Jmod

I'm looking for those who have any experience with the Jmod or has any knowledge of it.

The more and more I read, the more I see people saying that increasing line pressure in the 4R70W is a risk, especially on higher-HP cars. A tune only really increases line pressure while something like the Jmod achieves its firmer shifts in other ways. Im more interested in the durability aspect of the Jmod (increased/faster fluid transfer, heat dissipation, and elimination of shift overlap and wear).

How does the Jmod perform under both part throttle and WOT?

How many actuator springs were removed? Stated per TCCoA articles, they call for all springs to be removed.

Any input is appreciated.

Thatsweetstang said:

I'm watching this thread. Been wondering how a jmod worked.

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This is what I've gathered. Other shift kits and handheld tuners affect the transmission shift patterns and firmness by increasing line pressure. Now, on "stockish" power levels (200-350rwhp), increasing line pressure is "acceptable". Once you start pushing serious power through the tranny (400/450+rwhp), messing with pressure can get you into trouble.

The Jmod doesn't mess with line pressure. With the Jmod, you affect transmission performance by eliminating actuator springs (I have no idea what this does exactly) and by drilling larger holes in the separator plate. The larger holes allow much quicker transfer of transmission fluid from one section of the tranny to the other, along with greatly increasing the amount of fluid transferred). This allows for much greater heat dissipation (heat is the #1 enemy of any transmission) and faster engagement of various tranny components (decreasing shift time, eliminating shift overlap, and decreasing a lot of wear/tear).

Basically, the Jmod was created/named after the chief Ford engineer of the 4R70W. He said that he, and his team of engineers, were limited in what they could do with the tranny by way of the Ford big-wigs who felt that a mainstream transmission like the 4R70W needed to be as "forgiving" (ie. as pussified) as could be. Therefor, certain steps were taken to essentially "weaken" the transmission. The Jmod is a step-by-step process to eliminate the fragile nature of the tranny and allow it to perform like it was intended.

sneaky98gt said:

I think I enlarged the holes to the 350-450 rwhp option, and left my stock springs in there. I absolutely love the way it shifts. It is still extremely smooth at part throttle, but will spin the tires every time on the 1-2 shift, even with the drag radials on. So if you're spinning the tires shifting, I personally don't see the point in a harder faster shift.

I think you can enlarge the holes to the 450+ option without much sacrifice in part throttle smoothness. It's changing the springs that really make it shift hard. Don't hold me to this, but I'm pretty sure that you, with an 02' 4R70W, already have the best spring setup there is. If you want any change in the shifting at all from the springs, you have to take them out. And if you take them out, part throttle will be very firm. I do know that.

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I was waiting for you to post lol. My MAIN concern is longevity, not so much the shift firmness. I hear that this relieves a lot of stress on the tranny

sneaky98gt said:

It is much better for the transmission. I'm extremely surprised that you hadn't already done it. My understanding is that enlarging the holes is what helps the longevity, and the accumulator springs are more for harder shifting.
Also be sure to do an oil cooler at the same time. I'm assuming you already have a built tranny and torque converter?

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Aside from the 3200 stall, my tranny is stock (I also put in a cooler when I put the stall in)

sethahoward said:

I did the jmod and i pulled the accumulator springs out. I should have left them in. part throttle shifts were too hard, I was going to put the springs back in but I ended up getting a deal on a t-56 swap so i went that route.

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This is what I've read Im leaving the springs in.