Kylliss

So I have an automatic 99 Mustang GT, and I'm looking into getting a shift it for it. However I can't seem to find anything telling me what the difference is between different shift kits. I use americanmuscle.com usually to get mods for my car, and there are two kits, one is called a "B&M Shift Improver Kit - 4R70W" (this is made specifically for the 4R70W transmission I assume, which is what is in my Mustang) and the other is a "Performance Automatic Street/Strip Shift Kit" (this is said to be compatible with the transmission I have as well). I can't find anything relating the two, or anything talking about what would be the best shift kit for me to get. Money isn't that much of an issue, so if you have any suggestions on what kit would be better, or if you know of another kit that would better please let me know!

Urambo Tauro

Welcome!

The go-to "shift kit" for the 4R70W is the J-Mod. There's a wealth of info to be found over at TCCoA on how to do it.

As for comparisons, I really don't know much about other kits. However, my '96 Thunderbird's 4R70W did have a B&M kit in it when I bought it, and when I rebuilt the transmission I decided to perform the J-Mod. When I did, some of the holes in the separator plate had to be enlarged beyond the B&M spec.

If you can get a hold of the instructions for the other kits, you could compare drill bit sizes and such. Just make sure that before you do any drilling that you're honest about which power range you're modifying it for. You do NOT need 500HP-level shifts on a stock engine.

281Keeper

Did you by chance decide on a Kit to use? I ask because I would like to do same on my 02 Saleen

delling3

This is a nearly 4-year old post, and the original poster has not been back on the forum since 2017, so doubtful he will respond. That said, the "J-Mod" remains the preferred way to modify the 4R70W transmission.

281Keeper

Thank you! Could you please link me to a J Mod? I am under the assumption my 02 Saleen and a 02 GT have the same trans. I can find B&M shift kits but I want the best for my money. Any suggestions would be appreciated.

delling3

J-Mod is not a "shift kit" that you simply purchase and install in your transmission. It involves some fairly simply modifications to the existing valve body in the transmission. I think there are some companies that are packaging "kits" that include appropriate drill bit sizes, etc., but most everything you need is already in the transmission. Here is a video that details the process. . A lot of information in the forums or on the web (google J-Mod Transmission).

Hope this helps.