View Full Version : tranny problems

06-03-2004, 12:59 AM
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.


06-03-2004, 09:27 PM
well i know a lil about torque converters, and they arent comtrolled by the computer, the shift points are. if you have a bigger stall converter, you will feel it slipping until it reaches that stall height, for instance if you put in a 3k stall converter and you want to drive it on the street, your trans will feel as if it is slipping untily ou get to 3k rpms. it basically is putting more space in between the turbine and the pump inside your TC. on stock converters there is a minor stall, like 1200 to 1400 RPMs and there might be minor slipage there, or maybe ur TC is f'ed up.

and by drilling out holes it doesnt have to go through check balls, and slow down, and when there is high line pressure it will shift harder.

if ur TC is older it might just be getting tired after a few years, but soem slippage will occur at low RPM,a nd now with the "shift kit" drilling out those holes, it is working a lil harder, and maybe it was a problem before and just didnt know it due to the softer shifts

just a few suggestions, hope i could help

Jim Cook
06-04-2004, 04:00 AM
On 4R70W transmissions, Torque Converter lock-up is controlled by the Computer and the TCC solenoid in the valve body.

06-04-2004, 12:30 PM
sorry bout that then, my thinking must have been off a lil, dont know too much abot the 4r70-w, know basic stuff, and know a lil bit more about the hydramatics.

well if Jim cook says the torque converter solonoid then try pricing one of them out

06-09-2004, 03:45 AM
I have also noticed that when the engine is cold it shifts pretty good into reverse and taking off from drive. After it is warm, if I shift into reverse and hold down the brake and raise the rpm's to 1k I can feel the tranny "engage". Same thing with 1st. What could this be? Oh yeah... when I floor it from around 25mph it will shift into 1st but you can hardly feel it and after a couple seconds it will start to pull like it should. Does anyone have any ideas? One person I talked to said maybe the 1-2 accumulator piston or retainer may be installed up-side-down but I dont know, my buddy did it for me. I am open to all suggestions. I will be ordering a chip July 1st but I am also driving from coast to coast that month so I need to get this solved. All advice is greatly appreciated.