TCU Help

[yiannitQ45]

i want to swap my 90 tcu for the first gear tcu. My question is; i have heard the 93 tcu matches best for the 90 but is it a 94 model built in 93 or from a late 93 model? or could you give me the code that i should look for on the tcu.

[goody90q45]

The first gear start TCU from a 93Q is P/N 31036-64U20. A TCU from a 94 or 95 will work just fine also.

But, if you're wandering through a junkyard bring the VIN post with you. Only 12,000 93's were made and there's a gap of over 40,000 for the VINs in the 93 model year. Look for a Q with a hood buckle in the 250,xxx VIN range (late 93) rather than the 220,xxx VIN range (early 93). If no luck then grab a TCU from a 94 or 95 Q. It will work fine. Good luck.

zerothread?id=368173

[elwesso]

also if you're thinking about getting an upgraded ECU, the 94 TCU actually works better than the 93 because of the different gearing.

[yiannitQ45]

thanks for the help mike

[yiannitQ45]

so wes, you are saying if i want to get the Nico TCU for my 90 the 94 for will work better, but i thought the 94 had different gearing from the 90 so it wouldn't work as well. if this is so im hoing to the local pick n pull because they have 3 94 all with the TCU in them

[elwesso]

Heres the deal.. The 94 has a lower (numeric) gear ratio than the 90, something like 15% difference... Not a ton, but a little.

In day to day driving, youll never know the difference.. When you go to WOT and the engine reaches 6900 RPM, the TCU will actually hold the shift for a slight second.. The TCU doesnt read engine RPM's, it reads driveshaft speed.

The long and short of it is, with a proper 93 TCU and a NICO ECU your car will still shift at 6900 RPM, if you want to rev out to the 7300 RPM programmed redline, you have to hold the gear manually with the shifter.. With the 94 TCU in a 90-93 car and the NICO ECU, because of the difference in gearing, it will actually shift at the higher redline..

Kind of an unintentional side effect of the difference in gearing, but it works!

[yiannitQ45]

thats awesome! i guess i need to go pick one up then.from any 94 right? i will also contact you within the next month or so for a nico ecu, i just need to take care of some things with my q before i buy a new ecu
Modified by yiannitQ45 at 9:30 PM 1/3/2010

[Q45tech]

The 1st and 2nd gear difference in 1994 and later is more like 8 % and 4.2% not 15%

1st 2.784:1 2nd 1.544:1 vs 1st 2.569:1 2nd 1.479:1

This nets out to about 4-5 mph in each gear that the tcu might be off roughly the same amount that an extra 400 rpm rev limit creates why the ECU software change helps [solves hitting limiter before transmission shifts].

[yiannitQ45]

thanks everyone for the helpful advice