Open differential to posi

So I want to do a posi trac rear and I have an open diff. I’m not sure if I have an 8.5 or 8.6 and I’m not sure where to look. I also want to put 3.73 or 4.10 in it. Can I use my factory housing, or is there clearance/space or any other issue that I’d run into? I’m not opposed to grabbing an entire unit from a junkyard, but if I don’t have to I’d rather just use what I have. 04 Tahoe 2wd. Currently have 3.42 gears.

So you generally have to replace 2 things:

1. The ring and pinion to the ratio you want
2. The differential carrier. Depending on that you want, "some" aftermarket lockers can get dropped into the factory open carrier (those are called "lunchbox" lockers because that's what they look like.

Detroit, True-Trac and Auburn are the popular options out there. Look up what you have to replace on their websites.

You technically have the 8.6 (although I think most also fit the 8.5 because those are almost identical.) As far as junkyard swaps, you'll need to find a similar SUV with the G80, which was the factory locker made by Eaton, in the ratio you want. Not the strongest, but perfectly fine for just having a bit more traction when needed. Maybe find one from a Suburban because I believe those all came with 3.73s in this generation. Swap the entire rear end. Needs to be from an SUV, as the trucks used leaf springs.

Deadbaffy said:

want a posi trac rear, have an open diff. not sure if I have an 8.5" or 8.6", not sure where to look.
also want to put 3.73 or 4.10 in it. Can I use my factory housing, or is there clearance/space or any other issue that I’d run into?
not opposed to grabbing an entire unit from a junkyard, but if I don’t have to I’d rather just use what I have. 04 Tahoe 2wd. Currently have 3.42.

Click to expand...

If you don't care about throttle response, 3.73 will be fine.
I've 3.73, and every time I floor it, I die a lil inside. I strongly suggest 4.10.

If you're looking for entire axles, Suburbans, Yukons XL are more likely to have 3.73,
somewhat less likely to have 4.10. Tahoes tend to have 3.23 3.42 or 3.73.

If you have or have access to ring & pinion installation abilities
(complicated, time consuming, not difficult), pickup trucks are more likely to have 4.10.
Pickup trucks also tend to have bigger axles, so be sure to check for 10 bolts on the axle housing.

If you have or have access to fabrication / welding skills,
you can have your spring perches transplanted onto a pickup truck axle with little difficulty.

Thank yall!

Marky Dissod said:

If you don't care about throttle response, 3.73 will be fine.
I've 3.73, and every time I floor it, I die a lil inside. I strongly suggest 4.10.

If you're looking for entire axles, Suburbans, Yukons XL are more likely to have 3.73,
somewhat less likely to have 4.10. Tahoes tend to have 3.23 3.42 or 3.73.

If you have or have access to ring & pinion installation abilities
(complicated, time consuming, not difficult), pickup trucks are more likely to have 4.10.
Pickup trucks also tend to have bigger axles, so be sure to check for 10 bolts on the axle housing.

If you have or have access to fabrication / welding skills,
you can have your spring perches transplanted onto a pickup truck axle with little difficulty.

Click to expand...

Are you running some ridiculous size tire? I run 3.73's in my 2013 with 20" wheels 32" tires and my 2010 with 22" wheels and 33" tires and both of them will burn the tires off with no hesitation.

buckwild27 said:

Are you running some ridiculous size tire? I run 3.73 in my 2013 with ... 32" tires, and my 2010 with ... 33" tires
and both of them will burn the tires off with no hesitation.

Click to expand...

The ability to burn the tires off does not necessarily correlate with acceleration.
0-60MpH in over 8 secs disappoints; I'm used to Caprice 9C1 with 3.73 acceleration.
4.10 will help, with very little MpG penalty, considering how I drive.

I get that most people don't drive like I do - but those people might be surprised
to find themselves even more light-footed than with less gear, not to mention
that the MpG penalty will be minimal for them as well.

Marky Dissod said:

The ability to burn the tires off does not necessarily correlate with acceleration.
0-60MpH in over 8 secs disappoints; I'm used to Caprice 9C1 with 3.73 acceleration.
4.10 will help, with very little MpG penalty, considering how I drive.

I get that most people don't drive like I do - but those people might be surprised
to find themselves even more light-footed than with less gear, not to mention
that the MpG penalty will be minimal for them as well.

Click to expand...

My zero to 60 was roughly 6 seconds on my 13.
The 2010 is excluded it puts out 800hp and doesn't @##! around getting to 60mph.

OP, you should watch a few videos about the various differential mechanisms out there. Not really sure what you are trying to do with your truck. Here's probably the best video I've found that explains the differences between the major brands out there:

buckwild27 said:

My zero to 60 was roughly 6 seconds on my 13.

Click to expand...

You've a 6L80E, with what axle?. If I had a 6L80E, I'd be good with 3.73, or 4.10 if it were a tow horse.
But my '02 has a 4L60E with 3.73. I know it was never meant to be quick, but 4.10 would be a far better improvement on the compromise between miles per gallon vs Smiles per gallon, plus I'd gain the 4L60E some durability / longevity.

Marky Dissod said:

You've a 6L80E, with what axle?. If I had a 6L80E, I'd be good with 3.73, or 4.10 if it were a tow horse.
But my '02 has a 4L60E with 3.73. I know it was never meant to be quick, but 4.10 would be a far better improvement on the compromise between miles per gallon vs Smiles per gallon, plus I'd gain the 4L60E some durability / longevity.

Click to expand...

I have the 9.5 with G80