th400 to 700r4

[zukking01]

I have a th400 in my vehicle with a np208 behind it. I want to know what the changes required will be to go to a 700r4. From what I have found it looks like the 700r4 is 1 inch shorter so I would need to possibly change the driveline length. I know the case has a different spline count so I would need to change cases or shafts. Is there a setup trans and case that will take the place so I dont have to change drivelines or will I have to do something regardless.

What is involved in the 700r4 lockup? Will I crap the trans out if I dont lock it up?

 

[Tacoma]

The lockup is what makes the OD in the 700 worth bothering with. Having just taken my Blazer for a test ride after a few months of sitting, I am once again irritated with my 700. It has never quite been right, and it still isn't.

Since your Bummer is built on a Suburban chassis, get the drivelines out of a 1/2t, 87+ Burb, for cheap. While you're at it, get the NP241 that comes in those trucks and enjoy better oiling and more NP numbers. heh.

 

[zukking01]

So what are you telling me. That I need to buy a 87+ burb for the engine, trans, case and d lines?

 

[DaveB]

You can also find the 700r4/241 case in the full sized blazers of the same years. I got my setup from an 89 Blazer. The 241 gives you a better low range than the 208. I have two 700r4s and three 241s. One of the 241s is for a th400, and one is for the 700r4, and the last one was from a 91 dodge truck. I have swapped the chevy 700r4 input gear into the dodge case to get rid of the output slip yoke. If you need some spare 241 parts I should have some once I am done with my project.

 

[Unimog]

You probably know this already, but make sure the 700r4 from the late 80's era has been rebuilt to current specs before using it. Those early years were notorious for many weaknesses. All can be remedied by replacing internal parts with newer styles.