Changing oil in a 742 differential.

[A/C guy]

68 Dart GTS with a 742 differential. I'm changing out the leaking pinion seal and want to drain all of the 50+ year old oil at the same time. There is a plug on the side of the carrier @ about the centerline of the pinion. I assume this it the fill port. Some oil drained out when I pulled the seal, how do I remove the remainder? To refill, should I go with the Chrysler oil and friction modifier (have the P/Ns), or is there something off the shelf that is just as good? And last, can someone confirm what the pinion nut torque is? Think it is 230 or 240 ft. lbs. Thanks in advance.

 

[Syleng1]

Sadly removing the carrier (pig) is the only option to a true cleaning. No 8-3/4 of mine have that ability either.

 

[Demonracer]

230-240 lb ft torque on the pinion nut, in order to get all of the old oil out you will have to pull the carrier. Get yourself a factory service manual & it will answer most of your questions. You will need the friction modifier If yours have a clutch type carrier.

 

[Demonic]

You could pull it all out with a vacuum jar and a vinyl hose shoved to the bottom of the housing through the fill plug, but any accumulated debris would likely still be on the bottom. If you remove the center section, most folks replace the inner axle seals at the same time. Don’t over-grease the axle bearings, it can push past the outer seals between the retaining flange and the bearing.

 

[mderoy340]

drill a hole in the bottom of the housing just outboard of the weld seam running fore and aft. Tap for 1/8"NPT and put a drain plug in it.