'97 850 GLT ECU swap to T5

[erikv11]

People used to do this all the time (and talk about it!) with 98's where everything is m4.4, less common with 850's as the LPT was only in one year the 97, and in 97 there was the split between m4.3 and m4.4.

With the bigger turbo the difference at higher rpms will be substantial, but you do lose some around town zippiness.

[503GLT]

Also, I swapped a 97 t5 into a 97 glt, so they should both be a 4.3 motronic, and it sounds like most people go with a 98 t5 4.4 and run into issues, so I’m curious If using bot ‘97 4.3 would make a difference?

[erikv11]

All 97 GLT were Motronic 4.4, as per earlier posts. But yes, it is possible a 97 m4.3 T5 is set up properly for the 97 GLT AC wiring.

[Chuck W]

All 97 GLT were Motronic 4.4, as per earlier posts. But yes, it is possible a 97 m4.3 T5 is set up properly for the 97 GLT AC wiring.

Yeah, I suppose that's possible, as there are no wiring differences in the HVAC systems between the GLT or other models (NAs were also M4.4 since '96), but as you mentioned earlier, the evap and a few other systems are different, and you'll probably wind up with DTCs or a CEL.

I had no plans to downgrade to M4.3 on the GLT and actually also did the M4.4 conversion to my '97 T5. I noticed faster starting and smoother running pretty much immediately, with no other changes.

For me the self-flashable MY98 M4.4 ECU was the way to go.