Transmission option for LSx swap
 

Hello everyone,

I have a 1971 C20 with 350/350 combo that I will be swapping out for an LS engine. I've recently purchased a 5.3 L59 engine with DBW out of a 2004 GMC Yukon 4x2. It is a complete engine pull with wiring harness, ECM, gas pedal, etc., but no transmission.

I need a transmission. I know a 4L60E is mated to this engine originally. After looking through craigslist and ebay, I'm overwhelmed by the various types of vehicle this tranny goes into. I have some questions below.

Should I look for a 4L60E around the same year as my donor vehicle or will newer units from similar truck work, also?

Is a used 4L60E with less than <75K miles still serviceable or should I look at a rebuilt one?

Does a rebuilt 4L60E come with electronics or do I have to buy them separately?

I know I can use a 700R4 with this engine. Is there a pro or con with using this transmission? I am leaning towards the 700R4 partly due to no electronics involved, thus less things to break. But if the con out weights the pro, then the 4L60E it will be.

I'm also unsure if the wiring harness from the engine has the TCM (transmission control module?) with it. The engine is on its way to my house right now. I should get it by this Friday. Not in a hurry to buy the tranny, yet. I'm still in information gathering mode.

This is my first restore/mod project truck that will be used for towing a small bass boat on occasion. I will post pictures once I've gathered all the parts for my build.

Re: Transmission option for LSx swap
 

I wish I could help, but my 2008 5.3L / 4L60E had a separate TCM. I'm not sure if 2004 was the same. I would think that the 4L60E would be easier to install. It's just plug and play. The 700R4 would require a TV cable, which could prove difficult to hook up with a DBW system. Just my $.02.

Re: Transmission option for LSx swap
 

700r4 would require you to switch to a cable throttle body so the TV cable has somewhere to attach. I am running a 4l80e and my main harness and computer take care of both the engine and trans. It would be the same if i were running a 4l60e. My engine is a 2003 lq4 with DBW.

Re: Transmission option for LSx swap
 

Go with a 4l60e, it will be the easiest/best option for you for the above reasons.

Re: Transmission option for LSx swap
 

The PCM controls the transmission, No TCM needed. I vote for the 4L60E also.
It will have to be from a LSx truck or car 4.8, 5.3, 5.7, 6.0.

Re: Transmission option for LSx swap
 

hey Chris! how ya are?

Re: Transmission option for LSx swap
 

Doing fine John, When is the next get together? How is the cruise control coming along?

Re: Transmission option for LSx swap
 

Cheapest/easiest route would be bolting on an old school turbo 350/400. I just finished doing a friends ford pinto (no joke) with a 05 4.8 and a turbo 400, piece of cake, and trust me he gets respect from some camaro owners..

Re: Transmission option for LSx swap
 

debatable. IIRC you need an adapter to run the oldschool trannies with the ls block engines don't you? With that cost, and the fact that most 350s and 400s you find around are tired or need a rebuild I would assume the a 4l60e could still come in as the cheapest option. Besides theres the benefit of having an o/d tranny.

Re: Transmission option for LSx swap
 

True that brother, but old school trannys are waaay cheaper (if found in good condition) than a 4L60, the adapter/bolts will cost u around $120 new.

Re: Transmission option for LSx swap
 

Being DBW is going to limit your trans choices. 4l80e, 4l60e, TH400 if you can rig the kick down switch directly to the pedal and maybe powerglide(no idea, never been near one) or manual will be your only choices. If you convert to DBC you can use a 200, 700 or 350.

Re: Transmission option for LSx swap
 

I dont know when the next get together will be, I tried putting one together but I only had one person say anything about it, it would have been this coming weekend too.

I really isnt, I had some damage from the storms a few weeks ago so my play money went to repair money and now is all but gone.

I will do the cruise, just be a while longer.

Re: Transmission option for LSx swap
 

Thanks for your advice guys. I will be going with a 4L60E instead. Seems like a less complicated route to take. 3 speeds tranny is not an option since I'm looking for improve fuel economy.

I just bought an ECE engine mount kit and transmission crossmember. Will I need to get a shorter driveshaft with this engine/tranny swap?

Re: Transmission option for LSx swap
 

I had to have mine shortened with the ECE kit.

Re: Transmission option for LSx swap
 

with me engine in the "front" position and a 4l80e, I had to get a longer shaft made to 57-1/2 inches.

Re: Transmission option for LSx swap
 

4l60e is a hair longer then the 80e. I got lucky and was able to use my stock driveshaft with a 1310/1350 Conversion U joint.