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Best place to get the Jmod

KV007

where did you guys get your jmod from and price?

ReverendDexter

My understanding of the J-mod is that it's something you do yourself in your own driveway/garage instead of paying the money for an aftermarket shift-kit.

Abb0

If you're confidant regarding removing the valve body from the trans then I agree with the Rev. However, if you're not then I'd get someone to do it for you. If done wrong you could cause an awful lot of problems. There are a heap of springs and crap that can go everywhere if you're not careful.

I was having an issue with my trans and ended up needing the VB replaced and the transmission shop did the J-Mod and upgraded the internals for $600 all up.

KV007

i thought you had to buy a shift kit and that was the j-mod

MG2V

You can buy shift kits. The J-mod, however, is a procedure you do yourself that gives the same result as a shift kit. It's free outside tools and new ATF.

I did it on my VB last July, and love it. Below is an excellent video showing the procedure.

CalBoy101

I was trying to get up the energy to do the J mod myself but I have too many other things to do on the car stacked up so I took the lazy way out and ordered a valve body from Silverfox Transmissions, it has the J mod and other things done to it to improve shifting, at $275. its not too bad. Silverfox has a lot of experience with 4r70ws.

I haven't put it in yet but it looks pretty at least.

KV007

anyone else used this before? that isnt too expensive either

blownstang

You can have a shop do the Jmod if they know what it is/what they are doing.

BOSSMAN2888

The Baumann Engineering kit is a great kit with five different levels of performance to choose from on the 1-2 or 2-3 shift. The instructions were very detailed and well thought out kit. I installed it in 2010 and wish I would have done it in 2002. Best $115 I ever spent.

Tang Stang

The FULL tech article from Jerry: Drilling the separator plate is outlined on pages 13 & 14, which is what is typically referred to as the "Jmod" around here.

Addendum for 98+ 4R70W's:

MuscleCars

Noob question..... but what is the JMod???

Tang Stang

See the links directly above your post?

MuscleCars

So its something to firm up the shifts?

2000stallion

Jmod is nothing more than drilling some bigger holes in the separator plate of the valve body and removing a couple springs. I have a 4r70w valve body with the jmod done for sale.

termi_GT

How much?

MuscleCars

What I'm asking is, is that what it's for? Firmer shifts?

ReverendDexter

Read the article Tang linked, it will answer all your questions about it

KV007

So as i look into it, dont have room at my apt or time so im looking into just buying a shift kit and taking it to a shop here. How many hours do you think it would take and what do you reccomend

MG2V

Firmer and faster shifts, decreased temperatures, longer transmission life. I drilled the feed holes to the 650 HP level and removed the 2-3 accumulator spring. I can tell you, the difference is night and day.

The mod was designed by Jerry Wroblewski, one of the head engineers in charge of the 4r70w.

I had my VB dropped in a little over an hour. About 5 hours total considering draining the trans pan, removing and reinstalling the VB, refilling with ATF. That was in my garage laying on my back, so a shop should be able to do it a lot quicker.