3.29s into a 4T65-HD?

**Raysefanatic** · 03-13-2011

Hi all, tried to get some info via search, but the search engine disregards #s. So, if there are already threads (and I'm sure there's a few), I missed them, and I apologize.

I have a set of 3.29 gears out of a non-HD trans, was wondering if they'll go directly into my HD trans? Plug and play? Or is there a ton of stuff I'd need to change?

Looking for a bit more pop of the the line, but if it's more than just a "remove the diff cover, pull old gears, install new ones" situation, I'll probably pass on doing it.

Thanks in advance.

**TheOtherNick** · 03-13-2011

You have to remove the trans, remove side cover, remove 4th clutch hub, then remove chain and gears.

**Raysefanatic** · 03-13-2011

My fault for not describing correctly...

It's the diff, the planetary set and the side gears. Only the final drive is different, I think? Some say that this is weaker than the HD set, but looking at photos, they look the same to me. Maybe I'm wrong?

Anyway, other than tuning for the different final drive, is there anything else that needs to be done?

**Raysefanatic** · 03-13-2011

It would be this unit, only out of a non-HD trans:

http://www.grandprixforums.net/attac...s-100_0775.jpg

Sorry for the confusion.

**TheOtherNick** · 03-13-2011

That does not change the gear ratio.

**TheOtherNick** · 03-13-2011

That diff is just a little stronger, all you have to do to put that in is remove the diff cover, remove the diff and get a gtp passenger side axle.

**BillBoost37** · 03-14-2011

You'd need the diff, bearing, spacer, diff cover and a longer axle. You'd be compromising the strength.

Diffs are pretty cheap overall. But if you have an HD, the diff is already a 3.29. The change you would have to do to get the 3.29 ratio is to change the drive and driven sprockets from 37/33 tooth counts to 35/35 counts.

To do that, you'd basically be pulling the trans and doing a lot of work. It's much mroe than a diff swap in your case.

**Raysefanatic** · 03-14-2011

Originally Posted by BillBoost37

You'd need the diff, bearing, spacer, diff cover and a longer axle. You'd be compromising the strength.

Diffs are pretty cheap overall. But if you have an HD, the diff is already a 3.29. The change you would have to do to get the 3.29 ratio is to change the drive and driven sprockets from 37/33 tooth counts to 35/35 counts.

To do that, you'd basically be pulling the trans and doing a lot of work. It's much mroe than a diff swap in your case.

Thanks.

I do already have an HD, so, if it craps out than I'll change, but otherwise I'll leave it.