Question to those who have JWT TCU and ECU

[redmanfx]

I'm not to terribly happy with the JWT TCU and ECU I just installed due to the continued hard jerking of the car between 1st and 2nd. To those who have this upgrade, how long before this hard shifting subsided a bit? How long did it take before the car learned your driving?

I know it takes time and that hard shift won't totally go away, but this is too hard a shift at times. The car also shifts at different RPMS. Sometimes at 5000, sometimes 4000 and sometimes 3200. This depends if I'm gradually increasing speed, stepping on it or moderately accelerating, but it's not learning fast enough. The hard shift at times is substancial and bothers me.

red

[911/Q45]

My 1-2 shift never changed, always pretty firm. I think the early cars with the lower first gear do it worse because of that low ratio.

[DominickJ30]

I'm not to terribly happy with the JWT TCU and ECU I just installed due to the continued hard jerking of the car between 1st and 2nd. To those who have this upgrade, how long before this hard shifting subsided a bit? How long did it take before the car learned your driving?

I know it takes time and that hard shift won't totally go away, but this is too hard a shift at times. The car also shifts at different RPMS. Sometimes at 5000, sometimes 4000 and sometimes 3200. This depends if I'm gradually increasing speed, stepping on it or moderately accelerating, but it's not learning fast enough. The hard shift at times is substancial and bothers me.

red

I think the whole point of the JWT TCU is to have those quick/hard shifts. Someone correct me here if Im wrong.

[Q45tech]

Sounds like your is working PERFECTLY to me!The early TCU prior to say 1997 have no real learning function other than to modify line pressure for clutch wear and to adjust line presssure for ATF temperature.

Self learning mean it tries to maintain as new shifts till it runs out of adjustment range [of line pressure] after the transmission wears in say by 60k.

If you will study your FSM you will see the shift points vs TPS voltage [% of load~~accelerator position] are normal.

Are you speaking of the basic JWT ecu or the advance selectable trimode version...........the only one to acquire.

Not having a perfectly adjusted TPS creates gaps / overlaps in how the transmission decides on which of 8 levels of load you are trying to achieve with accelerator position.

IF the engine is not producing as new torque at a shift point the transmission cannot perform as new.

Also JWT changes tip in WOT retard to return timing back to normal faster after a shift this may be some of what you are feeling with a worn transmission.

[redmanfx]

I think the best thing for me to do is to have a diagnostic done on my car. I want to make sure all is well. I've gone over the FSM a little too much lately due to everything I'm doing to the car and feel I've got that info down.

I want to know if I do have a perfectly adjusted TPS. The car has so many miles on it and no matter what new things I've put on or replaced, ala 25,000 mile JDM transmission, converted from active suspension, brakes, rotors and so much more, I feel I still may have a worn out old engine. A diagnostic run should ease my mind.

I know shift points and a hard shift come with the JWT upgrades and with the earlier models(mine is a 92) that may be even more severe, but I almost feel that something else may be going on here.

There is just no-where to go around here to get done what I need done unless I do it myself...... especially diagnostics.. which I simply can't do. I've done so much by myself I just want someone to confirm I've done a good job, but that can't happen around here. I have got to get to the dealership in Raleigh!!!

red

[Q45tech]

As soon as the new Atlanta Aquarium opens November 23, 2005 maybe we [T3] can see more taking the drive to Atlanta. Been very slow for distant out of staters recently. Just the usual Tennessee, Alabama, Florida, S.C. Regulars. We haven't bought but 1 dead Q this year.

http://www.georgiaaquarium.org/

[gniknave]

My car too has the hard shift and seems it won't go away. I prefer it to be hard and be able to feel it than to not be sure and have a thought in the back of my mind that my transmission may be slipping.

[maxnix]

Are you speaking of the basic JWT ecu or the advance selectable trimode version...........the only one to acquire.

I presume this statement only applies to the pre-1994 ECM?

[redmanfx]

Ok, I have it narrowed down to the shift points. I'm not happy with "where" the shifts are happening, meaning at what point the shifts actually occur. They are not at specific RPM's. It seems the shift points are all over the place. Is that normal? Anyone have the JWT TCU shift point specs?

One day I'll ride to 6000rpm before the shift from 1st to 2nd and the next it's 4,500 rpms and that's at the same acceleration. Day after that is shifts at 5,000 rpm. It just doesn't make sense to me.

red

[911/Q45]

Sounds like a failing trans.

[maxnix]

Sounds like a failing trans.

I agree. Tell us about the fluid, the pan surface when dropped, the material on the magnet.

[redmanfx]

Sounds like a failing trans.

I hope not. I got this from Glenn and he has a great rep here. I double checked and it had 30,000 miles on it when I got it.

red

[DrewQ45]

If the car didn't shift this way prior to the aftermarket control units, then I doubt that this is related to transmission failure. To satisfy your curiousity (and mine), why not go back to stock and see if the problem disappears?

I had a similar issue when I switched my 90Q's TCU to a 93' unit (this is done for first gear start). At WOT from zero, it will hold the shift and suddenly drop into 2nd gear with a stiff jerk. At high speeds, there is considerably more gear hunting resulting in less efficient shifts than compared with the original TCU. I tried going back to the original TCU and that produced perfect shifts, but I was too much in love with first gear starts and switched back. In light of this, I try to keep my WOT moments above 1st gear so no drag racing for me. If going on a long trip, I usually switch back to orginal for the high speed benefits.

On another note, there were two model numbers for the 93 TCU's. If anyone is having similar issues, and your model# differs, maybe we could perform a TCU swop to see if things improve? Ah... maybe I'll save it for another post.

....Drew...

[Jesda]

A 93-95 TCU produces a hard 1-2 shift for me as well. I wish 3-4 was firmer while 1-2 was softer.

[elwesso]

A 93-95 TCU produces a hard 1-2 shift for me as well. I wish 3-4 was firmer while 1-2 was softer.

I agree....

[redmanfx]

While the hard shift persist and is not really an issue for me anymore as I'm getting use to it, the shift points were. Today the Q is doing much, much better. I can cause a shift by letting of the gas a bit where as before I could not and the shifs are starting at persistant rpm's.

At WOT the car is a rocket from the start. Much more than I expected with the JWT mod. At high speed I don't see a gear hunting problem which I did look for at first. Like I said the difference in the car today in night and day as compared to the last 5 or 6 days. I went for a ride and it is still much more tolerable.

red

[Q45tech]

Nothing inside the transmission ---- controls when the shift starts to occur.........all from TCU which looks at speed sensor voltage from speedometer convertor IC [the 0-5 volt signal] and TPS voltage [0.4>4.4 v signal].

Some intermitent voltages: wiring, connectors, corrosion.

The turbine sensor vs speed vs rpm tells TCU when the shift has been completed. Remember the TCU just selects the appropriate solenoid engagement pattern and the ATF flow changes vis the lagging valve body does the work.

Why you flush annually to keep the varnish out of valve body to speed reaction times.

Another thing over looked is ATF age.........like oil ---- changes viscosity with age and temperature........which affects the shift [especially if ATF viscosity is not at the preprogrammed value expected for the ATF temperature sensor reading].

Why new ATF often makes a significant change in feel.

[PoorManQ45]

Try changing the transmission fluid. Use a high quality Synthetic, Possibly Mobil 1, AmsOil, or Redline.