Trouble installing rear axle shafts

[W-motorhead]

I need advice on how much force to apply when installing rear axle shafts. I replaced the pumpkin of my newly overhauled positraction differential (see "Rear Axle Master" thread) in my '63 Biscayne. The problem now is that the rear axle shafts are not seating fully, even though they engaged the spines of the diff. side gears during a test fitting outside of the vehicle. On a posi unit, there is a splined clutch plate retaining cup that must be aligned with the side gear splines on each side of the differential case. Do the axle shafts slide easily into place or do I need to whack them into place? So far, I have only given the axle hubs a few taps with a brass hammer. Do I need to bring a "BFH" into play here?
Dan Fults

 

[Don Jacks]

You may have to "convince" them with a little force ,Dan.Those gears are new,and will be tighter fitting to the axle shaft than the old ones were.

 

[Don Jacks]

Dan ,I went back to the video and noticed something.There are splines in both the "spider" gears,and the clutch cones that the side gears set in.These splines must line up or the axle wont seat properly! Once you get the axle started,rotate the axle shaft while pushing in in order to line up these splines.You'll likely have to do this on both sides.

 

[62impala409]

This exact issue was covered on the ChevyTalk forum recently. Something about starting the axle into the splines and then rotating the axle with a pry bar to to line up the rest of the splines in there. Need to do a search.

 

[Don Jacks]

You will most likely have to lock the pinion yoke[install the drive shaft and put the trans in gear],then rotate the axle with a large pry bar while pushing in on the axle.The "break away" torque on a 12 bolt was about 90 ft.lbs. With these parts being new,it's going to likely take some effort to get them to move.

 

[62impala409]

That sounds familiar Don. I have not found the exact post that I was looking for yet.

 

[W-motorhead]

I think the axle shafts are not going in fully because, as Don mentioned, there is misalignment of the internal splines of the side gear with those of the clutch plate retaining cup. Professor Kelly and I had these aligned when the differential was on his work bench, but maybe there was some slight slipping when I installed the pumpkin. Let me know what else you discover. I'll try the pry bar technique in the meantime.
Dan Fults

 

[skipxt4]

This is where, broken axle shafts come in handy. Install them through the splines, before tightening the posi housing bolts.

 

[DonSSDD]

http://www.chevytalk.org/fusionbb/s...00/post/2341547/hl/axle/fromsearch/1/#2341547 Read post here.

In this post, one side was in but it should give you an idea, Tom said what skipxt4 said. Search DZAUTO (Tom Parsons)on CT for anything rear end related for 55-64. He also bought one of the new Nitro posi and did pics of the inside.

Don

 

[62impala409]

That's the one Don. That info should get moving forward again.

 

[W-motorhead]

I solved my problem inserting the axle shafts into my newly rebuilt positraction differential by removing the pumpkin and realigning the inner splines of the side gear and side gear retaining cup (plate) on the work bench. I failed to accomplish this with the differential in the car using the method advised by Tom Parson on the "Chevy Talk" (see Don's posting above). The force needed to turn the axle was too great to get the necessary fine movements to align the splines. In fact, I bent several lug studs in the process! The attached photo shows the inner splines in the positraction that must be aligned. Once the splines are aligned, the axle shafts slide smoothly into place with only the resistance from the wheel bearing oil seals. When I replace my axle lugs and get back on the road, I'll make a final report to the group.
Dan Fults

 

[Phil Reed]

Old timers...you know, like Cecil and Dick..........cut the splined ends off a pair of axles and have assembly "tools" when they put the rear end together!!!!!!

 

[W-motorhead]

I noticed in a 1967 Chevy shop manual that in positraction differentials the side gear and side gear retaining cup were not separate, but rather integrated into a single part. Whether Chevrolet engineers made this change to save money or to lower the frustration levels of mechanics has been lost to history.

 

[models916]

Pretty sure the new Nitro diff for 55-64 is that way also.

 

[Don Jacks]

Chevrolet's "bean counters' didn't give a rip about the mechanics,especially once the car was out of warranty .The change in rear end design was a cost cutting measure.Remember that in 67 the warranty was extended to 60,000 miles due to pressure from Chrysler who went that way[5 years.60,000 mi.] in 64 0r 65.