Hello! I’ve spent weeks and weeks searching for an answer to no avail so I figured I would post here as well.

I’m looking for a place where I can buy something like the 4t65e conversion kit sold on zzperformance (Gear Ratio Conversion Kit). Trying to get a 3.69 ratio for better low speed acceleration. Their one has been out of stock forever and I can’t find anyone else selling something similar and in stock aside from MMS who sells one for $2000.
Ideas? Car is a modded 2004 LeSabre with the following:

105lb valve springs
Steel Valve Spring Retainers
Custom pushrods
GT1 Camshafts
H-Body Downpipe w/ MagnaFlow Turbo XL muffler
Rollermaster Double Chain Timing Set
LS7 Hydraulic Roller Lifters
Extra thick front cover gasket
Machined oil pump cover
K&N drop in air filter
High flow fuel filter
Custom tuned PCM
180 degree thermostat

Right now 0-55ish is all 1st gear and then when it shifts to 2nd I’m getting a huge rpm/torque drop because all the gears are so long.

Any recommendations would be greatly appreciated!!

I believe you are running a 2.86 if I recall?? Which is pretty tall for a setup like yours.

3.05 and 3.29 are your compatible FD'*(someone correct me on this)

The 2 Bonneville'* I owned had the 3.06 and was pretty peppy off the line even with the L36 engine.

If you do find one, go LSD. One wheel wonders with these FWD cars will surely kill a FD. Don't ask me how I know.

Also, you will need to reprogram the PCM for the shorter FD, otherwise it will shift the trans too early or too late depending on which way it goes.

What Mike said ^^^^^^^

. . . and: Keep in mind that this increases torque to the clutches etc. in the transmission. If the transmission is already getting tired, this might finish it off. If not then not as big of a concern.

I found that MMS has a 3.91 version as well. While you're there, maybe you want to go a bit lower?

To answer the original question, I can't find any other sources. Maybe a strategic choice at a salvage yard would be the other option.