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Old 08-05-2016, 05:55 AM   #1
sedlmtim
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Cool 97 SL1 single cam manual transmission swap to 98 SL2 dual cam auto transmission


So I have my old 97 saturn sl1 sitting for parts to my new 98 sl2 seeing i have done alot of work to the 97, keeping it running. well recently it has been misfiring alot and lost alot of power, the engine just runs like crap. so i got this new 98 sl2, and it has the power windows, locks, keyless entry, cruise control, all the things my old one didn't. my last one was all manual, including the transmission, which was my favorite thing about it, it had alot of get up and go compared to all my other cars, seeing they were auto. and I HATE the automatic transmission, its way too slow compared to the manual, even considering the lack of power. is it possible to swap my manual transmission from the 97 sl1 sohc to the 98 sl2 dohc? i have heard of it throwing ses codes because its an auto computer. ive also heard things about rev limiters as well, and i do know most of the parts that i would have to take from the other car, and i do want to get a new clutch kit as well. would i also have to switch my sl1 computer over as well, and would i lose my power locks, cruse control, and my keyless entry? i'm aware that its a bit of work but im thinking seriously about doing this. any help would be greatly appreciated.

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Old 08-05-2016, 08:01 PM   #2
derfderf
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1) As far as I know, an SOHC PCM cannot control a DOHC. And even if you did bring the PCM and wiring harness over to the 98 to make it think it was a 97sl1, it is very likely that you'd have no way to connect the power options and cruise, etc, because those parts of the wiring harness would not be present. I suppose you could strip one from a fully optioned junkyard car to address that, but again, I don't believe an SOHC PCM can control a DOHC.

2) I BELIEVE 98 was the year that they added the air pump stuff, so your 98 should have it; the 97 wiring harness will have no provisions for wiring and will throw codes constantly.

3) The fun of a manual DOHC is to a large degree the manual tranny gear ratios. It is geared significantly lower than the SOHC tranny so that it pulls harder off the line and for the first few gears.

So while a manual Sl1 trans will bolt up to the SL2, the gear ratios are not the same, it WILL run and drive, but I don't know if the performance increase you seek will be there with the less aggressive SL1 tranny in there. Additionally I believe you get constant "Incorrect gear ratio" codes that get thrown constantly.

4) PCM from a 98 to ? for a manual trans vehicle would have to be used. Whatever PCM you put in will need to be flashed to match the options of the car. I do not believe you can FLASH AWAY the manual/Auto demarcation. Which means hunting for a 98 to ? DOHC manual tranny PCM and getting it flashed to match the options.

It cannot be a manual 97 DOHC (I have one) PCM as there are no provisions to control the air pump from 98 on.

99-2002 Saturn introduced a BCM (Body Control Module) to offload control of many things to it. I have no idea if the PCM is physically compatible and just programmed differently or whether it is a completely different animal.

Conclusion: If I understand what your after, which is better performance out of your 98SL2 with a manual transmission, the SL1 manual transmission will NOT deliver you what you seek.

It'd be less of a hassle to buy a used manual DOHC tranny and a used 98 manual DOHC PCM flashed to match your options
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Old 08-05-2016, 08:02 PM   #3
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And fix the 97sl1..

Start a new thread and post the codes (Pxxxx) and we'll work from there.
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Old 08-05-2016, 08:37 PM   #4
sedlmtim
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okay, i understand what you're saying. so could i take a computer from say, a 98 sc2 with power windows and locks, and use that computer in my 98sl2? i'm not looking to seek a very high increase in performance, i just want it to have a little more get up off the line. I was looking more into the transmission swap from the other car because it would be much cheaper. i was thinking of trading parts from the other car for the transmission and computer, from a guy that runs a junk yard, i've gotten saturn parts from him before. I'm not expecting a whole lot more performance out of the swap, just expecting it to feel like the sl1 did, if not a little bit more. and the transmission from the sl1 has 189k on it, and the 98sl2 has 154k. when i ran the codes a while back for the sl1, the check engine light wasn't always on, only periodically, then it started staying on all the time. it showed an oxygen sensor, and the exhaust is in very rough shape, i feel that at this point the car would cost far more money than i can afford to fix, hence why i have the 98 sl2 now. if i took a pcm from another car with all the features of my 98sl2, i would try to match everything right to be sure it would work. i don't want it to be thrown back together with lights flashing everywhere, i want it to look standard for the car.
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Old 08-06-2016, 03:47 AM   #5
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Indeed. b/c of the difference in gearing, a SOHC tranny paired w a DOHC engine will not give you the kick you're looking for.

Again, a 98 DOHC PCM from a MANUAL transmission 98 DOHC car + manual DOHC tranny should work. I believe it can be any MP2 (manual) tranny. But the newer ones will likely have fewer miles. If there is any fluid left check for burned fluid. Check the cooling lines to make sure they will bolt up.

I believe the 98 DOHC PCM can be reflashed to match your current options.

Look up the GM part numbers for the DOHC Manual tranny PCM and the different year of MP2 trannys. I know there was a gear change in the latter half on the 90's so the part number may change but it should still be a bolt up.

USE THE ABOVE INFO AT YOUR OWN RISK.

Which means double check it, crossreference, find the exact same swap on the net and see if they ran into problems w newer MP2 trannys, etc. I don't do saturn swaps for living and I am not attempting to portray my self as an expert in the area.

Hopefully sc2sick drops by and thumbs up or shreds what I have posted.

This is a pretty simple swap if you're doing just Auto to Manual.

Lemme know what you find on the part num search before you pull the trigger on this
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