICIAN
27 YEARS DEALER M.B. Shopforeman
190E 2.3 ITS RACECAR
1986 190E 16V
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  #11  
Old 05-23-2000, 02:00 PM
Igor
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Depth gauges are used to determine the shim stacks for both: pinion & ring gears. Then, a drag check is done to both independently. When reassembled, blue is used to verify gear print. Box is again reassembled after cleaning the blue and the backlash is recorded. If all parameters are within speck, the final drag check of a compleate assembly is done. If you're lucky, the gearbox will be dissassembled & reassembled only three times during this procedure. This is not from MB, this is how Robinson R22 & R44 helicopter main & tail gearboxes are done.
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