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27 to 29 spline shaft on an 8.25

Pz10420

NAXJA Forum User
Location
Colorado Springs
I just got a 27 spline 8.25 with 4.10's in it. I also have a 8.25 with 29 splines and 3.55's. What does it take to swap the shafts? Do the gears have to be set again? Thanks in advance
 
you have to reset the gears, but it's far easier than a full gear setup, because the pinion depth is already set correctly for that gearset and housing. So all you need to do is get the carrier bearing preload and gear backlash set correctly and you are good to go.

Backlash should be the same as it was before (run a gear pattern before and after the carrier swap, adjust till patterns match) and carrier bearing preload should be within spec, might as well install new carrier bearings while you are at it.
 
you have to reset the gears, but it's far easier than a full gear setup, because the pinion depth is already set correctly for that gearset and housing. So all you need to do is get the carrier bearing preload and gear backlash set correctly and you are good to go.

Backlash should be the same as it was before (run a gear pattern before and after the carrier swap, adjust till patterns match) and carrier bearing preload should be within spec, might as well install new carrier bearings while you are at it.

Thank you Ken for giving good solid advice.

Yes you will have to swap the carrier/side/spiders. You will need to mount your ring gear on the 29 spline carrier. You need to note the BL before removing the carrier to be changed out.

You will need the following to reset the BL with the 29 spline carrier; Adjuster/spanner wrench for the 8.25 side adjusters, dial indicator with magnetic base.

For a guy like me that sets up diffs this is a easy job but it can be done by a DIY'er you just need some basic knowledge and tools.

When you tighten the adjusters, tighten the pass side last as that will move the RG away from the pinion and give you a good number. It may take several attempts at getting the BL right. Also you cannot put too much pre-load on the carrier bearings but you can put too little pre-load on them so make sure you get them tight. Set the locks so that they will hold the adjusters in the tight position.

I made my own adjuster wrenches with two large nuts(can't remember the size, maybe 32mm or 36mm), two 3' pieces or 3/4" black pipe, and two 1/2"-1/2" short extensions. Weld the nuts to one end of the pipe and the extensions to the other. This will allow you to leave a wrench in each end of the housing and step the RG into the proper BL

Make sure you mark your caps per side and keep bearing races with the proper side as well.
 
Thanks for the great info guys. I am a machinist so i have plenty of experience with indicators. Just recently got myself a welder so it sounds like this may be a great 1st project for me to attempt. Is the carrier that i have going to work with the gears that i will be putting on em? I thouhght I read somewhere that the carrier would only be good up to 3.73's or something like that?
 
Thanks for the great info guys. I am a machinist so i have plenty of experience with indicators. Just recently got myself a welder so it sounds like this may be a great 1st project for me to attempt. Is the carrier that i have going to work with the gears that i will be putting on em? I thouhght I read somewhere that the carrier would only be good up to 3.73's or something like that?

Your good to go, there is no "carrier break" on the 8.25
 
Yeah, its just a matter of pulling the old carrier out, swapping the ring gears and sticking back in the housing. Setting the backlash is wicked easy with the slide adjusters. I did it in my 94, took about a day to figure it out having never done gears.

Your good to go, there is no "carrier break" on the 8.25
Not true, there is but it has no relevance for our use of the axle. It's from 2.56+, our carrier

http://completeoffroad.com/c-94545-axle-id-information-chrysler-8-25.html
 
Just looking for a little more clarification before I totally pull it apart this weekend. My main concern is with the bearing preload. How do u set it and what is within spec? I'm pretty sure I understand the backlash being done with the side adjusters. Looks pretty simple. Do you have to rig up that tool with the 36 mm but on it. Cause just looking at it, it looks like you would be able to access the adjusters pretty easy with a screwdriver or punch and adjust them right next to the carrier. Also, I have measured the backlash and I am getting .011 but I have read that it should be between .006 and .010. So should I put it back to factory specs or back to where I found it? Thanks for the help
Pete
 
preload on the pinion bearing is set by putting an in/lb torque wrench on the pinion nut and tightening it till you get ~ 18 in'lb of drag as it rotates IIRC. look up the spec though as it's been 5+ years since I did mine. hopefully someone will chime in here with the specs. also for the side adjusters find a nut that fits in the hex in the center of the adjuster and weld it to a piece of pipe that will fit down the axle tube from the outside. That's what I did and it worked great. Ideally though I believe a spanner wrench should be able to catch the holes in the adjuster from within the cover opening, but I made due with what I had on hand.
 
Just looking for a little more clarification before I totally pull it apart this weekend. My main concern is with the bearing preload. How do u set it and what is within spec? I'm pretty sure I understand the backlash being done with the side adjusters. Looks pretty simple. Do you have to rig up that tool with the 36 mm but on it. Cause just looking at it, it looks like you would be able to access the adjusters pretty easy with a screwdriver or punch and adjust them right next to the carrier. Also, I have measured the backlash and I am getting .011 but I have read that it should be between .006 and .010. So should I put it back to factory specs or back to where I found it? Thanks for the help
Pete

I explained all of that in this post;

Thank you Ken for giving good solid advice.

Yes you will have to swap the carrier/side/spiders. You will need to mount your ring gear on the 29 spline carrier. You need to note the BL before removing the carrier to be changed out.

You will need the following to reset the BL with the 29 spline carrier; Adjuster/spanner wrench for the 8.25 side adjusters, dial indicator with magnetic base.

For a guy like me that sets up diffs this is a easy job but it can be done by a DIY'er you just need some basic knowledge and tools.

When you tighten the adjusters, tighten the pass side last as that will move the RG away from the pinion and give you a good number. It may take several attempts at getting the BL right. Also you cannot put too much pre-load on the carrier bearings but you can put too little pre-load on them so make sure you get them tight. Set the locks so that they will hold the adjusters in the tight position.

I made my own adjuster wrenches with two large nuts(can't remember the size, maybe 32mm or 36mm), two 3' pieces or 3/4" black pipe, and two 1/2"-1/2" short extensions. Weld the nuts to one end of the pipe and the extensions to the other. This will allow you to leave a wrench in each end of the housing and step the RG into the proper BL

Make sure you mark your caps per side and keep bearing races with the proper side as well.

do not try to adjust the cups with a screwdriver or chisel and i have yet to find a spanner wrench that fits in there like it should, i even tried to make one.

Set your BL back to what it is now or it will be noisy until it sets the new pattern in.

Since you are not removing the pinion, you do not need to worry about "pinion bearing pre-load" however, you do have to adjust the cups in tightly or you will not have enough carrier bearing pre-load. In my experience you really cant put too much carrier bearing pre-load on it. Just make them tight and if you really need a torque spec to go by I would set each side to 120ftlbs
 
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