Advise needed on broken posi

BC_Homegrown

Member
Sep 9, 2018
45
Powell River BC
For sure thanks Chevy we'll see how it goes haha. I'm envious of you guys that there are quality shops where you live dedicated to hotrods. And the prices for stuff are soo much better in the States. I live in the boonies up here cut off by water, just 2 general mechanic shops and everything is shipped in or out so pretty much have to do everything yourself or go broke.

On a positive note, found out a buddy's dad has the tools and setup bearings for a 10 bolt and will help me along if I end up having to change everything, turns out the local 4x4 crowd knows a thing or 2 about setting up rear ends.
 

SPG

Bumblebee Builder
Gold Member
Sep 1, 2018
1,458
Sacramento
For sure thanks Chevy we'll see how it goes haha. I'm envious of you guys that there are quality shops where you live dedicated to hotrods. And the prices for stuff are soo much better in the States. I live in the boonies up here cut off by water, just 2 general mechanic shops and everything is shipped in or out so pretty much have to do everything yourself or go broke.

On a positive note, found out a buddy's dad has the tools and setup bearings for a 10 bolt and will help me along if I end up having to change everything, turns out the local 4x4 crowd knows a thing or 2 about setting up rear ends.
Are you able to take a ferry to get to the main land for larger projects? I have a friend that lives in halfmoon bay that takes it every so often for those sort of things.
You would obviously need a truck or something.
 

biker

Veteran Member
Gold Member
Dec 7, 2014
5,297
Canada
For sure thanks Chevy we'll see how it goes haha. I'm envious of you guys that there are quality shops where you live dedicated to hotrods. And the prices for stuff are soo much better in the States. I live in the boonies up here cut off by water, just 2 general mechanic shops and everything is shipped in or out so pretty much have to do everything yourself or go broke.

On a positive note, found out a buddy's dad has the tools and setup bearings for a 10 bolt and will help me along if I end up having to change everything, turns out the local 4x4 crowd knows a thing or 2 about setting up rear ends.
Unless you are really confident and have the time, tools and space to do the job safely and accurately, a ring and pinion is one of those things you really should farm out to a pro. Parts are expensive, and it's really a "one shot" deal in that if you screw something up, it's not like you take it apart and make a few adjustments. Mistakes in most cases mean more new expensive parts.
And believe me, I am the first guy to tackle things that are over my head so I can learn something, so I'm not being a cautious prude and trying to discourage you.
Not knocking the 4x4 guys either, they probably do lots of these things, but ask some questions first, a guy with 38 inch mud tires probably isnt too concerned with rear end noise when he is installing a ring and pinion.
An experienced guy in a shop can bang out the job in a couple hours. Certainly not expensive for what you get.
 

hd_cat

Veteran Member
Sep 6, 2013
170
Cincinnati, Ohio
Hi all, I have a few broken teeth on the upper spider in a 8.5 posi unit in my 73. I was hoping to possibly get some suggestions on the best path forward from people with more experience as I've never done any diff work (taking the axles out was the furthest I've ever gotten) and the knowlege on this forum is incredible. Here is a picture of the carnage: View attachment 116811


The rest of the gears look in good shape. It is in a new to me 73 that apparently used to be drag raced with slicks. Its got richmond 3.73 gears, th350 and a 454, maybe around 400hp. Will be driven 90%street with a few test and tune days at the track with street tires. I would prefer doing the work myself but my mechanical skills are limited to google, youtube and learning stuff on here so I don't think I want to try to mess with setting backlash and the paint stuff(yet). I would just take it to a shop if I had to do that. Also I have a moderate budget but nothing crazy.

So based on that what is the best solution in your guys' opinion? Get the oem posi repaired professionally? Or is it possible to change just 1 spider gear without removing the whole unit? But then why did it break to begin with... or buy an open carrier and put a lunchbox locker in it? or bite the bullet and buy a full locker? Or close it back up and forget I saw anything :D

Any suggestions would be appreciated, thanks gents!


The best idea would be to replace the posi unit, gears, and axles with aftermarket, and to consider a C-clip eliminator kit for durability. The drag racing history has subjected those components to shock and wear. These upgrades would be expensive, but the improved reliability is worthwhile. The Broken spider gears may have caused damage to the bearings and other gears that is not readily visible. You could always bite the bullet and buy a Crate Differential from Strange or Currie, to the tune of $2500.00 or so. Would be cool to have a 12-Bolt!
IMG_1802.jpg
 

third_edition

Veteran Member
Lifetime Gold Member
Feb 7, 2004
103
Braeside, Ontario, Canada
Hi BC,

Just a few notes on rebuilding this type of rear end...

Setting the Pinion depth is a PIA as you have to continually press the bearing on and off as you "trial and error" fit it. Something I have discovered is that several companies make special bearings that are "slip" fit instead of "interference" fit for setting up the pinion depth. As long as you use the same make and pn of bearing for you final assembly, these are a great time saver (you could also take another new bearing and ream out the inside to make it into a slip fit).

I would suggest that you buy a new set of gears... if the car was drag raced and they are not the original gears, they could be too "soft" for the street (drag race gears are designed to "bend" under heavy load - not what you want for the street as they will wear out quickly). If they are the original gears, the damage to the spiders is probably indicative of the underlying damage to the R&P - you may be on the verge of breaking a tooth. Also, you can pick out a ratio that better suits your driving habits.

I understand that you are using shims as opposed to a "crush sleeve" for setting up the pinion preload - I have never gone this route, but if it turns out you decide to use a crush sleeve, buy several - they need to be changed each time you torque the pinion nut. Also, you will need a "big f..in bar" that you can attach to the pinion flange as you torque it (takes a lot of torque to crush the sleeve).

Good Luck :)
 

Cardinal

Veteran Member
Lifetime Gold Member
Jun 22, 2003
8,365
Endicott, NY
My opinion: buy a whole rear end off of somebody. It would be nice if a late model Tahoe/Suburban/Yukon rear was the right width!
 

BC_Homegrown

Member
Sep 9, 2018
45
Powell River BC
Thanks for all the tips guys, appreciate it very much, still in a holding pattern for the dial gauge. A new aftermarket rear end is unfortunately out of my budget, looked into getting a complete oem one from the wrecker but figured I might end up with the same problems with my luck . Don't really want to take it to Vancouver either that would add another 3 hundred bucks and a day off work haha, thought about it though.

Yeah the drag racing is a concern for sure, I'm not sure its history but it has a driveshaft loop, frame connectors and 3" studs so slicks were used at some point. Its currently a Richmond gear 3.73, looks pristine from what i can see but I managed to find some gear marking compound in town so I am going to see what the meshing looks like, will hopefully let me know the shape of teeth are in. And then backlash once I get the dial indicator. I will put up pics of the teeth pattern if I can.

I'll figure it out from there and see how she goes. Thats funny, my cousin said 2500 bucks like 10 seconds after I sent him a picture and I said no f'n way but it looks like he may be right.
 

procharged81

Veteran Member
Nov 16, 2011
139
NE PA
The best idea would be to replace the posi unit, gears, and axles with aftermarket, and to consider a C-clip eliminator kit for durability. The drag racing history has subjected those components to shock and wear. These upgrades would be expensive, but the improved reliability is worthwhile. The Broken spider gears may have caused damage to the bearings and other gears that is not readily visible. You could always bite the bullet and buy a Crate Differential from Strange or Currie, to the tune of $2500.00 or so. Would be cool to have a 12-Bolt! View attachment 117210

Or a 9”
 

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