8 3/4 help

[Paul73]

Hello, I am currently in the process of setting the end play on my 8 3/4 in my 69 roadrunner. I took out the 3:55 that was in it and put in a 3:23 sure grip in it. My problem is the axles are super hard to turn by hand and i can’t get the axle back out on the passenger side. It was kinda hard to get in so I just tapped it with a hammer and wood block and I got the axle bolts snugged down good and was trying to set the end play but for some reason no matter how much I loosen the lock nut, I can’t the axle to wiggle in and out to set the end play. Sorry if this is a little confusing but I’m a young guy and I’ve never don’t this job before so any help or advice would be appreciated. Thank you

 

[RemCharger]

Tough question. Was the suregrip unit new or rebuilt? Maybe the splines aren't perfectly lined up.
Assuming the thrust buttons are good. What case #s were they. 742? 489?

 

[Paul73]

Tough question. Was the suregrip unit new or rebuilt? Maybe the splines aren't perfectly lined up.
Assuming the thrust buttons are good. What case #s were they. 742? 489?

I pulled it out of my 73 charger before I sold it and just thought I’d put it in because it’s a sure grip and I’m wanting to take it to test and tune at my local track just to have some fun with it. I did inspect it before I put it in and everything looked pretty good but no it was not rebuilt. It’s a 489 case.

 

[RemCharger]

Is it possible the Roadrunner came with the wrong axles

 

[Paul73]

Is it possible the Roadrunner came with the wrong axles

It might be possible but they are the ones that have been in the car and the number of splines is correct, the only thing I changed was the center section. Before I changed it, the axles would turn with ease. The old center section was an open diff though, would the sure grip make any sort of difference?

 

[RemCharger]

It might be possible but they are the ones that have been in the car and the number of splines is correct, the only thing I changed was the center section. Before I changed it, the axles would turn with ease. The old center section was an open diff though, would the sure grip make any sort of difference?

The axle length is same regardless of suregrip or not.
Try loosening the drivers side flange until you can feel a bit of slack

 

[RemCharger]

Did you check the splines on the axles carefully? Twisted/ scarred etc

 

[Fran Blacker]

To get the axle out put a rim on no tire on it. put lug nuts so they're loose and use rim as hammer hitting against lugs. Was the 8.75 you removed a clutch sure-grip? The 489 sure-grip were cone type. Put a cone SG in my open rear 66 Satellite and when axles bottomed out axle flanges were 3/8" from housing flanges. Put the cone SG and put a clutch SG in no problem. You maybe have the same issue.

 

[Paul73]

Did you check the splines on the axles carefully? Twisted/ scarred etc

Yes, they looked fine.

 

[Paul73]

To get the axle out put a rim on no tire on it. put lug nuts so they're loose and use rim as hammer hitting against lugs. Was the 8.75 you removed a clutch sure-grip? The 489 sure-grip were cone type. Put a cone SG in my open rear 66 Satellite and when axles bottomed out axle flanges were 3/8" from housing flanges. Put the cone SG and put a clutch SG in no problem. You maybe have the same issue.

It is a cone type but I will try that wheel trick and see what happens.

 

[Paul73]

maybe a set of green bearings would fix it since they don’t adjust… could the axle bearings cause this issue that I’m having?

 

[RemCharger]

If for some reason the splines are out of whack in the SG, you have to hold one wheel and spin the other to try to line them up. Not really easy.

 

[Lefty71]

maybe a set of green bearings would fix it since they don’t adjust… could the axle bearings cause this issue that I’m having?

I wouldn't even consider heading that direction until you know for sure what's going on with the lack of adjustability. I'd pull it apart and look carefully for issues as described above... also find a way to measure the spacers in the two differentials to be sure that isnt the problem. When you put it together, you should have had the adjustment side backed out, and gently adjusted to the desired side play (.018"?) until you got there.

Also, was the differential even free to turn before you put it in the housing??

 

[MoparLeo]

First clue was using a hammer.. If it doesn't slide in you stop.
If you don't know what you are doing, how do you know it looked good ?
Good to find someone to help you that is familiar with differentials and get a Service manual before you do any more work.