cutsupreme72

Hello all,

You are my #1 source for researching some harebrained Idea I'm working on in my head and let me tell you thus far my car projects have been perfect and worked out in every way thanks to all of your knowledge and input. I've had my car about 2 yrs. and love it like part of the family, but even that needs counseling every now and then too! Here's what I got, what I hope to achieve and I wanted to see your thoughts before I dove into it full force.

I have:
72 Cutlass Supreme
350, 4bbl, edelbrock intake, headers, HEI, basically a cruiser TH350 trans.
2.73 gear ratio (10 bolt rear end) I believe 8.2? it's scalloped on the rear diff cover.
I have the 4 speed conversion already done on the stock floor shifter, new cable detent, etc. so it's ready to go in when I decide time $ is right.
255/60/15 rear tires on 15" weld rodlites. 50 series on the front.

Currently I'm about 2300 or so RPM @60mph 3000 or so at 75mph. These are just what I remember if you need exact figures I can always take her out for a cruise and get you exact figures.


I am researching:
200r4 conversion. Have my eyes on a built 200r4 billet servo, clutches, bands, reinforced, etc. Guy basically has a built one but found a sweet deal on an LS swap. so went that direction and is now looking to sell pretty cheap.

I am wondering with the 200r4 will the 2.73 gears work or will it be a messed up ratio and look like my horse is bucking going down the freeway? Mind you I know nothing about gear ratios and transmissions with more than 1 speed (I'm a boat guy Fwd or back) with a rear end underneath the water so consider me to have no knowledge on the subject when replying.

I know I'll have to do a lockup, not a biggie there, plan on doing a switch out of 4th gear plug, that connects the gnd. at the connector on the drivers side. That way She'll lockup in 4th. (let me know if there's a better way.) not looking for toggle, etc. just for it to be hassle free.

I'm aware of the cross member and parking brake cables,

What I'm really interested in is gear ratio vs. transmission. (will I have to have gears changed) and at that point do I throw a posi kit at it? What's the best gear ratio for this setup? I do cruise street, more hwy though. I want a car I can cruise comfortably on the street, but not feel like I'm 10 RPM from having the engine jump out of the engine bay while stomping it on the FWY. (i've always had OD cars) so I anticipate that shift down and smooth cruise @60-75 that never comes. I've heard this conversion makes it nicer. If I get a few MPG's great, This car will never pull Hybrid MPG I drive it to enjoy it so i'm not trying to reinvent the wheel here. Any help would be greatly appreciated! Mainly gear ratios, experiences, etc.

Fun71

I can't help with a lot of your questions, but the rear in your car should be an 8.5" 10 bolt but of course it could have been swapped any time over the past 40+ years. Many folks misidentify these rears as an 8.2" 10 bolt based on those scallops.

70vert

As far as gearing goes look at it this way. Other than the 442,Monte Carlo ss and the grand national all the other cars in the 80s with the 200-4 had ratios in the same ball park you have now and they drove just fine. Granted they were made for economy but it doesn't sound like you want to go scorching down the drag strip anyway.

cutsupreme72

Thanks guys, good info. I keep looking around and people are saying the gears on the 200r4 will never work with 2.73 gears and the car will take a while to get thru certain gears,etc. bucking on the highway, etc. Again all of this I know nothing about!
I would just hate to put it in there and have an undriveable rig. But if I can get it in there and come up with a good street/highway gear setup later I'd be really thrilled. I'm anticipating the cost of the trans, install and the other 8 things I left out and other items my OCD won't let me live with while under there and I'm sure the cost of rear end gears/work will add up quick. So if I can do one, give it a few months then do the next I would be a happy camper!

Fun71

I have read that the plain Jane Cutlass with 307 engine had a TH200-4R overdrive trans with a 2.41 rear, so your car with more power/torque and 2.73 gears would do much better.

I don't agree with the "take a while to get through certain gears" as the TH200-4R has a much lower first gear than the TH350, a very slightly lower 2nd gear, and the same 3rd gear, so overall t will "go through the gears" faster than a TH350.

bccan

Red car has 350, 300ish hp, stock BRF w/ CK Shift kit 200-4R, 3.08, 27ish tire, turns appx 1800 @ 60mph locked up. Runs nice & smooth on highway, no lugging or bucking.


It used to drop into OD around town (30-35 mph or so @ light throttle), no driving complaints. 2 years ago for some unknown reason it spontaneously doesn't want to drop until highway speed, don't know why & couldn't figure it out even after dropping valve body. So it remains to this day.

cutsupreme72

This sounds like the ticket to me then. I was just curious as to the gearing needed on this setup but sounds like you guys have either seen or had something close to what I have. I would like a post rear end with a little snappier gearing in he future but if I can get the tranny in, and still enjoy cruising without having to lay her up for a long period of time I can do these projects and still enjoy the car. As always Thank you so much for all of your help! I work on boats by trade but am a locomotive electrician in my current craft so if you ever need tips on a boat or happen to be shopping for a locomotive I'm your guy Laughs! Have a great week!

cwracer

I ran cross country in a vista cruiser with a 200R4, 2.73s with a 350 rocket. Ran great, just idled down the freeway at 80. Does need to downshift with any grade though.

olds 307 and 403

I ran 2.56 gears with my 2004R and a mild 403. I run at 1850 rpm at 60 mph, 3.42 gears and 25" tall tires with the converter locked up.

olds 307 and 403

Red car has 350, 300ish hp, stock BRF w/ CK Shift kit 200-4R, 3.08, 27ish tire, turns appx 1800 @ 60mph locked up.
That sounds high for that gearing, my speed is bang on according to my GPS.

cutsupreme72

Thanks cwracer, glad to hear someone had good results with the same setup I have. Now just need to get my hands on the tranny, missed a great deal due to my night shift schedule, you snooze ya loose, in my case not much snooze but a definite lose! Thanks again for the great advice! You guys are the best!