Auto transmission swap

When I use the search function to look for information on a transmission swap its all on the three speed. My van has an automatic. Does that mean that I dont have to change anything around to swap out the powerglide?

I want to put a 700R4 in it. What kinda things do I need to do if anything?

I knew it would need to be shortend. I wasnt sure about the mount though. Thought that maybe since it had an auto it wouldnt need to be modified for another.

Alright. I get the mount part then.

Can you explain the front yoke thing more? Thats something I would have to do if I use the vans driveshaft, right? What if I used a shortend driveshaft that came with the 700r4, is that possible?

The TH350 & 700R4 yolks are the same if that helps.

Don's 1st picture is of the TH350 and "support system" that was in my Van when I bought it.

The 2nd picture is of the 700R4 and 8" drop crossmember that's in it now. Well not right now, it's all been pulled back out so to paint & undercoat the underside of the Van.

Would you be able to make another one of those? I would pay you of course.

I dont know many folks with shops in there garage that could help me with this. Plus you obviously already have it done right.

Well ok then. I will look into that.

Also I just thought of this. When you (donivan65) where talking about how short the driveshaft would be, is that for a 90" van? Cause mine is the 108". I would guess that would make it easier?

Good topic!

I have 3 speed auto in my van with a strait 6 250..

I have been thinking about changing the tranny for one with longer gears for better highway rpm.. right now it screams down the highway top keep up with traffic, so i just drive slow and get there when i get there kinnda thing.

Now that I know its this big of a deal, how about this idea...

I have been toying with the idea of just changing the gears in the rear end and lowering all the gear..

The motor has enough power so It would work great!

What do ya think?

Sorry to jack the thread, but im guessing these are some of peoples problems as well???

Seems to me that would be a big help. when you consider alot of these vans were running 3.36 3.73s and 4.11s, dropping to a 3.08 or something like that especially running an automatic would make sense.

Oh yeah, this is all starting to sound very familiar.....

donivan65 wrote:I have seen about 10 different variations of the rear mount on a 700r4. And if I ever wanted to cross over to the Automatic side,,,,,it would probably be using a 3rd generation crossmember that I have showing here

Hey Don- Isn't that a TH350 pictured? With a 700R4 that crossmember would have to be installed a different way due to the added lenght.

donivan65 wrote:Transmissions are not going to help,,,,whether they are a 2, 3, 5, or 27 speed, high gear is always 1 to 1, the only exception is if you get an overdrive one, which will drop it down in high gear to about .70 to 1.

Thats why I want a 700R4. Although I am not opposed to changing the rear end as well.

I want to be able to cruise on the highway with decent mileage, for a brick, and without turning a ton of RPM. Also the 700R4 goes with my engine choice...

JC wrote:Would you be able to make another one of those? I would pay you of course.

I dont know many folks with shops in there garage that could help me with this. Plus you obviously already have it done right.

JC- That would be tough without the Van. The frame additions have to be done first then the crossmember needs to be built in the Van with the trans on a trans jack bolted to the engine to get all the angles correct.

Thats ok. I figured I should take donivan65's suggestion anyways. Thats something I could get done since I do know people with welding equipment.

Geez Don...You're just like a girl with her selection of shoes!!! lol JK

Ok now you have confused me with the fake trans mount deal...

Is it still a better Idea to use an actual trans crossmember than to have something made up like Polarbear2's set up?

PolarBear2 wrote:

donivan65 wrote:I have seen about 10 different variations of the rear mount on a 700r4. And if I ever wanted to cross over to the Automatic side,,,,,it would probably be using a 3rd generation crossmember that I have showing here

Hey Don- Isn't that a TH350 pictured? With a 700R4 that crossmember would have to be installed a different way due to the added lenght.

Well that's right, you'd use the hoop if it were a TH350, Duh Mark. I looked into using the 3rd Gen unit, but with the added length of the 700R4 Building what we did was the way to go.

Anyway, I'm glad I've crossed the trans crossmember bridge and you soon will also. Now it's on to, dare I say it,.................the suspension bridge.