I have a 97 mark viii and it has the 4r70w tranny. I recently did the jmod and am having some problems afterwards.
1. When at wot it shifts early. It used to shift at 6k rpm but now its at about 5.2k in first gear only. 2nd and 3rd are good.
2. The torque converter doesnt lock up right away when taking off in 1st or reverse. You can hear the rpm's rise a little then it slams and takes off. If I keep my left foot on the brake just a little bit it takes off normally. While cruising on the interstate if I tap the brakes the rpm's will raise a little telling me the TC is working properly.
If your not familiar with it, the jmod is a simple procedure that makes the tranny shift faster and harder. I replaced the old style 1-2 accumulator spring and piston and left the bottom spring out like the instructions said to do. I also changed to mercon v fluid and put in new 2-3 accum parts. Drilling out certain holes in the seperator plate allows more fluid to pass through and shift "better".
If you have any suggestion on what may be causing these problems it is greatly appreciated. I was under the impression the tc lockup and shift points were controled by the computer.
Thanks,
Gino
1. When at wot it shifts early. It used to shift at 6k rpm but now its at about 5.2k in first gear only. 2nd and 3rd are good.
2. The torque converter doesnt lock up right away when taking off in 1st or reverse. You can hear the rpm's rise a little then it slams and takes off. If I keep my left foot on the brake just a little bit it takes off normally. While cruising on the interstate if I tap the brakes the rpm's will raise a little telling me the TC is working properly.
If your not familiar with it, the jmod is a simple procedure that makes the tranny shift faster and harder. I replaced the old style 1-2 accumulator spring and piston and left the bottom spring out like the instructions said to do. I also changed to mercon v fluid and put in new 2-3 accum parts. Drilling out certain holes in the seperator plate allows more fluid to pass through and shift "better".
If you have any suggestion on what may be causing these problems it is greatly appreciated. I was under the impression the tc lockup and shift points were controled by the computer.
Thanks,
Gino