Difficult to add a posi unit in my rearend?

big gear head

Veteran Member
Jul 30, 2001
There are so many thing wrong with that video. I guess if you are working on a piece of junk it would be all right to follow this, but if you are working on something that you want to do right then I recommend that you do not follow this video.


Bumblebee Builder
Gold Member
Sep 1, 2018
What does he do wrong? Genuine question, I have no idea.
You could argue that he shouldn't have reused some stuff and replaced the bearings. Should have used the right paint to see if there was any issues. and torqued the ring gear outside of the axle to get it more even. What he did was good general guidelines.

big gear head

Veteran Member
Jul 30, 2001
These are some of the things that were wrong in the video. Using used races on new bearings is a big no no. He didn't check the backlash BEFORE he removed the differential, which is why he had NO IDEA what to set it at when he reinstalled it. He also didn't do anything to hold the pinion PERFECTLY STILL when checking the backlash. If the pinion moves just the slightest bit then your backlash reading will be way off. He didn't get the bearing preload any where near tight enough when he put it back together. Don't mark the left bearing cap with a punch or stamp. There is no reason at all to mark both caps. Mark the right cap and that's all you need to do. DO NOT put punch marks on the left cap. That paint that he used to check the pattern was a complete waste. There was nothing readable in the pattern that he got.
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New Member
Jun 13, 2000
Churchville, MD, USA
So, I am a very handy guy and have restored several Camaros including engine work. I have never, however, done any real rear end work... How difficult is it to install a posi unit in my 71?
Several years ago (approx. 15) I installed a Powertrax Lock-Right locker in my 12 bolt. I believe they have them for a 10 bolt too. They work like a solid spool axle, but they automatically unlock during turns. Way easier then installing a posi unit and it worked. I'd check it out as an option. No special tools needed.


Veteran Member
Aug 14, 2020
if your car is not a "resto" car, buy a bolt in Ford 9 inch and be done with it forever..

Speedway and Quick Performance sells the "bolt in" housings....


Jan 10, 2005
Calgary, Alberta
As mentioned, it isn't hard per say, but you need to be sure to take your time, and do it right.
If you rush it, or skip steps, you're going to be shooting yourself in the foot.

There was a really good Haggerty video where a rear end was set up;
A superb idea was given , to grind out a sacrificial pinion bearing for the setup process, so that you only need to press on a bearing after the correct shim depth is found.

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