68-72 rear end issue

[Jd63]

I took the posi diff out of a 68 and put in a 72 rear end housing but now I have axles that have in and out play at the Center diff pin, did I do something wrong or does that swap not work since 68 has a narrower housing

[PowerdbyChevy79]

Originally Posted by Jd63

I took the posi diff out of a 68 and put in a 72 rear end housing but now I have axles that have in and out play at the Center diff pin, did I do something wrong or does that swap not work since 68 has a narrower housing

What Axles did you use?

[Jd63]

Hi I used the 72 axles. So our other 72 doesn’t have any movement against the axle and Center pin, now the 68 posi carrier that I put in the 72 housing with 72 axles works but it has about .140 thousand movement between the end of the axle and the Center pin on both sides, which isn’t right.
I was wondering if the the 68 has thinner spider gears causing this issue amd how can I fix it
Thanks JD63

[LNP]

Originally Posted by Jd63

Hi I used the 72 axles. So our other 72 doesn’t have any movement against the axle and Center pin, now the 68 posi carrier that I put in the 72 housing with 72 axles works but it has about .140 thousand movement between the end of the axle and the Center pin on both sides, which isn’t right.
I was wondering if the the 68 has thinner spider gears causing this issue amd how can I fix it
Thanks JD63

They make shims that go behind the spider gear. I would check the carrier you took out and check to see if they are thicker than the ones behind the 68 spider gears. As a norm they generally look like the pic below. This of course assuming the two axles are the same diameter so they fit the spider gears equally the same.

[Wrenchbender Ret]

Have you checked the fit of the drums yet. There are differences in the length of those 2 axles. I don't remember all of it but someone will pop in & explain it. Have you tried using the axles from the 68?

George

[Jd63]

No I haven’t, but that diff is narrower than my 72, so they wouldn’t work unless I went back to the 68 diff. The spider gear isn’t the problem its the axle moving in and out on the side gear because it’s not tight against the Center pin which is leading me to believe that the axle gears are not as deep as the 72s

[LNP]

Originally Posted by Jd63

No I haven’t, but that diff is narrower than my 72, so they wouldn’t work unless I went back to the 68 diff. The spider gear isn’t the problem its the axle moving in and out on the side gear because it’s not tight against the Center pin which is leading me to believe that the axle gears are not as deep as the 72s

Sorry I said spider and I should have said side gear. The C clip sets inside a groove in the side gear so if the side gear is not shimmed properly or in this case maybe shimmed different from the OE carrier it will allow the axle to move to much in and out. Changing the shims can/ will increase and decrease this movement. Take a dial indicator and measure the in & out play to see if its in spec or not. If I remember right axle end play should be 0.10" - 0.25" Also check the axle in the c clip roove to insure theres not any excessive wear check the c clips as well. Hope this helps and you figure it out.

[Jd63]

I’ll do some checking and post what I find

[Jd63]

Hi
I took a reading and it’s 40 thou play. I have pictures but can’t seem to load them.
So 72 housing. 72 5 bolt axles. 68 posi unit rebrg 40 thou play on axle to Center pin on both axles
Everything looked normal when cleaning diff up. All plates that were there were installed but it’s like it’s missing one one each side which would push the axle gears closer to the pin to eliminate the play, but that won’t work as then the spiders wouldn’t fit.
🤨
Thanks for everyone’s ideas so far
Jd63

[Myself]

So it seems like you're saying that if the c-clip groove in the axle was a little further outward then the axles would sit a bit further INward, against the pin, right?

[Wrenchbender Ret]

I think when you put the drums on the will stick out. I think there are special axles for this swap. Of coarse the 68 has 6 lugs & the 72 has 5.
I'm surprised someone more familiar with this has not popped in.

George

[raggedjim]

JD, if I understand you correctly you are using the 72 axles in the 72 rearend with a 68 center carrier. This should work fine, I have done it before.

When you did the change did you rebuild the clutch pack? If not it probably needs to be rebuilt. If you can rotate one tire by hand with the other against the ground it needs to be rebuilt.

[Jd63]

I did rebearing it and inspected all the clutch plates and they looked fine, there certainly wasn’t enough wear to take up the difference I need to. I’m afraid it will wear on the axle c clips being able to move in and out and effect handling

[raggedjim]

I'm thinking that as long as you install the pin and the c-clip is still trapped in the cup of the gear so it won't drop out you should be okay. BUT i'm not a rearend guy (well kinda...) but I have had axles out of lots of these trucks and there is usually some play.

[raggedjim]

40 thou is .040 not .40

If it is .040 I would run it, if it is .40 I would not.

[Jd63]

Thank You for clarifying my mistake that I made.
The axle play is .040 thou not .40
It seems like that would be to much movement on those c clips. Ultimately you would have your rear end axles able to move .080 thou on you

[LNP]

Originally Posted by Jd63

Thank You for clarifying my mistake that I made.
The axle play is .040 thou not .40
It seems like that would be to much movement on those c clips. Ultimately you would have your rear end axles able to move .080 thou on you

Food for thought, you could go with c-clip eliminators

[Jd63]

What kind of job is it to do the c clip eliminator kit, I haven’t had any experience with that

[LNP]

Originally Posted by Jd63

What kind of job is it to do the c clip eliminator kit, I haven’t had any experience with that

This video goes over doing it

https://www.youtube.com/watch?v=6-LaC7cs_FQ

[Wrenchbender Ret]

Classic Parts of America has conversion axles that would probably solve the problem.
$$$$$$.

George

[dmjlambert]

So 40 thou is thinner than a dime, is that what we're talking about here?