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Hipine · 09-23-2004, 02:31 PM

I don't know about the diesel. That damper on the rear driveshaft might cause problems. But on my 280GE the speedometer drive can be removed without touching the driveshaft. You can look for yourself though and see if you can get past the damper.

In order to remove the speedo drive you need only disconnect the speedometer cable, remove the four bolts (I don't remember if they're 8 or 10mm heads) that hold it to the transfer case, and withdraw the unit straight back about 20mm to disengage the shaft. There aren't any fiddly parts. If the shaft/gear at the center of the drive falls out while you're removing it, just clean everything up good and push it back in before replacing the unit.

I've pulled these off of 4 or 5 t-cases and never found a gasket under one of them....nor in any other part of the transfer case for that matter. They're all sealed with a liquid sealant. There is an MB part number for the sealant, but on the speedo drives I've been using "Hylomar HPF" from Permatex brand, available at most big auto parts chains now. It's a non-hardening flange sealant that is oil resistant and even seals through oil so the surfaces need not be perfectly clean.

It's easiest to do this job at the same time you're replacing your diff fluid, since there is an oiling port to the speedo drive that is below the standard oil level so that if you remove the speedo drive with the t-case full of oil, oil will weep out that hole until you put the drive back. If you do the re-seal during a fluid change, you can do it while the t-case is empty and avoid the leakage. The last time I changed a speedo drive I was in a hurry so I just coated the drive body sealing edge with Hylomar ahead of time, pulled the old drive body, and held my finger over the oil hole while I wiped the back of the t-case clean, and then quickly popped the new speedo drive into place. A little oil leaked while I was placing the cover, but the Hylomar sealed it all up okay.

Sorry to ramble so much. If you're unlucky and it looks like the damper will prevent you from pulling the speedo drive body straight back 20mm, then just remove the rear DS and the damper from the t-case output flange, marking them in place first as Harald said. It should really be only about an hour job from start to finish, and the biggest part of the time will be spent on all those drive shaft nuts. Best to use new nuts when putting the drive shaft back on too, though I've re-used old ones with no problems before.

Good Luck!

-Dave G.

09-23-2004, 02:31 PM	#7 (permalink)
Hipine BenzWorld Elite Date registered: Nov 2002 Vehicle: 1980 LWB 280GE Location: Bailey, CO, USA Posts: 3,504	RE: oil pan / drivetrain leaks I don't know about the diesel. That damper on the rear driveshaft might cause problems. But on my 280GE the speedometer drive can be removed without touching the driveshaft. You can look for yourself though and see if you can get past the damper. In order to remove the speedo drive you need only disconnect the speedometer cable, remove the four bolts (I don't remember if they're 8 or 10mm heads) that hold it to the transfer case, and withdraw the unit straight back about 20mm to disengage the shaft. There aren't any fiddly parts. If the shaft/gear at the center of the drive falls out while you're removing it, just clean everything up good and push it back in before replacing the unit. I've pulled these off of 4 or 5 t-cases and never found a gasket under one of them....nor in any other part of the transfer case for that matter. They're all sealed with a liquid sealant. There is an MB part number for the sealant, but on the speedo drives I've been using "Hylomar HPF" from Permatex brand, available at most big auto parts chains now. It's a non-hardening flange sealant that is oil resistant and even seals through oil so the surfaces need not be perfectly clean. It's easiest to do this job at the same time you're replacing your diff fluid, since there is an oiling port to the speedo drive that is below the standard oil level so that if you remove the speedo drive with the t-case full of oil, oil will weep out that hole until you put the drive back. If you do the re-seal during a fluid change, you can do it while the t-case is empty and avoid the leakage. The last time I changed a speedo drive I was in a hurry so I just coated the drive body sealing edge with Hylomar ahead of time, pulled the old drive body, and held my finger over the oil hole while I wiped the back of the t-case clean, and then quickly popped the new speedo drive into place. A little oil leaked while I was placing the cover, but the Hylomar sealed it all up okay. Sorry to ramble so much. If you're unlucky and it looks like the damper will prevent you from pulling the speedo drive body straight back 20mm, then just remove the rear DS and the damper from the t-case output flange, marking them in place first as Harald said. It should really be only about an hour job from start to finish, and the biggest part of the time will be spent on all those drive shaft nuts. Best to use new nuts when putting the drive shaft back on too, though I've re-used old ones with no problems before. Good Luck! -Dave G.