Transmission swap
 

I am going to be replacing my transmission in my 03 LS. Does anyone know if its easier to take the engine and transmission out together, or just the transmission by itself?

I'm not so sure you can even take out the transmission by itself, if you do its going to not be very easy. I would suggest dropping the subframe and going from there.

Definitely need to drop the cradle to access

I was reading in my Haynes manual about taking the transmission out and it seemed really overly complicated compared to other transmissions I've pulled. That's what made me wonder if it would just be easier to pull the whole thing engine and all.

They aren't too hard to remove the engine from the top. But you'll have to drain a lot of your fluids that way.

Does anyone know if there's a difference between the transmissions in a 3400 car and a 3800 car? Are they interchangeable? I know the l67's have a different transmission. But will a transmission from a naturally aspirated 3800 work in a car with a 3400?

The gear ratio is different

Just find another tranny from a 3400, and pull everything out of the top. You COULD do it from underneath and drop just the tranny but it's MUCH easier having everything out in the open. Especially where the bolt is on the back of the engine/tranny

Thanks for the info. I'm not totally sure what I am going to do. If I'm going to pull the engine and transmission to replace the tranny, I'd like to do a 3800 swap. Just not sure what I want to do.

the 3400 and the 3800 have diff trany's i still think the 3400 has a 4t60e and the 3800's have the 4t65e's

Whatever transmission is with the 3400, it sucks. I've had GM transmissions with 250,000 miles on them that still run like new. This one only has 109,000 on it and it's just about shot.

I thought in 97 GM switched them all to 4t65e

I emailed Will at Overkill to see if he could reprogram my computer to run a transmission from a 3.8. He said he could, but he also suggested getting a transmission from an Impala with a 3.9. He said the gear ratio is better for performance. Has anyone done this? If so, is it a direct bolt in, or are there modifications needed? He said pretty much everything from 2003 and up is interchangeable.

97 everything but the L67 was the 4T60E. 98 Everything was the 4T65E. The transmission from the 3.9L will be the same tranny. All those GM FWD V6s have the same bellhousing bolt pattern which eliminates that potential issue.

The N/A transmissions usually have a lower (numerically higher) gear ratio than the L67 transmissions.

Found a pretty good price on a transmission from an 06 Impala with the 3.9 with only 9,000 miles on it. Thinking pretty hard about going that route. The only other concern I have is the electrical connectors. Anyone know if they are the same on all the 4T54E transmissions?

I've never heard of a 4T54E tranny, but you shouldn't have to mess with the wiring or anything as long as you get a 4T65E tranny from a 3400 or 3800 Monte/Impala/Grand Prix. You should be able to find them pretty easily for about $200-500 used.

Oops. I meant the 4T65E. Sorry.

Get one with the hd diff and just swap it in from a gtp

The only thing though is that the 4T65E-HD has a different gear ratio and the PCM would need to be tuned in order to accomidate that. You could get a 4T65E and then do an HD diff swap, but that's a lot of work for no real gain except for a little more durability.