can i use a 1994 tcu in my 1990 q45?

Post by **subtle_driver** » Tue Oct 28, 2008 9:19 pm

just wondering, i tried searching but didn't get a definite result. does the 94 tcu work on my 1990? if so, does it plug and play or do i need to modifiy?i hear the 1994 tcu starts in 1st. My tcu starts the car in 2nd, and that isn't too good for the transmission. I would like to make my car start in 1st every time to make the transmission last longer and just because thats what i want! lol.

thanks

Post by **MinisterofDOOM** » Tue Oct 28, 2008 9:43 pm

2nd gear start isn't bad for the trans. Why would Nissan engineer a $50,000 car in a way that would cause it damage? Earlier Qs had shorter 1st and 2nd gear that made the 2nd gear start adequate for average driving but left 1st available when needed. Later Qs with 1st gear start from factory had taller 1st and 2nd gears which suited the new TCU program.

In answer to your question, though:Yes, a '94 TCU will work with your '90.

Post by **Q45tech** » Wed Oct 29, 2008 2:05 am

The 1993 TCU is the ideal swap since it also starts in FIRST and better matches the gear ratio since TCU uses speed sensor to select exact SPEED for WOT shifts..................94 and later ecu often conflict with rpm limit [6900] and you can get situations where the engine hits limiter before a shift.................this shows up more as transmission ages away from new or remanned.

If you reprogram rpm limit to 7300 instead of 6900 you avoid this problem in 1st and 2nd gears.

Post by **Q451990** » Wed Oct 29, 2008 2:38 pm

MinisterofDOOM wrote:2nd gear start isn't bad for the trans. Why would Nissan engineer a $50,000 car in a way that would cause it damage? Earlier Qs had shorter 1st and 2nd gear that made the 2nd gear start adequate for average driving but left 1st available when needed. Later Qs with 1st gear start from factory had taller 1st and 2nd gears which suited the new TCU program.

Not entirely true... the '90-'92 had 2nd gear start, but the '90-93 had the same transmission. The 1st gear start keeps the transmission cooler and should improve it's servivce life. I think Nissan switched to the 1st gear start partially in response to transmission failures in the early Qs.

The only advantage to 2nd gear start would be smoother starts and better control in ice and snow.

Heath

Post by **subtle_driver** » Wed Oct 29, 2008 7:04 pm

thanks for that info!

So it seems a 93 tcu is the best for a stock ecu. and when i tune my ecu i will want a higher rev limit and the 94 tcu will work out better for me!this is excellent info! thanks again!

Post by **Infinitiguy19** » Wed Oct 29, 2008 7:12 pm

Actually from what I hear (forget the source but it was on NICO) same matching ECU's and TCU's make for better red lines true or not I can neither confirm of deny for sure because I have noticed no difference, And I have 2 different other sets.

I have the stock original ECU and TCU

1994 Q45 Cali ECU and TCU

and a 1991 Q45 fed ECU.

But if you find a TCU from a really early 1993 Q45 then go with it as long as it has the older transmission, because mine is a 1993 Q45 build date 11/92 and I have the newer transmission.

I know that because mine has a screen in front of the bell housing

And I called up infiniti to see what transmission it calls for.

can i use a 1994 tcu in my 1990 q45?

can i use a 1994 tcu in my 1990 q45?

Re: can i use a 1994 tcu in my 1990 q45? (subtle_driver)

Re: can i use a 1994 tcu in my 1990 q45? (MinisterofDOOM)

Re: can i use a 1994 tcu in my 1990 q45? (MinisterofDOOM)

Re: can i use a 1994 tcu in my 1990 q45? (Q451990)

Re: can i use a 1994 tcu in my 1990 q45? (subtle_driver)

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