Axle Shaft Installation Difficulty - Help Sought

A few months ago I picked up a 3.7 pumpkin for my Sprite to replace the 4.2. I finally got around to installing it over the last couple of days, and everything went fine until I went to install the left side axle shaft. The right side slid fully into place with ease but the left would not go in without the persuasion of a BFH. Prior to fitting the pumpkin to the axle housing, I did a trial fit of the axles while I had the pumpkin on the bench and both axles slid into place without issue.

I'd like to know if anyone here can suggest what the issue may have been with getting the left axle to slide all the way in once on the car. Also, given the fact that I had to force the axle into place, am I to expect some sort of trouble with the diff once I put the car back on the road.

It may be possible that the axle housing is bent. I've never personally experienced this, but a very particular racecar builder/machinist friend insisted that bent axle housings were a major problem for Spridgets. He actually had a fixture built for checking and straightening axle housings. Unfortunately, he's retired now and sold off all of his equipment. I get concerned whenever a BFH is required to assemble anything!

The axles that came out to the old diff did so with ease and went in a couple of years ago with absolutely no effort.

No EFFORT that is the key to most anything. I do not know if the shaft is keyed and I am sure you tried rotating diff and shaft Question does it start but not go to seat of housing? Does it rotate after you beat it in? I worry you may have damage carrier bearings depending how hard you hit and the number of times. It is also not uncommon for one axle to be longer that the other . Madflyer

The axle is fully seated, the screws are in place and the wheels are tightened down. Everything rotates fine by hand and under engine power up on jack stands.

[FONT=Arial, Helvetica, sans-serif]I had both hubs off the car in order to install slightly longer wheel studs in order to accommodate 3/8" spacers. The bearings never came out of the hubs. I'm wondering if one or more of the new wheel studs on that side of the car took up a bit crooked going in, although I cannot imagine that being possible. The reason I am thinking (and hoping) it may be stud related, is because it was at the point when the axle flange first came into contact with the end of the studs, that the problem surfaced.[/FONT]

This morning I removed the wheel and inspected the studs. They are all parallel with one another and I see no signs of marring on any of the threads. Given that, I placed the flange of a spare axle facing backwards onto the threads and it went on with absolutely no friction. So, my theory about the axle getting hung up on misaligned threads does not hold water. The end of the axle shaft was obviously hitting an obstruction inside the diff.


Again the diff seems to be operating without issue. While turning the brake drum by hand the driveshaft turns and when I ran it thru the gears, both wheels turned (right side more than the left side) and there were no obvious problems and no noise or vibration of any type.


I am asking the question .... should I road test it?

Axle shaft should not require any force to install in the Axle although sometimes the last little bit requires a good push to slide over the last bit of the studs
Axle Splines fit into the 3.9 diff on the bench with no difficulty, Correct??
When inserting axle into diff with with new studs it is tight and requires a hammer to seat fully.
The only change was removing and reinstalling the hub with longer studs. Most likly something to do with the hub
Is the hub installed fully, that is completely square? Try removing the hub and see if the axle slides into the diff easily. If so there is an issue with the hub. With the hub off how does the axle fit on the hub?

Joe ... to answer your questions:

Axle Splines fit into the 3.9 diff on the bench with no difficulty, Correct?? I would not describe it as with "no" difficulty. Thinking back, one side inserted with total ease while the other side presented a bit more of a challenge. Unfortunately, I do not recall which side was more difficult but my money is on the left side.

Is the hub installed fully, that is completely square? I have to assume so, but that is only looking by eye. I have no way to actually measure it for squareness, but I do believe it is fully seated. Could the hub actually be installed without being perfectly square?

With the hub off how does the axle fit on the hub? I have not yet removed the hub and axle assembly.

Here's an update:

This morning I pulled the axle out, which was not as easy as one would normally expect it to be. I inspected the splines and they appeared to be in good condition. I tried to determine if the hub was rotating true by spinning it as fast as I could by hand. It appeared to run true, at least according to my eyes and without using any instruments. The bearing looked to be fully seated.

So I put a little bit of oil on the end of the spline of a spare axle and although it went in with a little more effort than normal, it went in easier than the other axle did a few days ago. I pulled it back out and after oiling the end of the permanent axle, I reinstalled it, again with a little more effort than one would expect, but with less effort than it took the other day. I thought this to be a positive sign in the right direction.

With the axle back in place, I rotated the drum and everything was working as it should. I then ran it thru the gears and still, no apparent issues. I then road tested it and all appears fine. No noises, whining or howling so I am going to leave well enough alone.

I want to thank all of you gents for chiming in with your opinions and suggestions. It was good hearing from everyone on what the perceived issue may have been and how to solve it.

By the way; I am loving this 3.7 gear as compared to the 4.2 which I removed. It has transformed the car.