New tranny mods, strange drive behavior

Jett · **Joined:** Fri Apr 17, 2020 12:07 am **Posts:** 250

Got the Jeep on the road again after new suncoast and transgo shift kit. Drives great, not exactly quick firm shifts, but little better I guess. However when shifting into D there is significant delay and then it’s a bit harsh when it does lock in. This does not happen to reverse, and it doesn’t matter if it’s warm or cold. What could this be? I’ve only gone about 50mi on it but It’s not improving.

Jett · **Joined:** Fri Apr 17, 2020 12:07 am **Posts:** 250

It’s a solid two seconds to engage. Fluid level is good, however I’m trying to remember if it’s recommended to run these trans over full a little? I’m right around the hot mark when hot.

casm · **Joined:** Sun Jan 29, 2006 5:05 pm **Posts:** 694

Jett wrote:

It’s a solid two seconds to engage. Fluid level is good, however I’m trying to remember if it’s recommended to run these trans over full a little? I’m right around the hot mark when hot.

Yes, going a bit over-full is necessary. The hot level is still lower than it should be. Anywhere from a half-quart to quart may be necessary; add gradually and see what happens.

FWIW, I also have a Suncoast TC (no Transgo / Sonnax kit, however) and have no problems provided that the Jeep hasn't been parked for more than about three or four hours. After that, it's necessary to give it about 10-20 seconds of idle time (depending on how warm the transmission is) in Park in order for the transmission to build up pressure before driving. After that point, it shifts completely normally.

I really need to drop the transmission pan at some point and see if the spin-on filter is still fully in place; it's the return line filter and is responsible for keeping fluid in the torque converter with the engine off. Take a look at TSB 21-016-05 for details - if the filter that's currently in yours matches the suspect part number, that may be your answer.

Jett · **Joined:** Fri Apr 17, 2020 12:07 am **Posts:** 250

casm wrote:

Jett wrote:

It’s a solid two seconds to engage. Fluid level is good, however I’m trying to remember if it’s recommended to run these trans over full a little? I’m right around the hot mark when hot.

Yes, going a bit over-full is necessary. The hot level is still lower than it should be. Anywhere from a half-quart to quart may be necessary; add gradually and see what happens.

FWIW, I also have a Suncoast TC (no Transgo / Sonnax kit, however) and have no problems provided that the Jeep hasn't been parked for more than about three or four hours. After that, it's necessary to give it about 10-20 seconds of idle time (depending on how warm the transmission is) in Park in order for the transmission to build up pressure before driving. After that point, it shifts completely normally.

I really need to drop the transmission pan at some point and see if the spin-on filter is still fully in place; it's the return line filter and is responsible for keeping fluid in the torque converter with the engine off. Take a look at TSB 21-016-05 for details - if the filter that's currently in yours matches the suspect part number, that may be your answer.

Thanks I’ll try another quart. What’s interesting about this is that it’s all the time, so it’s not a TC drain back issue, I can drive for 5 miles and then reverse into a driveway to turn around and when I put in D again it will take a 2 count to notch in.

Jett · **Joined:** Fri Apr 17, 2020 12:07 am **Posts:** 250

Could this be because I omitted the resistor in the shift kit? The instructions didn’t even describe where to put it.

casm · **Joined:** Sun Jan 29, 2006 5:05 pm **Posts:** 694

Jett wrote:

What’s interesting about this is that it’s all the time, so it’s not a TC drain back issue, I can drive for 5 miles and then reverse into a driveway to turn around and when I put in D again it will take a 2 count to notch in.

How recently was the TC replaced and the Transgo kit installed? The TCM does take some time to relearn, so that may part of it.

After the Suncoast went into our KJ, it immediately went on a 1,300-mile highway trip while towing around 3,000lbs. Sorry, but I can't really tell you how long the relearn takes because it was almost entirely straight-line highway runs and the TC seemed to have bedded in by the time I got to where I was going.

Jett wrote:

Could this be because I omitted the resistor in the shift kit? The instructions didn’t even describe where to put it.

Nope, you're fine. All it does is make the 1-2 and 2-3 shifts firmer to the point of being eye-popping. Even Transgo recommends leaving it out unless you really need to shake your teeth loose.

Jett · **Joined:** Fri Apr 17, 2020 12:07 am **Posts:** 250

It’s only been in for 40mi so far

New tranny mods, strange drive behavior

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