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8.25 gear swap setup
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Author:  Craig [ Sun Jun 15, 2003 9:44 pm ]
Post subject:  8.25 gear swap setup
I'm changing gears in a 8.25 rear axle in my 87 D150 Slant 6 truck.
Is there a secret to getting the rear pinion bearing off the pinion shaft without destroying it? :? Or can I use the old bearing cone to check the gear pattern? I'm thinking ahead... If I need to change the shim thickness under the bearing it will get expensive if I have to buy a new bearing cone for each shim trial.
Will I even need a different shim thickness? I took a used gear set and carrier out of a 1980 axle and will be putting it in my 1987 axle.
Thanks for any tips or secrets you can share.
Author:  bud L. [ Tue Jun 17, 2003 4:44 pm ]
Post subject:  yup
buy two pinion brgs, Timken preferred. Take one cone in to a good machine shop with a good pin-hone, and have them hone it for absolute minimal clearance, like a coupla ten thousandths. Use that one for trial fitting, and getting your pinion depth right. Then pull it back off and use the real one. Save the trial one for future use.
Author:  james longhurst [ Tue Jun 17, 2003 8:03 pm ]
Post subject: 
good call bud. you will never press that old bearing off in a slavageable condition. the hone idea is good, but i have achieved similar results with a die grinder and a flapper wheel for much less than a trip to a machine shop.
as for the shims, remember that chrysler usually planted the shims under the pinion bearing race in the diff housing. i think the preferred method is to replace the bearing races anyway and just pitch these shims and place new ones under the pinion bearing itself.

-james
Author:  Craig [ Tue Jun 17, 2003 10:08 pm ]
Post subject: 
The hone idea was on my mind. I was going to try this with the old bearing first to see how it worked out.
Author:  bud L. [ Tue Jun 17, 2003 11:06 pm ]
Post subject:  ?
It's pretty tough to get a straight, round bore doing it by hand. You'll tend to get an hour glass shaped bore, if you use , say a brake cylinder hone. But everybody has their own budget to help them decide what kind of a job you can live with. I used to do a lot of gear setups, and so I figured it was the price of a proper tool. It only cost about $25 for the machine work.
Author:  Doctor Dodge [ Wed Jun 18, 2003 1:19 am ]
Post subject:  Re: Mock-up bearing...
Quote:
It's pretty tough to get a straight, round bore doing it by hand. You'll tend to get an hour glass shaped bore, if you use , say a brake cylinder hone. But everybody has their own budget to help them decide what kind of a job you can live with. I used to do a lot of gear setups, and so I figured it was the price of a proper tool. It only cost about $25 for the machine work.
The "trial fit" bearing I have was honed-out for $20.00, that was $20 well spent, I have used this bearing many times over the years,
At the time I had it honed, I thought I had wasted 20 bucks on a special tool I would only use once or twice. :roll:
Oh, the one I have is for the 8 3/4 - #742 carrier.
DD
Author:  Craig [ Thu Jun 19, 2003 11:01 pm ]
Post subject:  How get u-bolts loose?
I borrowed a "flap wheel" and die grinder from a place I used to work at.
It opened up the bore of the old bearings just fine.
Then I discovered a problem with the existing axle in the truck.... the carrier bearing bores for the cups in the axle housing were machined slightly oversize at the factory allowing the bearing cup to freely spin in the housing with the cap torqued down. Is this a problem? I think so. The bearing cups have worn into the threaded adjuster plugs too. The truck has over 150k on it but I wanted different gears to help the Slant 6 move it. Had I left well enough alone it may have ran another 100k, oh well. Now I'm cleaning up the rusty doner axle I took the gears (3.55) out of so I can put them back in, then do a axle swap.
Next question.... Are the u-bolts (that hold spring, axle, shock plate together) made of any special heat treated steel? Here in Minnesota the nuts get permantly rusted on. I can't find matching replacement u-bolts just yet. Chryco dealer wants $18 each!!! for new ones. Next step is try heating the nuts and see if they come loose. Otherwise they get the cutting torch and I'll have to find new u-bolts.
Author:  Pierre [ Thu Jun 19, 2003 11:29 pm ]
Post subject: 
http://store.summitracing.com/product.a ... htype=ecat

I think those are the 3" u-bolts you need for the 8.25" on up axle. Yes they aren't cheap, but that kit is $50 for all 4 with nuts included. I took off stuck U-bolts from my parts car and it was a pain, had to use a long pipe to bust them loose. Unfortunately the threads came out stripped. I was trying to save the original u-bolts because at that time I didn't know you can buy them with the bottom of the U flattend, but I was wrong. I could chase the threads with a die, but I think I would rather just fork out the $ for new ones.

I know dealer stuff is expensive but I wouldn't think $18/ubolt seeing as how they used them on the dakotas.
Author:  Craig [ Fri Jun 20, 2003 8:37 am ]
Post subject: 
The truck uses SQUARE u-bolts, not U shaped ones.
Author:  Pierre [ Fri Jun 20, 2003 8:57 am ]
Post subject: 
Really, huh, go figure, I could have swore I thought someone told me to go to the dealer and ask for dakota 8.25" U-bolts.... And the ones I saw on a 80's dog van in the JY were round just like ours.
Author:  87Slant_sickness [ Fri Jun 20, 2003 12:25 pm ]
Post subject: 
mine on my 87 D150 are also "U" shaped, i just swapped out my 8.25 for a 8.75 with 3.91 SG in it out of a 71 D100, i bought custom axles awhile back that were made for my bolt pattern so i just swapped everything in.

Justin
Author:  Doc [ Fri Jun 20, 2003 12:40 pm ]
Post subject:  Re: How get u-bolts loose?
Quote:
I discovered a problem with the existing axle in the truck.... the carrier bearing bores for the cups in the axle housing were machined slightly oversize at the factory allowing the bearing cup to freely spin in the housing with the cap torqued .
You can take the caps to a engine machine shop and have them face a little off the cap ends. They will have a machine to do this. ( the machine is used to face con rod and main caps prior to re-sizing.)
You can use plasti-gage to figure out how much to "kiss-off" the ends of the caps.
DD
Author:  Craig [ Sat Jun 21, 2003 9:48 pm ]
Post subject:  Re: How get u-bolts loose?
Quote:
Quote:
I discovered a problem with the existing axle in the truck.... the carrier bearing bores for the cups in the axle housing were machined slightly oversize at the factory allowing the bearing cup to freely spin in the housing with the cap torqued .
You can take the caps to a engine machine shop and have them face a little off the cap ends. They will have a machine to do this. ( the machine is used to face con rod and main caps prior to re-sizing.)
You can use plasti-gage to figure out how much to "kiss-off" the ends of the caps.
DD
Wouldn't this make the bores slightly out of round? I'm guessing .002 or .003 off the caps would be plenty.
Anyway, I already removed that axle from the truck and am putting my doner axle back together. After taking the existing axle out of the truck I found serious rust under the shock plate that ate half way through the axle tube!! Time to move to someplace where vehicles don't get so rusty.
Author:  Doctor Dodge [ Sat Jun 21, 2003 11:11 pm ]
Post subject: 
You want to measure and just take enough off to keep the race from spinning. Your .002 - .003 is about right but don't get carried away.
DD
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