James71Cutlass

What three speed transmissions with an overdrive will bolt up to Rocket 350? I have a rebuilt '73 block with rebuilt '71 heads, 4bbl, headers, duel exhaust and 3:42 gears in the rear end. I know a 200R4 works, but is there another three speed auto with an overdrive. I like to cruise with the car and with this set up my RPM's are just too high when I head out of the city. I picked up a B & M ratchet shifter to go along with a new transmission.

Thanks.

olds 307 and 403

There is the 700R4/4L60E and 4L80E. The 700R4 requires the drive shaft to be shortened and needs just as many strength upgrades as the 2004R. It's gearing isn't as ideal, a noticeable drop from 1 to 2 and not quite as good OD. The 4L80E also requires drive shaft shortening, 1 through 3 the same gears as the TH400 as well as the strength and a so so .75 OD gear. Both transmissions need an about $100 adapter plate to bolt to an Olds V8, the Transdapt is the best. The 2004R fits right in place of the TH350 with the crossmember in the TH400 position. You may need different emergency brake cables, depending on the year of car. The TH2004R has the best gear ratios of nearly any 4 spd. It needs strength/line pressure and servo upgrades. Also an auxiliary cooler, deep pan and bottom feed filter help as well.

James71Cutlass

Thank you for the information.

olds 307 and 403

Also for the "E" transmissions, either a manual valve body set up or an aftermarket controller and TPS set up is needed to make them shift automatically. The 700R4 and 2004R will need this throttle arm bracket on your Qjet. https://www.everyday-performance.com...egory=21060179Also an 80'S TV cable and throttle bracket from a factory Olds 307 with a 2004R car.
https://www.everyday-performance.com...egory=21060179

NTXOlds

If you are made of money, you could also add a GearVendors overdrive unit to a TH350 / TH400 / 700R4, etc. You would need a shorter driveshaft, but it also enables you to "gear split" by engaging the overdrive between gears, effectively doubling your gear ratios. In practicality, I am not sure how easy that would be to use, especially on a drag strip. For everyday driving, there may be situations where it would be okay.

Fun71

I'm guessing when you "head out of the city" you are meaing you drive on higher speed roadways. So what RPM is the engine turning? My car runs in the 2800-3400 RPM range at highway speeds, and it's not an issue for me or the car, even with the AC on in Arizona 110+ summer heat.

One option to decrease highway RPM is to install taller rear tires as that will reduce the overall effective final gear ratio and RPM. It may be an option if you currently have short tires and can change to a taller tire.

RetroRanger

X2 on Kenneths post

Im about 3k at 70 mph. 3:42 w BBO 255-60-15s (27” tall). I had planned on an OD auto trans but the rpms are not an issue. I may do 5 speed manual trans in the future, but thats more about a manual trans than highway rpms.

conversion cost for a OD trans will take a long time to be recouped thru gas savings as well.

James71Cutlass

Yes I am. I currently have 235/60 R15's. I actually need new tires so this might be a good option. Thanks for the suggestion.

James71Cutlass

Thanks for the suggestion.

joe_padavano

Let's back up. There are no "three speed automatic transmissions with overdrive". There are FOUR speed automatic transmissions. The 200-4R is the only one that bolts to an Olds motor. It is the same overall length as a TH350, which makes it an easy swap. The crossmember slides back to the TH400 position. The 700R4 is the only other GM automatic that does not need a computer. It does not bolt to an Olds motor without an adapter plate. The 700R4 is a different length from any other GM trans and thus needs a custom driveshaft. The crossmember also goes in a unique location. Both the 200-4R and the 700R4 need internal modifications to live behind any motor with reasonable output. Arguably the 200-4R has a better set of gear ratios. The 700R4 has a wart of an accumulator boss on the passenger side that can require tunnel mods in some cars.

The 4L80E uses internal parts from a TH400 and is the strongest four speed OD automatic made by GM. It is large, heavy, and requires an adapter plate and a computer.