Swapped 8 3/4" pigs, now axles won't seat fully?

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MopaR&D

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I recently got loaned a 489 case center section with cone-type SG and 4.10:1 gears to swap in place of my 741 case with clutch-type SG and 2.94:1 gears. After installing the new 'pig' in the axle housing I went to slide in the axle shafts and they bottom out at least an inch before the bearings are seated! I can feel the splines engage in the diff housing and it goes another inch or so then stops. All the stuff online says these should interchange but it looks like the axle shafts need to be shorter am I missing something??
 
The cone type sure grip has a much larger pinion shaft block, instead of the sure grip thrust pin. I know that with the early tapered rears and the 1965 flange 8 3/4s, there were TWO pairs of possible axles. Non sure grip and cone type sure grip and then the clutch type sure grip. They both varied a little in length and were not interchangeable, because of the thrust block, thrust pin. Now whether that's true for the later 8 3/4s, I am not sure. If it's not, then it sounds like you may have a pair of early axles in a late model housing. I have had to trim axle ends off before with a miter saw to make them work. If you do that, you'll need to dress the edges of the splines so that they will slide into the side gears easily.
 
The cone type sure grip has a much larger pinion shaft block, instead of the sure grip thrust pin. I know that with the early tapered rears and the 1965 flange 8 3/4s, there were TWO pairs of possible axles. Non sure grip and cone type sure grip and then the clutch type sure grip. They both varied a little in length and were not interchangeable, because of the thrust block, thrust pin. Now whether that's true for the later 8 3/4s, I am not sure. If it's not, then it sounds like you may have a pair of early axles in a late model housing. I have had to trim axle ends off before with a miter saw to make them work. If you do that, you'll need to dress the edges of the splines so that they will slide into the side gears easily.

I was thinking of doing that but then they will be too short to work with my old diff. I just borrowed this 'new' case from FABO member 'nothingbutdarts' to see how my car would run with 4.10 gears as opposed to my 'airplane' 2.94 gears... I already know I need a larger u joint for the end of the drive shaft, that in itself may make the swap a no-go :(
 
Might be the split/side gears inside the sure grip are not aligned.

Put both axles in, have someone lever/crowbar one side to hold axle from turning and give the other side a quick jolt either direction. See if the axle seats in further.
 
It could also be the splines in the diff that is misaligned. This would happen if you turn one axle without having the other axle installed. Hook up the driveshaft, put the shifter in Park, install the axle as far as it will go and use a long prybar to turn the axle while pushing inward. The clutches in the Sure-Grip should slip enough to allow the splines to line up.
 
Might be the split/side gears inside the sure grip are not aligned.

Put both axles in, have someone lever/crowbar one side to hold axle from turning and give the other side a quick jolt either direction. See if the axle seats in further.

Bingo! This was my thought. Do you have stock tapered bearings or Green style axle bearings?
 
I have stock timken tapered rollers, I understand about the whole axle shaft endplay business... why?
 
I have stock timken tapered rollers, I understand about the whole axle shaft endplay business... why?

Why what?

If the bearings aren't seating, it is very possible as mentioned that the axles aren't engaging the second set of splines in the suregrip.

There are two sets of splines on each side of the suregrip and sometimes they become un-aligned and can cause issues like what you are experiencing. I usually line them up before installing the center section.
 
I have stock timken tapered rollers, I understand about the whole axle shaft endplay business... why?
Probably asking because with aftermarket axles and green bearings you have to remoce the spacer in the differential.
 
Probably asking because with aftermarket axles and green bearings you have to remoce the spacer in the differential.

Ok ya I was just wondering no attitude implied lol... I'm working with all factory stuff, I will try the trick with the splines tonight after work :thumleft:
 
Ok long delay but I finally figured out a way to get enough torque on the axle shafts to turn the clutches. Got it all back together and it RIPS... holy sh** I'm sure you guys know what it feels like to go from 2.94s to 4.10s. Only problem is the pinion seal is shot, will be replacing that soon...
 
okay so I just learned about the wonderful crush sleeve dilemma with replacing the pinion seal on the 489 cases. Now my question is, how many of you guys have gotten away with re using the old crush sleeve and just torquing the pinion nut back on?I would think as long as it's torqued to slightly less than the amount needed to crush the sleeve it should go back together with the same bearing preload
 
well that's good enough for me coming from you guys I'll take your word for it :)
 
If you can find a self locking pinion nut I would use one. There are chevy's that use the same thread. At the very least reuse yours, clean it and the pinion threads real good and use red Loctite on it.
 
Heck ya.crush sleeves are reusable.i do put them in a vise and tenderly try to compress or take out some of crush by spinning it around and pressing the center out to stretch it a little longer.then recrush it
 
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