97 Saturn SL2 SL1 transmission swap

[Garthok]

Donor car: 1997 Saturn SL2 SOHC Automatic
Recipient car: 1997 Saturn SL1 DOHC Automatic

Can I just swap the transmissions or would I be better off swapping the entire engine/PCM etc.?

I know the DOHC has more power, and that the ratios in the transmissions are different. So I am leaning to the less powerful engine with matching transmission.

The donor car was driven under a utility truck by my mechanics daughter the engine transmission are undamaged.

the recipient car just has a bad transmission (no reverse/rough shifting in drive)

[PurdueGuy]

you cannot mix and match automatic transmissions with different engines. Because the gear ratios are different, the computer cannot control the trans properly, and you cannot get the PCM flashed for a DOHC engine and SOHC auto trans. If you're going to swap, you will have to swap both the engine and trans, along with the PCM.

[1995sl1sohc]

It sounds like you have a valvebody/input shaft nut problem rather then a bad transmission. A valvebody can be had for around $200 give or take a bit, input shaft nut from the dealer = $8, so for let's say $250 max and 3-4 hours of labor you'll be good to go again shifting smooth as silk and have reverse back. There is lots of information on this site dealing with valve body and input shaft nut problems do a search on them and you will have plenty to read about.

[Garthok]

Thank you, thats what I thought. I just wanted to be sure. both cars should have the same wiring harness though right? I might end up trying to get a transmission from pull-a-part in nashville ($43).

[fetchitfido]

With automatics you can only put a DOHC auto in a DOHC auto (or SOHC for both) of the same year, 2 year range if your lucky.

I like 5spds. You just have to find one (any year/model/engine) and put it in.

[Garthok]

Follow up: 97 Saturn SL1 DOHC -new valve body

1995sl1sohc mentioned the valve body replacement so I tried that.
Now I get a check engine light: 2nd gear incorrect ratio. and reverse is very slow. when I shift into reverse the car barely moves, when I step on the gas in reverse engine rpm goes up, but I crawl very slowly in reverse. There is no Bang, it shifts easily with no hesitation.

Anybody have an idea what I did wrong?

[Growser]

You did replace the input shaft nut, too, didn't you? You need to replace it as it can't be reused.

[Garthok]

I haven't tried that yet. I will have to do that tomorrow.

[virnin]

Originally Posted by Garthok

Follow up: 97 Saturn SL1 DOHC -new valve body

1995sl1sohc mentioned the valve body replacement so I tried that.
Now I get a check engine light: 2nd gear incorrect ratio. and reverse is very slow. when I shift into reverse the car barely moves, when I step on the gas in reverse engine rpm goes up, but I crawl very slowly in reverse. There is no Bang, it shifts easily with no hesitation.

Anybody have an idea what I did wrong?

I'm a little concerned that you're using parts from the wrong transmission. An SL1 should have a SOHC engine with the MP6 automatic transmission. An SL2 should have a DOHC engine with the MP7 automatic transmission. It's possible the valve bodies are not interchangeable.

[rickystarshine]

The valve bodies from a 1997 sl1 & 1997 sl2 ARE interchangable, check the fuses in the underhood fuse box marked something like TRS1/2 TCC & so on, these are the fuses for the solenoids in the valve body.
Also check the car's charging system & battery, low voltage will wreak havoc on the performance of these electronicaly controlled transmissions.
Make sure to have the proper fluid level as well, dexron III or equivalent.

Change the input shaft nut.

Good luck!

[Garthok]

All fuses are good, I bought a new battery when I bought the car my scan tool says voltage is 11.9V I noticed some small bubbles on the dipstick when I checked the fluid level, but the color and level is good and does not smell burnt. I am having difficulty locating a replacement input shaft nut. none of the local places have them, or even know what they are even with the part number. If anybody has one, could you post it on ebay with the gasket too?
Input shaft nut SN21001680
end cover gasket SN21001684

[1995sl1sohc]

You'll have to do the input shaft nut. Reverse and 2nd gear are closely connected. When the input shaft nut backs off from the reverse slam 2nd is the next thing to go.

The MP7 and MP6 transmission valve bodies are interchangeable, the only thing you have to look out for is valve bodies from 1991 and some 1992 cars as they have the first gen valve body design. You can tell the difference by looking at the bottom of the valve body, the 2nd gen's have 4 holes in a diamond style pattern on the bottom and the 1st gen will not.

Usually the end cover gasket does not tear and you can reuse it. They are both dealership items and the local parts store won't carry them. If you absolutely cannot get the nut, I assume you could remove the old nut put some locktite on it and put it back on and retorque it. I would much rather put a new nut on, but if I absolutely couldn't get one I would reuse the other one with some loctite.

[rickystarshine]

11.9 volts is low, should be at least 12.5 volts, check again to be sure.
check with the car running.

[Garthok]

with the car running it says 12.8V

[rickystarshine]

well, that's better...

[Garthok]

I just noticed that with my engine off my engine RPM is reported as 61RPM, is that normal? Running it idles at 830-865RPM

[madpogue]

Originally Posted by Garthok

with the car running it says 12.8V

That's also low. Could be alternator/wiring, or the battery. I've seen very weak batteries bring down the voltage even when the engine is running.

[rickystarshine]

Originally Posted by madpogue

That's also low. Could be alternator/wiring, or the battery. I've seen very weak batteries bring down the voltage even when the engine is running.

You're right, shouldn't it be around 14 volts with the car running?

[1995sl1sohc]

13.5 - 14.5 volts running with blower motor on full blast and headlights on.

[Garthok]

I will take the battery to autozone and have it tested, it is only a few months old.