Rear End Question

[67chevy1]

What is the difference in a 12 bolt pick up rear end and a car rear end? I'm wanting to take the open carrier out of my 67 swb and put in a posi unit but seems to me all I can find is car carriers and they say they won't fit. Thanks in advance guys!!!

[oklalawnboy]

Originally Posted by 67chevy1

What is the difference in a 12 bolt pick up rear end and a car rear end? I'm wanting to take the open carrier out of my 67 swb and put in a posi unit but seems to me all I can find is car carriers and they say they won't fit. Thanks in advance guys!!!

If I'm not mistaken, the pinion is smaller in a car rear end.

[Fitz]

Originally Posted by 67chevy1

What is the difference in a 12 bolt pick up rear end and a car rear end? I'm wanting to take the open carrier out of my 67 swb and put in a posi unit but seems to me all I can find is car carriers and they say they won't fit. Thanks in advance guys!!!

The truck diff is an 8.875T(12 bolt truck) differential as opposed to the 8.875P (12 bolt passenger car) differential. Here's a drawing of the housing for each, looking at the housing with the cover off.

Drive train specialists has the unit you are looking for.

[turp mcspray]

Truck rear has the smaller pinion. Trucks and cars have different ratio breaks for the 3 and 4 series. You will need a truck carrier.

[davepl]

If you look though my posts I listed the bearing combinations needed to make one work with the other (car posi carrier in truck rear end). I've never done it, but I found the information and shared it.

[hotrodder]

Is the carrier different for a 3:73 and a 3:08? I am wanting to switch, and was told I would need to get a different one. I have a 67 with a 12 bolt. Thanks

[67chevy1]

I'm pretty sure the carriers are the same no matter what gearing you have. I think there's just a difference in the housing between car and truck housings.

[hotrodder]

Thank you for the info. Hope this question was along the same lines as the original one.

[crakarjax]

Originally Posted by 67chevy1

I'm pretty sure the carriers are the same no matter what gearing you have. I think there's just a difference in the housing between car and truck housings.

Not so, there is a carrier break at which the carriers are specific to the gear ratio.

OP, if you want to go posi a TrueTrac will get you there and replaces the carrier entirely.

[67chevy1]

Originally Posted by crakarjax

Not so, there is a carrier break at which the carriers are specific to the gear ratio.

OP, if you want to go posi a TrueTrac will get you there and replaces the carrier entirely.

Ok that's exactly what I was looking for. Now for my next question I looked at summit for the true trac which one am I going to need? Is it the 8 5/8, 6"?

[crakarjax]

This is the one I got
Amazon.com: Detroit Locker 913A555 Trutrac...EDIT: I think I got the passenger car version on accident, so don't get that one!

Here's some general info

http://www.drivetrainshop.com/GM_12_Bolt_s/105.htm

The one for truck rearends:

Amazon.com: Detroit Locker 913A315 Trutrac...
Now, the website says this is only for 3.73 and up gears so if you want to run shorter gears (as I do -- 3.42) then you might be out of luck.

http://www.differentials.com/uncateg...-differentials

[hotrodder]

Thank you for the correct information about the carrier difference. I now have a 2:73 gear and am wanting to change to a 3:07 but changing the carrier takes more money than I can afford to spend right now.

[jhwkns]

Originally Posted by hotrodder

Thank you for the correct information about the carrier difference. I now have a 2:73 gear and am wanting to change to a 3:07 but changing the carrier takes more money than I can afford to spend right now.

Those use the same carrier as each other. I think the break is at .348

[dell72]

A truck carrier is longer ( wider) than a car carrier