2004 XC 70 engine/trans swap into 2002 V70 XC body

RobandHilary · Post by **RobandHilary** » 30 Mar 2022, 06:26

Hi there, we are new to Volvos, and are new members here.
We've done several other engine/tranny swaps in the past on non-Volvos without significant issues.
We were given a 2002 V70 XC with a good body but bad engine and transmission, and a 2004 XC 70 with a bad body but good engine and transmission. We installed the 2004 engine and tranny as a unit into the 2002 along with the computers.
At first the motor wouldn't start, so we tried putting the 2002 engine computer back in. Now it starts and runs but the transmission doesn't shift from third gear--it goes into Drive and Reverse but when in Drive, stays in third. We know there are computer issues going on, but would like to know which additional parts from the 2004 need to be installed to make the transmission function.
What is the best way to make the 2002 work with the 2004 engine and transmission? Hoping someone here may have some helpful tips. Thanks!

Post by **vtl** » 30 Mar 2022, 08:41

04 is 2.5T, 02 is 2.4T, right? I don't think it will be able to pass emissions, since the fuel trim will be way off and trigger an error. You may want a 2.5T ECM (engine computer) synchronized with 02 CEM. Yes, with Volvo it is not as simple as swapping a random ECM in.

In transmission you may need to swap S2 solenoid and remove B5 control spring in its late valve body: https://www.sonnax.com/tech_resources/2 ... tification

Also I don't know if the final drive gear ratio is the same in 02 and 04. Latter has 2.65:1. It think it is the same.

Post by **abscate** » 31 Mar 2022, 04:52

I’m not sure if you guys have emissions testing on a 2004 in the Green Mountain State.

You might need VIDA software to make your diagnosis on this. Missing a gear doesn’t sound like software but transmissions and software do change in the P2 platform.

Resources

There is a good garage in Burlington that knows Volvo software.

Doublebug, user here, is in CA but can do software tweaks over the internet for 1/3 the dealer cost.

Did you move over the 2002 TCM as well?

I’m surprised the 2002 ECM worked okay with the immobilizer and CEM on the 2004

That sonnmax outfit isn’t too far away!!

Sonnax Transmission Company 2 Imtec Lane, Bellows Falls, VT 05101-0440, USA
800-843-2600 · 802-463-9722
Contact Us

RobandHilary · Post by **RobandHilary** » 04 Apr 2022, 19:12

Thanks to both of you for your suggestions!
We ended up putting both of the '04's ECM and TCM in (with the '02 engine and transmission) and somehow now the car is running smoothly. We needed to redirect one wire to get the radiator fan running. Otherwise so far so good, car is running and sifting gears.
We are still unsure about the gear ratio--wondering if we'll have issues running the '02 engine/tranny with the '04 rear end. We had to swap out the flange that connects the drivetrain to the transmission, and seems like it will fit alright. But we haven't yet tracked down the gear ratio of the respective cars. Any tips on that subject are welcome!

Post by **firstv70volvo** » 04 Apr 2022, 19:53

RobandHilary wrote: ↑04 Apr 2022, 19:12 Thanks to both of you for your suggestions!
We ended up putting both of the '04's ECM and TCM in (with the '02 engine and transmission) and somehow now the car is running smoothly. We needed to redirect one wire to get the radiator fan running. Otherwise so far so good, car is running and sifting gears.
We are still unsure about the gear ratio--wondering if we'll have issues running the '02 engine/tranny with the '04 rear end. We had to swap out the flange that connects the drivetrain to the transmission, and seems like it will fit alright. But we haven't yet tracked down the gear ratio of the respective cars. Any tips on that subject are welcome!

If you're not getting gear ratios error codes or any other codes I would think you're in good shape other than maybe a mph error in the speedometer because the final drive ratio may be different.