700R4 for a 1970 Chevelle [Archive] - Chevelle Tech

: 700R4 for a 1970 Chevelle

Dec 22nd, 09, 4:52 PM
Hi all,

I am looking at buying a used 700R4 out of a 1986 Iroc-z. What things should I look for when buying a used transmission? Any lessons learned from anyone that has done this before?

I believe the only necessary mods are moving the cross member and a different size drive shaft. Other than that a direct bolt on to the bell housing?
1986 iroc-z

the heckler
Dec 22nd, 09, 5:17 PM
always heard to buy one from a 91-up but am sure if you have a quality builder the '86 should be no problem. mine came from a '91 camaro. may want to make sure and get a mechanical speedo drive tail housing (mine came from a truck sans the camaro bosses) for it if it is going in an old car. also get the male plug end from the camaro that plugs in to the trans if you can. that little bugger can be hard to find. I put one in my 67ss this past year and love it. so far it is living just fine behind my 600hp/627 ft-lb 496. I had a real good local builder that used some good parts. from memory - beast h/d sunshell, corvette servo, kevlar bands and stacked clutches. he also recommended a lokar tv kickdown. I use a pheonix trans carb geometry adapter on the 850 dp. you are correct - shorten driveshaft about 3" (measure first) and relocate the crossmember. for lockup I use a dual switch brake light and run only one wire hot to the lockup solenoid thru the switch. I went to the monster transmission website for some great info before I began..I run 3.42 rear gear with 26" tall bfg tires = 70 mph = 2200 rpm...hope this helps...

Dec 22nd, 09, 6:21 PM
The '87 and later have 30 spline input shaft and the auxiliary valve body.


Dec 22nd, 09, 8:10 PM
Make sure to set the TV cable correctly if you want it to live, or you can do like I did and buy A constant pressure valve body from TCI.

Dec 23rd, 09, 12:19 AM
Is that a unique input shaft? What number of splines are on the older 700R4s? Not sure if this is a deal breaker when looking for 700R4s?

Could this problem be fixed by a torque converter with a matching female spline shaft input?

I have an 80s 350 with an after market torque converter (not sure the specs on it).


The '87 and later have 30 spline input shaft and the auxiliary valve body.


Dec 23rd, 09, 1:03 AM
Older 700R4's have a 27 spline input shaft. If you change converter you have to get the correct one otherwise the one that comes out of the Iroc-z will work.

Dec 23rd, 09, 2:27 AM
With the 700r4 the later the better. Lots of improvements along the way. Early ones can upgraded but are usually not worth the effort. Go with at least a 88' or later. Get a good builder to go through it and it will last for a while.