I have a 1989 RS with a 355 and 700R4. The 700R4 was built by Bowtie Overdrives and is the level 3. It's a great transmission and I'd like to keep it if possible. I'm thinking seriously of doing a LS1 swap and I wondered if I can bolt it to the 700R4. I've done some searches and some say yes, some no, and some say there is an adapter plate needed. Who has done this swap? Can I use my present trans crossmember? Will the transmission stay in the stock location?

Thanks

 

I'm in the middle of planning a similar project.

I'm pretty sure that the LS1 and the 4L60E transmission along with the computer that controls them need to be kept together as a system.

The 4L60E is a longer tranny than the 700R4 and therefore requires a mod to the trans crossmember, or a shorter driveshaft.

This is all just info that I've been gathering up to this point and I hope I'm correct. If I'm wrong, I hope someone will correct me on this.

Also Edelbrock has introduced a carb intake for the LS1, which their ad claims, allows the LS1 block to be mounted to the 700R4 or TH350 (also TH400, I assume)

I've been taking a keen personal interest in that concept, in spite of the fact that it makes the EFI die-hards cringe.
Because for my own application it makes more sense than anything I've found so far.
The carbed LS1 is a swap that I feel completely confident about, whereas swapping the EFI LS1, tranny, ECM and all the other related equipment would be overwhelming.

 

I read something in another thread that says the 700 can be used, you just have to leave one Bell housing bolt out. Never done it, cant say for sure, just what I read.

 

I posted about this topic in the other forum ljnowell mentioned. I read an article in either four wheeler or 4 wheel and off road where they swapped in a 6.0L into a suburban or blazer, and they bolted a 700r4 up to it. It has all the bosses in the block for the standard transmission, but you may have to drill and tap them, not real sure on that either. I will go recheck the article later and repost. They used all the holes except the one by the number 8 cylinder because if they tried to drill and tap it they said it would break through the cylinder wall. They did note that they had no problems with it holding on good with just the 5 bolts.

Adam

 

Hmmm, yes I posted about this on another thread so I will just copy and paste.


The 700R4 will indeed bolt right up to the LS1 with the exception of missing one bolt which is no concern. No you will not need a bellhousing adapter plate. All you need to worry about is your spline, between the older and newer 700R4s. If you have an older 700R4 or you are using an LT1 TC than you will need a flexplate adapter, which you can get online or any machine shop can make. Its about as round as a CD and a 3/4 of an inch wide and all it does is allows the shorter rear shaft on the TC to fit into the back of the LS1 flexplate. If you have a newer 700R4 you can use an LS1 TC... or an LT1 TC, but then you would need the adapter. I run an LT1 TC with the adapter.

To get your 700R4 to work with the LS1 computer correctly without the computer throwing a code when it cant find the 4L60E is you will need to have your PCM flashed to a Manual PCM instead of the Auto.

About the 4L60E being longer. That is not true. The T56 isnt longer either, but the mount sits back farther so you will need a new tranny crossmember if you went that route. Otherwise a 700R4 crossmember will work fine with a 4L60E. And about the Driveshaft... Any 4th gen driveshaft is the same length as the 3rd gen.

 

Sorry about the misinformation I passed along about the 4L60E being longer. I'm not sure where I got that, but now that I know the truth, I won't say that any more.

 

Thanks to all of you for your info. My 700R4 bolted up to my stock 305 TBI (1989). I then changed to a carbed 355 and it fit. Is the 1989 late enough to fit the LS1?

 

There are a couple parts listed on the Edelbrock site for use when mounting an LS1 to a TH350, TH400, or TH700R4
Those are Hughes Performance #HP3795 crankshaft sleeve and #HP4004 flexplate.
800-274-RACE is the ph#