Sorry, I know this info is out there, but I haven't been able to relocate it on a search. I have a 342 posi rear end and am pulling 3400-3500 rpms at 60 mph. I want to put a 200-4R in it this spring to lower the rpms so I can cruise at 70-80 on the highway. Can someone please tell me what I can expect my rpms to be after the swap at 60 mph, 70 mph, and 80mph or tell me how to figure it out? Depending on what those numbers are I might switch rear gears too. I'm past racing from stoplight to stoplight, but I want the car to be able to get out its own way yet still be very highway friendly.
Thanks,
Mark

 

Will also need the tire size you are running.

 

Your tact may be off. I have 3.91 gears,and don't run the high at 60MPH. But I also have 15 inch tires.

 

lshlsh2 I'll have to check this weekend. The car is in storage. I believe they're on the larger side as they fill out the wheel well very nicely.
Thanks

 

442Harv I know my tires are bigger than 15". My wheels are 15".

 

Mark, unless you're running wheels off an old Mini-Cooper, those numbers are way high.

 

ThirdTry Yeah, I know. It's insane. That's why I want the new trans.

 

It's OD ratio is .67 to 1 instead of 1 to 1, so your car, with nothing changed, will have 2/3rds the indicated rpm in the new OD from the current drive.

Please understand, what people are trying to tell you is that it's not your transmission that has an issue unless you are stuck in second; it's your tach. First step for you is to confirm you shift into all gears. Second step is to confirm your RPM in top gear at various speeds. Running a 26 inch tire in drive with a 3.42 gets 3500 at 80, not 60. Your tach is 25% off assuming you have a normal height tire.

 

Koda thanks. I get that this could be the issue (probably is), but I still want to get the 200-4r for the highway. But back to the tach... What would cause it to be so off and how do I trouble shoot it? Since it's the tic-tock tach and the clock only works intermittently, would a short of some sort throw off the tach?
Thanks,
Mark

 

Factory tic-tach or repop? In either case, they're none too reliable. Hook up a reliable unit and get an accurate reading to confirm.

BTW, another way to tell: is the engine making a hell of a racket @ 60 MPH?

 

My tach is off like yours. There's an adjustment screw. You could pull your tach and send it to red line gauges and they could fix the clock and the calibration. They aren't that accurate to begin with. The screw is very finnicky and takes fine adjustment and a little does a lot. One can move screw, reinstall, test, and repeat. Some wild men have hooked the tach up outside the gauge cluster with extensions, but the gauge pod is the ground and you can ride the 12V if you're not careful.

 

ThirdTry I have 2.5" exhaust and Dynomax 2 chamber mufflers. I can barely hear the engine LOL.

 

Koda I don't know if messing with the screw is worth it. I still wouldn't know if it was accurate unless I had another tach hooked up to compare it to. I might just look into red line. Depending on the cost, it might be worth it. Thanks!

 

lshlsh2 I'm not sure if you've been following all this, but I'll still get you the tire size this weekend.

 

Our speedometers can be extremely off due to old age. Some are born off from the get go, and get much worse over time ...

If this is the car/wheel combo in question. Tires look huge, like 255 60 15s which are 27 inches tall.



If your car is a th350 combo, 3500 rpm is 78 mph with 255 60 15s. In turn, 60 mph would be 2700 rpm. If the transmission is stuck in 2nd then it's turning 4100 rpm at 60 mph. Give or take.

 

As mentioned, before doing anything, make sure the transmission is shifting into all three gears.

The factory tachs are not very accurate. I’d temporarily install a aftermarket tach and take the car for a drive. You might be pleasantly surprised.

To answer your question: depending on tire size, I would expect cruise rpm yo be around 2200-2400 at 80 with the converter locked. An added bonus, overdrive transmissions have a lower first gear meaning more get up and go at the stoplights. Win-Win!!

The biggest flaw with the 200R4 is they aren’t very strong. At the minimum, install a trans-go or CK performance valve body kit. Make sure the TV cable is set up correctly, “close enough” will result in a burnt up transmission very quickly.

I wouldn’t hesitate to use a 200R4 behind a small block. If you have a 455, I’d consider some upgrades. The forward clutch housing is a known weakness, it will snap off without warning. When that happens, you have seven neutral gears and park. The upgraded part is expensive, but a tow bill and later repair will be even more expensive. Buy once, cry once.

 

I too had a 350 4 bbl th350 set up on my 75 cutlass with 235x70 x15 tires.
I decided to change the gearing to 3:42 posi with the same tires and th350 tranny.
The car rev’d a lot more than I liked at 65 mph.
it felt like was stuck in 2nd from the original gears.
so I decided to change the transmission out to a rebuilt 200-4r with automatic lock up.
All I can say, tires will bark real nice with the shift and cruise very nicely at 70 mph
i have since out on new tires and put 255x70x15 on the rear.
Very happy with the set up. I don’t go to the track with it. It can spin the tires nicely doing a brake stand.
Very important like previous posters said about tv cable adjustment.

 

I don't see that anybody has mentioned the plastic speedometer drive gear in the transmission. The wrong gear can cause the speedometer to be way off. Is it the gear for the 3.42 gears.

 

That's a good point. Confirm speed with GPS.

 

http://www.wallaceracing.com/gear-speed-calc.php

 

For those numbers to be accurate, your rear tires would be 20" tall. A 27" tall tire would be 2650ish at 60. You must have forgot to carry the one or something.

 

69CSHC Thanks Phil, that's the info I'm looking for. Yeah, the tires are big and meaty. I know the few times I've stomped on it, it was all 3 gears, but the way everyone keeps bringing it up, you all got me second guessing now. I'm going to say it does, but this spring I'll definitely make sure.

 

matt69olds Thanks Matt. It's a 350 and I did the 200-4R in a '71 I used to have, it was fine. There's a really highly recommended trans shop just over the border in WI that I'm going to take it to. Right on their website they say "ask us about our 200-4r trans for your classic" or something like that.

 

Tuffnut

 

redoldsman I was not aware of that, so I'll ask either the trans shop or my mechanic to look at it. Thanks

 

Qwik71442 Very cool, thanks!

 

Get to cruise and shift manually to second. Something will happen obviously, or it won't.

 

This may be comparing apples to oranges but here goes. As of 2003 I now have a 200r4 in my blue 79 Cutlass and with 3:08's I'm running 1850 rpms (or so that's what my factory tach is reading) with 205-75-14 radials. Before I blew up my M200 (3 speed) it was running 3,100 with the same size tires. Not good. I had another 200r4 built for me last year by Extreme Automatics in Ohio and I am completely happy with how it is doing. IMHO you will really enjoy the OD as your motor will not be winding up so high; makes the car entirely more drive-able at modern highway speeds.

 

Are you sure you have 3.42s? Those RPMs you're turning are close to my 3.91s with 225/70/14 BFGs. Also, you can download one of the few phone apps to check your speedo. I've used Ulysses Speedometer in the past.

 

BlueCalais79 Yep, I had one in my 71 and like it better on the highway.

 

Az697175 I know, right? In the folder with parts docs is a hand written note from one owner to the other that it's a 3.42 so that's what I'm basing this all on. Spring really can't come quick enough so I can get this all sorted out. If I can't find a stamping on the dif cover, I'll count driveshaft revolutions as I spin the wheels. One way or another I'll get it all sorted before the season really kicks off.

 

You're on the right road there, with the driver cars you want drivability for sure. My blue 79 has enough drivability changes/upgrades that when I enter the car in the Nats I feel compelled to put it in the Modified Class, which I have done.

"Your Car, Your Call."

 

This calculator is accurate with the torque converter locked up.
http://tech.oldsgmail.com/ch_axle.php
I find the 2004R drops rpm around 1000 rpm at 60 mph with the torque converter locked up. Hopefully the shop really knows the 2004R and builds plenty of them.

 

👍that's the ticket. Along with https://www.tirerack.com/content/tir...s&gad_source=1 for specs. Those are my automatic go to's.

Blue my brother had a mint burgundy 79 coupe with the 260 cid. He was absolutely not a lead foot, he is a potential car buyers dream owner. Babies cars to the point of cleaning rims with a toothbrush to get in the nooks and crannies. Would avoid washing the car in direct sunshine. Would wash at night to avoid water marks, etc. While being meticulous with maintenance. The metric 200 went on him twice back in the late 1980s. It was a low mileage unabused car. At the time the mechanics all told him the same thing, the transmission was absolute trash.

By my estimation the worst transmission to come from GM the last 60 years.

On the other hand the th200-4R is solid. Have had it in a few G bodies. Absolutely kick *** in my 87 442. And the entire world knows it was kick *** in the GNX. Metricmetal I concur with Blue, definitely a good way to go. And if you are an easy going driver your car gets to go to sleep on the highway like most new cars do...

 

Couldn't say it any better, well summed up 69CSHC, With this 200R4 mated up to my 260, the car will be riding off into the sunset long after I do.

 

Problem is, he's not running a 260. A near stock 2004R won't last, gone through 4 of them with my weak junk Olds 350's and 403’s. The TH200 was an instant removal when any issues, including leaks in the shop I apprenticed at 25 years ago. He may have lost 3rd, I lost that on my last TH350, which would explain the rpm. I am not sorry going 4L80E just for it's strength and finally something that doesn't leak.

 

That's for sure, I forgot about the leaks, that issue seemed endless when that M200 was in the car. I'm glad that's overwith.

 

I had leaks, usually the speedometer, selector shaft seal and torque converter and tail shaft and pans on TH350's ,minor but always there somewhat. I think I had one TH2004R that didn't really leak. All the rest leaked somewhere, including a Hughes deep pan, I should thrown out, others had issues as well with that pan. Probably bushings needed replace on the pump and at the tail shaft, not so easy on a 2004R. I may have seepage at the torque converter seal, replaced the tail shaft seal for minor leakage, has a fancy dust boot, even it is expensive on a 4L80E. If his 350 is stock, then a stock 2004R rebuild with bigger boost valves, hardened stator and deep pan with bottom feed filter may be enough. You need 200+ psi in foward gears to get firm shifts. I got one, added the .555" boost valve, 215 psi with full TV. Stock part throttle shifts and very firm but not harsh full throttle. You will need the governor modified to get more than 4000 rpm WOT. The small weight needs shaved and should be staked to increase rpm. I got 5000+ rpm shifts doing this. Also I find stock non high stall TH2004R converters stall about 300 rpm high than the stock TH350 converter, 1900 rpm vs about 1600 rpm. That with the better first gear will launch the car nicely and run about 1750 rpm at 60 mph with his tire size and 3.42 gear. I really liked 3.42 gears with a 2004R, best of both worlds.

 

I wouldn’t hesitate to use a good used 200r4 behind a mild small block, they aren’t nearly as weak as people think. Put a CK performance or TransGo shift kit in it, and make absolutely sure the tv cable is right.

Obviously, if it’s being rebuilt, some durability upgrades are preferred.

 

matt69olds I agree 100%. While I appreciate everyone's input on the durability of the 200-4r, I've done plenty of research and they're a good trans. Yes, way back in the day, they were weak, but those issues were fixed and if one goes to a good reputable shop they'll be fine. I have a 350, no history on whether it has been cammed, but it doesn't seem like it. My neighbor is a retired mechanic and used to build drag cars. While it isn't his first choice, he too said for everyday driving it's fine.