auto box swap -which ecu do i use ?

volrod544 · Jun 25th, 2019, 21:36

I lost drive on my 850 t5r and have now gone about changing the autobox and torque convertor from another 850 which was a 2.5 non turbo . the gearboxes are both 50-42le models but the ecu,s in the cars were different,do i continue to use the t5r ecu which i think was a 5.2 or do i use the one from the 2.5 non turbo which i think is an 11.2 ?

CNGBiFuel · Jul 1st, 2019, 10:13

I've got a similar job to do, and in my case it's like-for-like. Nonetheless my gut feel is to keep respective ECU together.

scutyde · Jul 3rd, 2019, 13:58

The n/a box has different gear ratios, if you keep the TCM from the original box it will throw DTCs for incorect gear ratios and maybe also go into limp mode. Also afaik the turbo gearboxes have stronger components.

The TCM also sends to the ECU in the 1st and 2nd gear a signal to keep the boost level lower in order to minimize wear on the components. Not sure if the n/a TCM supports this option. Think it does it also when the gears are changed.

volrod544 · Jul 13th, 2019, 19:36

ended up using the original t5r ecu. heard the gearboxes are the same but the torque convertors are different ratios ?

Jun 25th, 2019, 21:36	#1
volrod544 Member Last Online: Oct 18th, 2023 18:53 Join Date: Oct 2004 Location: norfolk	auto box swap -which ecu do i use ? I lost drive on my 850 t5r and have now gone about changing the autobox and torque convertor from another 850 which was a 2.5 non turbo . the gearboxes are both 50-42le models but the ecu,s in the cars were different,do i continue to use the t5r ecu which i think was a 5.2 or do i use the one from the 2.5 non turbo which i think is an 11.2 ?

Jul 1st, 2019, 10:13	#2
CNGBiFuel Classic P80 1999 BiFuel Last Online: Mar 6th, 2024 00:34 Join Date: Aug 2012 Location: 48mph Middle Lane M4	I've got a similar job to do, and in my case it's like-for-like. Nonetheless my gut feel is to keep respective ECU together. __________________ Bifuel V70 Classic 1999 [The Old Grumpy in the Corner, "When I was a lad... blah, bl**dy blah."]

Jul 3rd, 2019, 13:58	#3
scutyde Retrofit master Last Online: Mar 28th, 2022 10:14 Join Date: Mar 2010 Location: Berlin	The n/a box has different gear ratios, if you keep the TCM from the original box it will throw DTCs for incorect gear ratios and maybe also go into limp mode. Also afaik the turbo gearboxes have stronger components. The TCM also sends to the ECU in the 1st and 2nd gear a signal to keep the boost level lower in order to minimize wear on the components. Not sure if the n/a TCM supports this option. Think it does it also when the gears are changed. __________________ Volvo 850 2.5 20V MY95 Pictures Here what I retroffited so far List

Jul 13th, 2019, 19:36	#4
volrod544 Member Last Online: Oct 18th, 2023 18:53 Join Date: Oct 2004 Location: norfolk	ecu ended up using the original t5r ecu. heard the gearboxes are the same but the torque convertors are different ratios ?

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