Steve920

Wondering if the mounts are the same on these? If not what's the distance difference?

mrvedit

The 6L80E is a vastly bigger trans.
What are you trying to do?

Steve920

Im building a 46 hotrod and ordered a custom chassis. I gave them the details of going ls1 with a 4l60e. The chassis has come and I got a price on a ls3 with 6l80e that I'm considering. I know it's much bigger but wondering if my transmission mount on the chassis is going to do.

mrvedit

This thread might help you:
https://ls1tech.com/forums/conversio...80e-6l90e.html

Looks like the length is about the same but the diameter is greater for much of its length.

Steve920

Thank you. From that, I would believe the mounts to the chassis are the same. To confirm maybe I'll talk to someone from gm.

poorhousenext

I have a 6l80e conversion, did it back in 2007/2008. If I had to do it over, I'd never do it.

I'm no a fan of them. Gear spacing is made for truck use more than car. It's an attempt to get better gas mileage, not performance.

Might want to read through the thread below. Better be ready for a wider, higher tunnel in that 46 Hotrod. Trans's backbone is higher from bell housing to end, compared to 4l6oe. Also, don't plan on cars stance sitting low, even with shallowest pan.

When we did this, their was no way to tell what gear you were in. Speartech now offers a cheap gear indicator, at least. Paddle shifting or TU/TD shifting it isn't that great either. Sitting in a parking lot, you get to tell people you have a 6 sp or maybe they will see paddles if you go with them...LOL TU/TD they'll never notice.

https://ls1tech.com/forums/conversio...l#&gid=1&pid=2

Steve920

Thanks for the input. I may just go with a ls1 w/4l60e. I want to get my frame powder coated and was wondering on the mounts of both transmission in the case I end up getting an ls3 with a 6l80e. But from the sounds of your opinion maybe a built 4l60e would be better even if i went with the ls3. I did know about the tunnel size being bigger and all. Which is a downfall since I plan on chopping the top or channeling the body..

mrvedit

I'm glad that poorhousenext could give personal experience about the 6L80E because I feel the same way about it - it is more suitable for heavy trucks and SUVs than for performance cars.
I once considered purchasing a Pontiac G8 GT which came factory with an LS2 and 6L80. It was terrible - it lunged in 1st gear and then bogged down in 2nd gear due to the huge ratio change. I would consider an manual G8/GT now, but definitely not an automatic unless you swapped to a 3.73/4.11 rear and eliminated 1st gear of the 6L80 entirely.

poorhousenext

Steve,

Back in 2009, I started another build with an LS3 and ran into a problem with 4l60e and maybe some 4L65E too not being compatible with LS3 Computer needs. LS3 if I remember correctly needs both ISS IN and OSS out signal.Had to have trans modified to add the extra parts to make it work, but never used it as I went with another trans that could handle more HP/TQ than 4L60/65 could.

Might want to check this out and see if there is a work around now for it.

The two Pins circled in RED were missing so had to have trans modified to include them. If your 4L60 doesn't have them, you might to verify there is a work around for them now.

mrvedit

Yes, the ECM/TCM combo that comes with stock LS3 will need the ISS signal from either a newer 4L60E or 4L80E. There is no way to make a non-ISS 4L60E work with that, not even with clever tuning.
Many/most 4L60E/4L65E from 2006 will have ISS and all 2007+ 4L60E/4L65E/4L70E will have it.
Therefore, before buying/installing a 4L60E, make sure it has those two pins.

Steve920

Okay, I had no clue. Thanks! If I go ls3 and want a 4l60e I'll know what to look for now.