Pinion seal replacement (?)

[BB72Chally]

Ok, bought a 742 case, 3.55:1 ratio posi from Mancini, along with a balanced 7290 yoke driveshaft assembly. Everything's great, did the break in procedure that Mancini insisted upon along with the recommended lube. The problem is, the front pinion seal leaks like a sieve.
(fast forward) talked to Mancini, they were pretty good, they sent me a new seal and a yoke tool. Checked the FSM, it appears that I can replace the seal in place if I do a rolling torque spec prior to disassembly. After installing the new seal (assuming the yoke is ok, burrs ,etc) then I torque the pinion nut to 170 ft lbs. Then check the rolling torque. Tighten the pinion nut as needed and do constant rolling torque checks until the spec is the same. 

Does that sound about right? Am I missing something?

I'm thinking no impacts or sledge hammers.

[Chryco Psycho]

sounds right to me

[tactransman]

 

[BB72Chally]

thanks guys!!

[crcarch]

I have to replace my pinion seal as well.  Is there only an outer seal or does it have two like the axle bearings? Does the pinion bearing need grease, or is it lubricated by the gear oil?

Thanks in advance.

[tactransman]

One seal and it is lubed by the rear end gear oil.

[crcarch]

One seal and it is lubed by the rear end gear oil.

Thanks!

[crcarch]

I look at my last entry date and realize I've been way too busy.

Got everything cleaned and repainted.  Place the carrier back into the axle housing.  Pressed in the seal and placed the yoke over the pinion gear. (First, Let me say that I had pulled the yoke off with a gear puller.  It was extremely tight and I had to use the impact wrench to pull it off.)  It was extremely snug going back on and wouldn't go down far enough to get the nut started, so I tapped on it with a hammer using a wood block.  I have a feeling this was NOT something I should have done, because now the pinion gear is loose and clunky feeling in the carrier. I pull up on it and it feels fine.
Should the yoke be an extremely tight fit on the pinion gear?
Did I mess something up?
Can I go ahead and tighten it down or do I need to pull it back apart?
If so, then what do I do?
If not, what is the torque spec. on the pinion gear.

Thanks, in advance.

[quagmire]

The crush sleeve gets crushed when you tighten the pinion nut down to establish a preload on the bearings.  If you havent tightened it down yet, I wouldnt worry about it being loose.  Because the sleeve has been crushed before, there will be a lot of play in it until it is retightened.  Whatever you do, do NOT use an impact wrench.  The impacting action will brinell and damage the bearings.  There is no torque spec on the nut directly, it is determined by the turning torque of the pinion yoke.  Did you measure the turning torque before you disassembled it?  I'm not sure what the exact spec is for that, but you need to tighten it and measure the turning torque until it is correct.  If you didnt measure it before hand, the service manual will have a turning torque spec for both the pinion and the diff.  Assuming you didnt mess with the diff, add the two specs together to figure out the total turning torque you should see when you measure it.  Go slowly, and tighten it in small increments measuring in between, if you go too far the crush sleeve will need to be replaced.  Then you'll have to set it all up again.  You'll need a beam type torque wrench capable of reading inch pounds to do this correctly.  Oh yeah, the turning torque will be different for new and used bearings, and make sure the axles aren't installed when you measure the turning torque. 

[crcarch]

Then that it's normal for the yoke to be an extremely tight fit on the pinion gear?

Does anybody have the turning torque specs for the pinion yoke and differential that Quagmire mentions?  I'm afraid my old Motor manual and Chilton's are not quite up to that level of detail.

[quagmire]

According to the instructions I got with my ring and pinion gears, the pinion gear should have a turning torque of 20-25 inch pounds for new bearings, and 10-15 for used.  Note, this is for the pinion gear alone.  The instructions do not say the turning torque for the diff. They use the backlash method instead, which would require you to disassemble the differential first to get the proper readings for the pinion gear. I'm not sure where my service manual is hiding, but if and when I find it I'll post those diff specs for you. And yes, the pinion yoke will be a tight fit.  I put a little bit of antisieze on the splines of mine to prevent any galling. 

[tactransman]

 

[Chryco Psycho]

there si no crush sleeve in a 742 carrier
 the yolk will be a tight fit & anti sieze is a good idea but you are past that , you could have marked the pinion & nut & retightened the nut to the same position but too late for that too

[crcarch]

It's a 489 carrier, if that makes a difference.  I just want to make sure that I haven't damaged anything internally by hitting the yoke and getting the pinion "loose", which it wasn't before.

[quagmire]

I can't find a spec for the diff turning torque, so you have two options. First, you can pull the diff down, set up the pinion preload, and then set the diff up by using the backlash method. Or two, you can fab an adapter or something to fit in the side of the diff to measure the torque.  Take that reading plus the spec for the pinion gear and add them together to get the turning torque measurement for the whole diff.  Ideally, you'd measure this before disassembly. That way all you have to do is retighten it back to the original measurement.  If you end up having to uninstall the diff, you will have to recheck the gear pattern to insure both the diff bearing preload and backlash are correct.  If you go that route, you'll need to simulate a load on it by using a prybar between the case and the differential.  Otherwise you won't get an accurate pattern.