GN diff and transmission into 81 Olds

565bbchevy

565bbchevy

Geezer
Aug 8, 2011
6,529
113
Michigan
My 86' Regal project came with a factory 200R4 trans behind a 307 and it has the dual bolt pattern which bolted right up to the 355 SBC I just installed.
I bought a Jegs turbo 400 dual hump crossmember last year when they were on sale for $90 and just installed it and it fit the 200R4 without any issues and I also bought a B&M adjustable lock up kit that I still have to install.
 
ssn696

ssn696

Comic Book Super Hero
Supporting Member
Jul 19, 2009
3,851
113
New Mexico
If the trans, 8.5 and driveshaft go in together, then no issues except the crossmember. If you will keep the 200-4R, invest in an aftermarket dual hump crossmember. You may run into clearance problems if your body mounts have flattened over the years. Poor man's box is a ball print hammer to the floorboard, carpet will cover the dimple. Lockup can be as simple as a pressure switch on the 4th hear test port, looped through the second circuit on the brake light switch, and a toggle or high-beam floor switch to manually unlock. Go here https://gbodyforum.com/threads/200-4r-tc-lockup-kit-build-your-own.58098/ for a wiring diagram and parts list, or fork over $180 for the painless kit and put it in before installing the trans.
 
383_GrandPrix

383_GrandPrix

Master Mechanic
Sep 9, 2016
437
93
Quebec, Canada
are those suppose to be 200-4r transmission's or just representations of chevy and bop?
the reason i ask is i've had 4 200-4r transmission's and all were multi fit bell housings. i have never seen a chevy only 200-4r. but everyone says they exist.
It's just a photo I found on Google to show the difference between the Chev and BOP bellhousings. If the 200-4r's came as dual pattern that's great, it's one less issue for the OP 👍
 
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8

81cutlass

Royal Smart Person
Feb 16, 2009
1,886
113
Western MN
The short version of what you do to make the lockup work is

Replace normally closed pressure switch in 4th gear circuit with normally open so it closes the circuit when it sees pressure
Bring 12 V to brake switch normally closed, open when pressed pedal
Wire 12V to plug on side of trans
Wire 12V through lockup solenoid

Can do the home made lockup for like $20.

A BRF GN turbo buick trans locks up 3rd and 4th gear but everything else does 4th only. I have a chevy 305 2004r behind my turbo buick engine and just eliminated one of the 3rd gear lockup wires in the engine harness.
 
corkatoa

corkatoa

Burger Flipper
Supporting Member
Jul 6, 2013
103
28
Creston, BC, Canada
spend the 250 on a g-force member for an 81, its true dual exhaust member so if you put any kind of HP motor in it later you will want duels anyway.

get a aftermarket lockup wiring kit from CK performance or Bowtie overdrives, locking to TC it will make the trans run cooler and give better MPG in cruse

make sure you use the drive shaft for the GN, its an inch shorter the your stock shaft
I am aware of needing the driveshaft being necessary. Just have to locate it in my vast treasure trove of car parts. Don't know how it can be so well hidden.
I have a dual exhaust sitting (well hanging) around so good advice for sure.
 
corkatoa

corkatoa

Burger Flipper
Supporting Member
Jul 6, 2013
103
28
Creston, BC, Canada
I now understand fully on the lockup issue. Thanks to everyone. I will post pics and explain exactly what goes on.
I looked under the hood for the first time last night with purpose and discovered this:
IMG_0339.JPG

So, TV cable in place.

I will pull transmission out tonight to check but I am sure it has fit-all bolt pattern.

Have until next wednesday to get transmission sorted, then new trailing arms are in and I can put diff in.
 
spidereyes455

spidereyes455

Master Mechanic
Mar 6, 2013
368
63
Northeastern PA
Not that it makes any difference, while I've heard of single pattern 200-4R cases in all my years of messing with these cars I have yet to actually see one.
 

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