Transmission Help!
Thread Starter
Cruising
Joined: Jan 2009
Posts: 14
Likes: 1
From: Morton Grove Illinois
Transmission Help!
I bought a new GM LS3 engine, 430hp for my 1981 corvette. I currently have the stock automatic 350 transmission. I have a few questions:
1. Is there any recommendation for an auto trans I can use with the LS3 that does NOT require cutting into the tunnel, changing driveshafts, and changing crossmembers?
2. The LS3 I bought came with wire harness, throttle pedal, and ECM. My question is will the ECM that came with the engine also control the transmission that I get or will the Trans need a different/separate ECM?
3. Anyone out there have an LS3 mated to their 350 trans? If so, how is the combo?
Thanks in advance, everyone!
1. Is there any recommendation for an auto trans I can use with the LS3 that does NOT require cutting into the tunnel, changing driveshafts, and changing crossmembers?
2. The LS3 I bought came with wire harness, throttle pedal, and ECM. My question is will the ECM that came with the engine also control the transmission that I get or will the Trans need a different/separate ECM?
3. Anyone out there have an LS3 mated to their 350 trans? If so, how is the combo?
Thanks in advance, everyone!
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,116
From: Crossville TN
Don't know what trans programs are available in that ECM, but you should be able to find out on the web. I can say with some confidence that you don't want to put a THM-350 behind it; I don't even know if you can beef a 350 up enough to be compatible with that engine.
A 4L60-E will probably fit in the C3's trans area (it is essentially a 700-R4 with electronics); that is likely your best bet if the ECM will handle it. The 4L80-E will not fit without some significant modifications. The 4L60-E can be beefed up to your needs without much effort.
If you don't put an electronic trans in the drivetrain, the 700-R4...beefed up appropriately (many aftermarket builders have them already available)...would be a good choice. It has a lockup clutch which SHOULD be turned off when you want to 'pour the coals' to it. The L/U clutch is a good thing for normal driving...and especially for highway driving, so I would suggest a well-built O/D trans with L/U would be the way to go.
A 4L60-E will probably fit in the C3's trans area (it is essentially a 700-R4 with electronics); that is likely your best bet if the ECM will handle it. The 4L80-E will not fit without some significant modifications. The 4L60-E can be beefed up to your needs without much effort.
If you don't put an electronic trans in the drivetrain, the 700-R4...beefed up appropriately (many aftermarket builders have them already available)...would be a good choice. It has a lockup clutch which SHOULD be turned off when you want to 'pour the coals' to it. The L/U clutch is a good thing for normal driving...and especially for highway driving, so I would suggest a well-built O/D trans with L/U would be the way to go.
Last edited by 7T1vette; May 14, 2016 at 11:10 PM.
Safety Car
Joined: Jan 2009
Posts: 4,000
Likes: 299
From: New York
He has to use an electronic trans if he wants it to be simple. 4l60e . the 4l80e fits like a glove as well ( I have one in my 1980) but for your 430hp the 4l60e is plenty .
You will mod the cross member and you will change drive shaft length . BTO sells a cross member plug and play for the 700R4 which works perfect with a 4l60e
You will mod the cross member and you will change drive shaft length . BTO sells a cross member plug and play for the 700R4 which works perfect with a 4l60e
Thread Starter
Cruising
Joined: Jan 2009
Posts: 14
Likes: 1
From: Morton Grove Illinois
He has to use an electronic trans if he wants it to be simple. 4l60e . the 4l80e fits like a glove as well ( I have one in my 1980) but for your 430hp the 4l60e is plenty .
You will mod the cross member and you will change drive shaft length . BTO sells a cross member plug and play for the 700R4 which works perfect with a 4l60e
You will mod the cross member and you will change drive shaft length . BTO sells a cross member plug and play for the 700R4 which works perfect with a 4l60e
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,116
From: Crossville TN
You will have to get some expert advice about whether that transmission, as it is, will handle that kind of torque/power. Research it well; you don't want it to 'bite the dust' early. If you know someone in the transmission repair/rebuilding business (local...not a national chain store), they might be able to tell you what needs beefing up--or maybe be able to beef it up for you. I'm sure it will be a good trans, once capable of handling that new engine. And I'd bet it will integrate with the engine and ECM you already have.
