Differential leak - Page 3 - PeachParts Mercedes-Benz Forum

psaboic · #31 06-02-2019, 11:24 AM

Quote:

Originally Posted by vox_incognita

Please read carefully the .pdf.

"Tightening torque of slot nut should amount to at least 180Nm.If this minimum tightening torque is not attained etc..."

https://www.startekinfo.com/StarTek/outside/12265/disc_2/program/Chassis/35-530.pdf

The 30-40 and 200Nm values concern the propshaft,not the pinion nut.

I'd check carefully other threads on peachpart.com on this topic.

Your right, it does concern the propshaft not the pinion nut.......Looked at other threads and no real mention of the torque of the nut (although I do realize it is different in each case) but it would be nice to know a ballpark on what to expect. Also I am still contemplating if I want to attempt this with the differential in place or if I should pull it to get more working room. Anybody have any suggestions.

Diesel911 · #32 06-02-2019, 11:21 PM

This has the minimum torque on the Shaft Nut is 180Nm. But, that is the slotted nut and it does not mention if the newest type of nut is different or not.

Diesel911 · #33 06-02-2019, 11:23 PM

In the manual it has the 3 piece drive shaft having a rear torque of 200Nm. I believe your drive shaft is a 2 piece driveshaft.

psaboic · #34 06-02-2019, 11:33 PM

Yep, it is a two piece shaft. 180Nm converts to about 132 Ft/Lbs. Not a lot, but still quite a bit. Gonna try doing the job with the differential installed in the car first. If that does not pan out, I guess I will drop the differential and try to do it in the garage.

If anyone has done a pinion seal with the diff in the car, please chime in with your experience.

Thanks

vox_incognita · #35 06-03-2019, 02:25 AM

FWIW this is the German version (basically the same thing).

Given the pinion shaft is the same ,the flange is the same..what would make the double hex nut produce the same clamping force(resulting in the same required bearing friction value) at nearly fives time lower torque ? :-)

Anyway:
-I'd mark the position of the nut in relation to the pinion shaft before loosening and have a spare nut,they're cheap.
-make sure the brakes do not drag during some full rotations(may need to remove this and that).
-drain the diff fluid

You may or may not opt in to measure friction resistance. If I decided to go that way,I'd do it carefully more than once and record. I'd loosen the nut and tighten it back to say 120Nm. Measure again and record.
After installing the new seal I'd tighten to 120Nm again first ...and measure the friction torque. I'd expect it to be higher than what it was with the old seal. I'd add this difference to the final desired friction torque I need to obtain by further tightening carefully the nut in small increments and carefully measuring the friction torque until the desired result.

Some people have done it going by the mark only(must have used the old nut). Some went the friction measurement way (I remember somebody stating the torque the new seal would add to the final value).
I also remember that if you go by the mark method and the torque value is lower than the recommended to just leave it that way(as the crush sleeve is already compressed).

Never done it but I'd have to one day.
Read the threads on this site:
https://www.google.com/search?as_q=pinion+seal&as_epq=&as_oq=&as_eq=&as_nlo=&as_nhi=&lr=&cr=&as_qdr=all&as_sitesearch=http%3A%2F%2Fwww.peachparts.com%2Fshopforum&as_occt=any&safe=images&as_filetype=&as_rights=#ip=1

https://www.google.com/search?q=pinion+seal+site:http://www.peachparts.com/shopforum&lr=&source=lnms&tbm=isch&sa=X&ved=0ahUKEwjf18301MziAhUIP6wKHe3NCWAQ_AUIESgC&biw=1280&bih=646

I hope somebody with more experience will chime in.

Diesel911 · #36 06-03-2019, 11:47 AM

Quote:

Originally Posted by psaboic

Yep, it is a two piece shaft. 180Nm converts to about 132 Ft/Lbs. Not a lot, but still quite a bit. Gonna try doing the job with the differential installed in the car first. If that does not pan out, I guess I will drop the differential and try to do it in the garage.

If anyone has done a pinion seal with the diff in the car, please chime in with your experience.

Thanks

I have not done the Pinion Seal replacement but I have removed my Differential from the Subframe.

when it came time to re-install the differential even with a transmission Jack I had an extremely hard time getting the bolts the Studs to line up with the holes in the sub frame.

I have no definitive reason why that happened. My best guess is that when I removed the Differential that the subframe (30+ years of stress on it) warped just enough to allow the alignment of the holes to be off.

Anyway it brings up an other issue that the Differential is heavy making it difficult for one person to deal with in the space under the Car. Also once the differential Studs are in the holes I could not see holding the differential up in position while I put the nuts on the studs. So you would need some sort of jack to hold it up in position.

With the Driveshaft removed there ought to be plenty of room there should be room to change the seal.

hercules · #37 06-03-2019, 01:37 PM

Don"t make things harder than they have to be. Open the holes a small amount.
Wasted hours trying. If you must pry the differential out,your"re not
going to get it back in. Needed to do this on a few but not all.

psaboic · #38 06-04-2019, 09:31 AM

Well, the socket I ordered should be here today, so after work I will go out and try to measure the turning torque and report back what I got. Right now the diff is drained, the brake calipers and rotors are off, but the axles are still attached. I'll make sure they are as level as possible when I measure the torque.

psaboic · #39 06-04-2019, 03:51 PM

Just got a call from a friend of mine. He is parting out his wrecked 1985 300D and offered to hold on to the diff in case I wanted it. Would it fit ok in a 1983 if I wanted it as a spare? I seem to recall there was something unique about a 1985 differential, different gear ratio possibly?

Diseasel300 · #40 06-04-2019, 03:58 PM

1985 is a 2.88:1. It'll fit, but you'll need the speedo from the '85 if you expect the speed to be anything close to accurate.

psaboic · #41 06-04-2019, 05:00 PM

True, the Speedo would be off a bit. I'm pretty sure my stock 1983 diff is 3.07 ratio, so with a 2.88 it shouldn't be too much different.

psaboic · #42 06-04-2019, 11:14 PM

Ok, first update. I got the 30MM 12 point socket today, and measured the turning torque on the pinion flange nut. With the differential drained, brake calipers and rotors removed, and axles jacked up to level, the clockwise turning torque was 5 in/lbs or about 55 Ncm. It was the same torque reading when I turned it counter clockwise. I measured it 3 times in each direction and got the same reading each time.

So, it seems that my bearings are definitely worn. If I mark the nut before removing it I could set it back to 55 Ncm after replacing the seal and just drive it. Or would it be a good idea to try to set the turning torque to 75-100Ncm after replacing the pinion seal.

vox_incognita · #43 06-05-2019, 07:02 AM

You might find this useful as a reference info(page 4):

https://www.startekinfo.com/StarTek/outside/12265/disc_2/program/Chassis/35-550.pdf

It is for pinion shaft only . Note the "drop" in fr.torque for run-in bearings and the specified permissible values (50-100Ncm).
Now I have no idea how the mass of the differential ..inertia etc...(in your case) would affect the reading and what kind of measuring device you used but you might be well in spec. (I'd do the rotation part as slooow as possible but I can imagine how difficult it can be with the setup not removed from the car..).
I proposed in my previous post measuring before removal of old seal and after installation of the new one with the nut tightened @ a given torque value in hope to determine the friction torque the new seal would add to the total value.
I'd mark the position of the nut in either case.

Probably adding 25-30% (70-ish Ncm final) would not hurt.

Wish someone experienced would join the thread !

psaboic · #44 06-05-2019, 09:39 AM

Vox.......Thank you for the link. Yes, it was a bit of a pain doing it in the car but it as do-able. That is one of the reasons I did it three times in both directions. I agree that marking the nut and proceeding is my best next move. Also, you must have read my mind as I was thinking about measuring the torque value on the nut now (with the old seal still in) and then setting it to the same torque after putting in the new seal and measuring rotational torque to see the change.

vox_incognita · #45 06-05-2019, 10:02 AM

This IMHO should be done @ a value less than the min. perscribed 180Nm. The nut now might be >200Nm...
I'd slacken,tighten back to say 130Nm and measure. Remove the old seal& install the new one...tighten to 130Nm...measure the friction torque with the new seal...add the difference X to the final reqired fr. torque value(55Ncm+XNcm+some little more if you feel like it)...continue tightening the nut in small increments until reaching it.
Might be an overkill but it would be interesting to see how the new seal affects it.