Swapping A Th350 For A 700r4?

limeimac97776 · January 31, 2011

Hey folks, I have a 1984 GMC High Sierra with a 350 motor and tranny both from the 1970s. I have a friend who is a ford guy and he has a 1994 Chevy van sitting on his property that has basically rusted away and hes trying to sell it. The van has a 700R4 tranny and a 305 TBI. (I would sell the 305 because i have a 350.) It also has the 12 bolt rear end that my father wants to put in his 1974 Nova because they are better for drag racing. Do you think buying the van for parts is a good investment? And do you think I will be able to use the 700R4 in my truck without buying a new drivetrain? Also, if this was done I would get the gears out of the 10 bolt currently in the Nova so I would have limited slip!

DwayneJ · January 31, 2011

Are you sure it is a 700R4? I thought 94 was the first year they went electronic in the valvebody, I know they did on the cars at least. If it is an electronic valvebody it would be a lot of trouble to swap. I will say I know they were slow to adopt drivetrain changes on the vans so you could be right but double check.

I would expect the axle to be a 30spline 8.5" 10-bolt which is as strong as a old 12-bolt but is not actually a 12-bolt.

limeimac97776 · January 31, 2011

Are you sure it is a 700R4? I thought 94 was the first year they went electronic in the valvebody, I know they did on the cars at least. If it is an electronic valvebody it would be a lot of trouble to swap. I will say I know they were slow to adopt drivetrain changes on the vans so you could be right but double check.

I would expect the axle to be a 30spline 8.5" 10-bolt which is as strong as a old 12-bolt but is not actually a 12-bolt.

Yep. I looked online and they changed to the 4l80E in 1993 with those vans. But I was told that it was not the original motor or transmission in the van. So I will check with him again. I may have to go underneath the van and look at the transmission myself (since he is a ford guy) to see what it is.

ChevyTech77 · January 31, 2011

94 1500 vans will have the 4L60E trans. 2500's will have the 4L80E. Either way, even if you truck is a 2WD you would have to replace the your driveshaft and add a controller to run the transmission. Find yourself a 2WD truck from 84-87. It will have the 700R and proper driveshaft for your application.

limeimac97776 · January 31, 2011

94 1500 vans will have the 4L60E trans. 2500's will have the 4L80E. Either way, even if you truck is a 2WD you would have to replace the your driveshaft and add a controller to run the transmission. Find yourself a 2WD truck from 84-87. It will have the 700R and proper driveshaft for your application.

Yeah your right. Theres always craigslist ads from people parting out an 84-87 truck anyway. I could find a cheap 700R4 there. Thanks for your help.

limeimac97776 · February 10, 2011

94 1500 vans will have the 4L60E trans. 2500's will have the 4L80E. Either way, even if you truck is a 2WD you would have to replace the your driveshaft and add a controller to run the transmission. Find yourself a 2WD truck from 84-87. It will have the 700R and proper driveshaft for your application.

Actually I learned that the van is a 92. So it will have the 700R4 that I need. I can probably just find a driveshaft at the local junkyard that will fit the 700R4.

ChevyTech77 · February 10, 2011

94 1500 vans will have the 4L60E trans. 2500's will have the 4L80E. Either way, even if you truck is a 2WD you would have to replace the your driveshaft and add a controller to run the transmission. Find yourself a 2WD truck from 84-87. It will have the 700R and proper driveshaft for your application.

Actually I learned that the van is a 92. So it will have the 700R4 that I need. I can probably just find a driveshaft at the local junkyard that will fit the 700R4.

Correct, '92 is a 700R4. Make sure that you have the proper throttle cable bracket in place on the engine for the TV cable from the 700R. The TV cable on that trans has to be set correctly or you'll burn it up.

You can probably just have the driveshaft that you already have shortened at an area driveshaft shop, for that swap, for cheap too.