I broke my second dana 70 this week, but I found a complete one that is in decent shape, just needs a pinion seal. Can I replace the seal without pulling the pinion out? It looks like I could take the pinion nut and the yoke off to get to the seal. I really don't feel like taking the cover off, taking the shafts out, and taking the carrier out just to take the pinion out and then put it all back together. Do I have to check backlash if I can get the new seal in without taking the whole axle apart? Also, what is the torque spec on the pinion nut? I've heard 150 ft/lbs and then back off 120*.

 

yes. u can change that seal pretty easy. just pull the nut.

 

Before you replace the seal, check the axle-vent.

My bet is that the vent is plugged and forcing grease out the seal.

Many is the pinion-seal that has been replaced on account of a plugged vent.

Usually, un-stopping the vent will stop the pinion-seal leak.


To answer your question, to replace the seal, remove the drive-shaft yoke, take off the pinion-yoke nut, slide out the pinion-yoke, pry off the old seal, drive in the new, slip the yoke back on, replace the big nut, tighten = REAL TIGHT, replace the shaft, and done.

Don't use an impact wrench.

 

Be careful tightening the pinion nut. I've set up alot of diffs an this is how I do it. There is a specific torque value for the pinion bearing preload resistance but you can do it by feel.
You want to set up the pinion bearing preload properly. To loose and the seal will leak, to tight and you'll cook the pinion bearings (another diff). Tighten the nut and remove all the in and out movement or play from the pinion gear. Go slow, you don't want to go to far. Rotate the gear a little. You just want to feel the back lash play. When you feel the back lash after there is no more in and out movement tighten the nut untill you feel a bit of drag (1/8th of a turn at a time). The ring gear or axles should not be turning when you feel this drag just the slight rotation of the back lash between the pinion and ring gear. Once you feel this drag you'll want to tighten it a bit more. I'm not sure if these diffs have a crush sleeve but you don't want to go to far you just want to feel a good amount of drag. For example- when it its set, when you first start to rotate the pinion it will feel like its is slightly stuck but when it is moving it will have a bit of drag or resistance. You want more drag that you think. Everything will go loose when it warms up. That is why you want to have a pretty stiff preload.
Good luck I hope this helps.

 

No crush sleeve on a d70, just select-fit shims to determine pinion depth. It is recommended to use a new pinion nut, but I've had several off and back on with no problems. I usually go ''2 foot cheater bar'' tight, though I'm sure there's a proper torque value

 

thanks for the help! does anyone know a part number for the pinion seal? My local parts store only has the seal for a 9.25 chrysler rear in stock. also does anyone have a torque value other than really tight for the pinion nut? thanks again for all your help.

 

As already said, it is recommended procedure to use a new nut, whenever it is removed.

This is on account of the nut is one of those "locking" steel nuts, the type that has the outer couple of threads sort of smashed.

It would be a good idea to sort of re-smash those threads, a little, before re-using an old nut.


I say this because I once had the yoke-nut on a NP-205 (same type nut - opposite end of drive-shaft) to come loose, while pulling a gooseneck full of cattle.

When this happened, just as the yoke splines were about to slide apart, the drive-shaft started "kicking" real HARD, bursting the bell-housing.

The nut was still trapped within the shaft/yoke assembly.

I had to replace the bell-housing, all on account of a silly little nut.