8.25 Centre and Sure Grip issues

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Pana.Mopar

Pana.Mopar

Duster Down Under
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Hi All,

I've got a couple of issues with the Chrysler 8.25 rear in my '76 Duster. I purchaed a Sure Grip Centre and 3.55 gear last year and a few weeks ago I went to Diff Shop to get them put in and got a call later that day that the Sure Grip is incorrect.. Basically there's way too much backlash when the crown and carrier are together the carrier is all the way over and there's too much backlash.. Has anyone else experienced this issue?? In the end, I went down to the Diff shop and I decided just to put the open centre back in with the 3.55's.. The diff is great but really want that Sure Grip in there...

The centre is exactly as the one in the photo and has the numbers: 18-05-039-903 stamped on the front of the carrier. Does anyone know what this is off??

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The guy at the machine shop said that it needs a 15mm shim to go between the crown gear and carrier so he can get the gears to mesh and adjust the backlash. Is this correct?

Any advice or help is greatly appreciated. I really want to get that Sure Grip in there...

Thanks in advance for your assistance...
 
There is a difference between carries for gears 2.45 and down compared to 2.45 up.
 
Pana, I'm having the exact same problem. I have decided that the SG unit is wrong. Its possible there was a difference in the carrier sizes, but it has nothing to do with 2.45s. Every unit I've seen offered for the dak was 2.56 and up. I've never heard of a dakota with 2.45 gears in it. The shortest I've heard of in a dak was MAYBE 3.23. NObody here seems to be able to offer any ideas as to why it won't work or what's going on. I'm going to try to find a different SG unit for my rearend.
 
Old post I know.

I just ran into the exact same issue with the 8.25 in my Jeep Cherokee.

Same center section, 3.55 gears, same results.

It is correct that the carrier breaks are 2.45 and down, 2.56 and up.

The carrier we have will not accept the 3.55 gears.

The troubles with using a spacer to lift the ring gear to the correct location are that
1) I dont think anyone makes the spacer, though a GM8.2 spacer can be modified to fit
2) You will need to find 3/8-24 LH thread x1" or x1 1/8" hardened ring gear bolts, which no one seems to make, or use the stock length bolts and live with fewer engaged threads
3) When the ring gear sits atop the spacer, it sits high enough that it no longer is engaged by the machined "center" of the posi unit, which makes centering the gear exactly on the carrier near impossible.

Just thought I would share my $.02 from going through this. Good luck!

Ken G.
 
Have either one of you call RANDYS Ring & Pinion the are in all the hot rod books. Just a ideal
 
If you jump on the Auburn Gear site it tells you on the 8.25 that a section of the diff has to be grind down so that the carrier can move and ring gear can engage and enough room for backlash adjustment...

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Pana.Mopar said:
If you jump on the Auburn Gear site it tells you on the 8.25 that a section of the diff has to be grind down so that the carrier can move and ring gear can engage and enough room for backlash adjustment...

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Click to expand...

did you try this grinding mod and did it work?
 
I will take a look at mine this weekend too.

Here is another thought....not necessarily a good one.

The ring gear flange on this posi unit is ~about~ .250" lower than the same flange on the non-posi carrier I have, which fit fine with 3.55 gears.

Even if we manage to get this posi unit to fit in the axle by grinding some clearance, it will need to have been shifted that approx. .250" towards the passenger side to get the proper backlash.

This will make the axleshafts shift the corresponding amount. I am not certain that this will be a good or desireable condition.
 
Looked at it again today and hand fit the carrier with bearings into the rear end housing, without the caps installed.

The carrier is at its max adjustment towards the passenger side, meaning that the passenger side bearing is bottomed out in its travel that direction, and the backlash is still way too large.

There is no interference with the diff housing and carrier. So the grinding mods in my case will not help.

only a ring gear spacer will help, and I havent found one for this application. The gear flange on this posi unit is .275" below the flange on the original non posi diff carrier.

good luck I am putting back in the non posi center.
 
I clearanced my housing like the picture showed, and it STILL wouldn't fit. I finally gave up and installed the open carrier so I could get my car back on the road. There is something different about them, for sure, although I still have mine. I don't think machining a spacer is going to work, because of the axle fitment issue above. If they're all the same, I can't figure out why this won't work, UNLESS its coming from an 8.25 front diff, in which case, there may be a different fitment for those. I had intended to try to install this in a Dakota 8.25 rear housing just to see if it would work, but haven't gotten around to it yet. I know that an open carrier out of a dakota 8.25 will fit our a body 8.25 just fine, because that's what I used.
 
I bought the same sg and had the same problem, so I put the 3;55 back onto the open carriers and will sell the sure grip. If you need to get the ring gear onto the carrier easily, heat it in oven 400 degrees for 30 minutes and put carrier in freezer for 30 minutes, the install ,it will drop right on , same with pinion bearing
 
Even if you did make a spacer no one sells 3/8-24 LH grade 8 bolts 1.00 long or longer. At least I cannot find anyone
 
yep, thats a 2:45 suregrip. i just went through this a few weeks ago. cost me almost 500 bucks for an auburn setup so i could get my diff out of the gear shop. good luck trying to sell a suregrip that only works with 2:45's. im using mine as a paperweight.
 
I'm not sure if this is the problem, but my dad and I tried to put a SG in a 93 Dakota once (bought the unit for a 69 Charger but the bearing were too big and didn't fit), and the one thing that was different between the Dakota open rear end and new SG was a tooth'ed ring for the anti-lock brakes. The original open unit had the ring and the new unit didn't. The ring looks like it sandwiched between the ring and carrier, so it might be that you just need to find an anti-lock brake ring. I think it was separate from the carrier itself, but we didn't bother trying to remove it. I don't think it was .25 thick, maybe about an 1/8" but you might look around and see if you can find some pictures of the anti-lock ring.
 
nope. the problem is mopar makes two suregrips for the 8 1/4. one for 2:45's , and one for 2:71's and up. and some of us buy them without knowing. heres mine. and heres a pic of my auburn suregrip that works with my 3:55s. notice the useless one on the floor behind it.

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