[Skip Fix]

I know some guys will only use cores form a Monte SS or GN.

Steve C has one behind his 505!

[76TA462]

I picked up a 2004R stage 2 non-lock-up with 9.5" 2500 stall from Extreme Automatics in 2020. Behind an approx. 600 hp tq (at crank) 455 in a Trans Am. Chose it over the 700 over becuase I liked the gearing better (for me). Bolted right in and the Holley TV cable they supplied worked with the excellent instructions. Not a single problem for me. Been flawless and a ton of fun. Not tracked but lots of fun street stuff. Extreme Auto gave great advice. And have parts too, if you build up your own (they did at the time). There are several good places, but this worked for me. For what it is worth.

[76TA462]

Forgot to mention. The Extreme Automatics uses a GN styled valve body they manufacture. It can be bought but I believe they need your valve body and related parts in exchange as well.

[Steve C.]

A tidbit for conversation, not necessarily a recommendation here.....

I personally found the cam choice had a factor in the converter used.

At first I used a lock up converter from the source I bought my 200-4R transmission from, but I didn't like it.
At the time it. was a 650 hp combo with peak power at around 6000 rpm, and peak torque at 4900 rpm.
It was a solid roller with 255 degrees intake duration at .050".

With that cam the engine with the lock up converter gave a feeling from what I read is commonly called a chuggle. This chuggle or slight bucking that I felt in OD was from the converter locked at slower engine speeds driving around town. Sort of similar to a manual transmission lugging in 4th gear at a slow speed.

Soon after I changed to a non-lock up converter. Under a steady state cruise speed on the open highway this converter has about a 200 rpm slippage, very acceptable in my opinion.
With my 27.7" diameter rear tire and 3.73 gears it is about 2300 rpm at 70 mph.

I know other have no issues with a lock up converter and a 'big' cam, but again I did not like it.


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[71 Goatman]

Originally Posted by cdnturboz

Yeah overall for what I’m doing (no track days) I figured it would be fine, mostly just curious if I should wait and find a better Monte SS or GN trans, or if the internals of this cutlass one can be somewhat upgraded to be similar

Have had an Extreme Automatics 200r4 in my 71 GTO since 2009, no issues whatsoever. Solid built trans you can beat to death.

[Willz428]

AGREED

[KSZR]

I've got a 2004R behind the big valve 400 in my Lemans. The extra gear is nice and low gear is lower than the 350/400. It came out of a Caprice wagon, similar year.

Bolts right up to the Pontiac block no adaptor required. Same length as the T350 and same shaft so that was easy on my car.

I had it rebuilt with a shift kit. Biggest challenge was getting the governor setup correctly for shifting at the correct rpms wide open. Had to drop the pan several times to grind the gov weights.

What I have seen it is fine for 400hp.