Hi guys! I am swapping a 6.0 truck engine into an 89. I know it’s been done before so that part is no big deal. Because I have neuropathy in my feet I have to also switch to an automatic. I have always loved the C-2/3/4/5 generations the most. This time it will be an 89. My intention is to swap out the packman dash to analog gauges. For now the trans will be a built 700R4. Why? because I already have one. So I am looking for input. If you have done this and went along with what I’m doing or decided to do a different way your thoughts are welcome. If you see in future posts something I have not considered or something I could do differently chime in. I hope to document (with photos) this build as I go along to help the next guy along. THE CAR: It’s a 1989 Coupe that was in a fresh water flood so for now it’s a roller the ZF was locked up and so was the engine they are gone. The interior was stripped out. It’s been in storage as I haven’t been able to get it in my barn, I will be soon moving it inside. As you can see it’s early in the process.(end for now).

 

So I'll play devil's advocate here. I've had two different transmissions with two different LS engines in my 84. I started with a 4L60e and now have a 4L80e. I know you already have a 700r4. But if it were me I would sell it. If it's built you could probably get a lot for it. Sell it and go pull a nice low mileage 4L80e out of a 3/4 or 1 ton Express van. You will need a new driveshaft but for the 700r4 you needed one anyway. Then no TV cable and a way stronger foundation. If you trash the thing you can go get another one for $200 from most any u pull it salvage yard. With a smaller billet converter the weight difference between a 4L80e and a 4L60e is only 20 pounds.

I went with aftermarket gauges in mine. One thing to be mindful of is what ECU are you going to use. This plays a roll in gauge selection. I used a Holley Terminator X max. The gauge outputs from that ECU are a negative pulse (NPN) only. Most aftermarket gauges can't read that signal. So I had to use either pull-up resisters or transistors to convert the signal to a positive (PNP) signal. Not a huge deal just annoying.

For a driveshaft the best shop I have ever dealt with was Action Machine. Their head machinist is a guy named Bob Guzman. His work is incredible and their prices are very good. I up sized my driveshaft to a 1350 yoke with steel and upped the tube size a bit and that shaft was only $250. I had him make me steel half shafts also.

Will a 700r4 work with an LS....yes. but it will go a lot smoother if you sold it along with your pac man gauges and get something computer controlled and go that route. But that's just my opinion.

 

Ok I like what you said I got a 4L60 core for 200.00 and I have the four bolt tail shaft housing to fit the support channel. But the 4L60 has a six bolt end on it? Did they do a four bolt tail? how do I connect the support beam?

 

You fab an adapter. You need a 4 1/2" chunk of box steel that's around 1/4" thick and around 12" long. You'll also need some 1" bar stock around 1/4" thick. I've made two of these now. One for the 4l60e and the one that's in the car now for the 4l80e. I take the transmission and bolt it to an engine stand and start test fitting. If you do a search there are a couple different versions that people made and posted threads about how they did it. It just takes a little creativity and a welder. Total cost is under $100.00 in steel. I ordered the box steel online and I already had the bar stock. 4 1/2" box is a goofy size so you might have to hunt to find it.

After re reading your post I was mistaken on something. Going from a manual to an auto you wouldn't need a new driveshaft. The factory one you have would fit with either a 700r4 or a 4l60e. You would need a shorter one for a 4l80e.

​​​​edit....In case you're interested I found the old thread I made back when I made my 4l80e c beam adapter. The search on the forum seems messed up. I had to find it using Google.

https://www.corvetteforum.com/forums...dana-44-a.html