brianbeez67

67 Cutlass Supreme, Gonna be fresh engine rebuild along with cleaned up stock 3.08 rear end
The transmission has been sitting for over 30 years, my thoughts are to replace all fluid, new filter, new front and rear seal
and run it. It ran fine prior to sitting. Should I give it a try or my other thought is just replace it with TH350? (I Don’t have)
thanks in advance

danktx

You need to replace all the seals. When I had a Jetaway in mine it should have been called a sieve. It leaked from every seam and orifice. I have a T350 that was in a 69 Cutlass if your close.

matt69olds

You have already spent some money going thru the engine and rearend. Dont handicap it with a lame transmission.

A th350 is a easy swap. However, since your starting from scratch, a 2004R would be even better

brianbeez67

Well, the 200R (I just looked up seems to much for me to purchase now, maybe in the future). I did some research with the help of 69 CSHC and have the switch pitch at max 2450 stall without switch pitch it lists 1950 stall (Motor Trend July 68). So with that in mind
1. What stall converter would work?
2. What is the first gear ratio of the trans

I have my sights on TH 350 in my area and want to know what you guys have for suggestions?

joe_padavano

The ST300 has a 1.76:1 first gear and 1:1 second gear. The TH350 is nearly a direct bolt-in. The only issue is connecting the kickdown cable.

brianbeez67

Joe, you said two things that got my attention
1. Nearly a direct bolt in- what extra things will need to be done
2. Connecting the kick down cable- how so

thanks Brian

oldcutlass

The easiest way for a kickdown cable is going the Chevy route, you need a cable, bracket, and the slider stud to adapt the carb linkage.

joe_padavano

This is about the easiest trans swap there is. The ST300 and TH350 are the same external length (assuming you get a short-tail TH350), use the same mounting points, and use the same driveshaft. Shifter linkage bolts right up (though if you have a floor shifter you'll need the trans bracket that holds the cable to fit the TH350 pan). Trans cooler lines bolt up with possibly minor bending. As I noted, the big difference is the kickdown cable on the TH350. On a 67-earlier car, the easiest way to do this is to get the kickdown cable bracket from a late-70s Olds that bolts to the Qjet rear mounting bolts and fabricate an attachment on the carb throttle arm to connect the cable. Second choice is an aftermarket cable kit, but those will all come with brackets designed to bolt to an SBC, so some bracket fab will be required. Other than getting the correct speedo driven gear for your car, that's all there is to it.

matt69olds

Technically, a TH350 will work and shift without the kickdown cable connected. Unlike a trans with a throttle valve, the only thing the kickdown cable does on a 350 is force a downshift at full throttle. It has zero effect on line pressure. Try that with a trans using a TV cable, the transmission lifespan will be measured in feet.

The only issue with using a TH350 with no kickdown cable is obviously no full throttle downshifts, and it will always “short shift” at full throttle. Meaning the WOT shift points will never be much more than about 4000ish.

Kickdown cable adjustment isn’t really critical on a 350 trans. As long as the cable travel maxes out around WOT, it will work fine.

I would think it would be pretty easy to fab up a kickdown cable mount using a throttle cable/TV cable carb bracket from a late model 307 engine.

If you really don’t want to mess with the kickdown cable and don’t mind pulling the shifter into 2nd when you need the passing gear, you can easily modify the kickdown linkage in the pan. If your interested I can post a YouTube link detailing the process.

69CSHC

Brian I believe you want more giddy up. With your stock cam and 3.08 rear I would do the TH350 and go with a 2000 to no higher than a 2500 stall converter. A 1967 Cutlass Supreme 320 HP 330 comes with a nice camshaft from the factory. What is hurting your factory performance is the 2speed, your starting line ratio (transmissions 1st gear multiplied by the rear gear) is horrendous. Its a 5.42 , with a TH350 and its 2.52 1st gear it would be 7.76. A TH350 version would destroy a 2speed version switch pitch or not in a race. Performance cars from our era ideally want a starting line ratio anywhere from 9-11. As you can see your stock setup is half of the high end of that. The high stall of the switch pitch helps but can never make up for essentially not having a "real" first gear.

matt69olds

The Jetaway trans has a first gear ratio of 1.76. The 2nd gear ratio of a th350 is 1.52

Huge difference in get up and go, with zero trade off on highway driving.

brianbeez67

Found this pic on a thread a few years old, 67 Cutlass 2 speed jetaway switch pitch. The one on the left with the weld spots they said was a switch pitch, then what would the one on the right side be? Pulled mine yesterday and it looks like the right side converter. My trans was replaced before I bought it, it had yellow pen on the converter that said 66 Cutlass. Would that be the difference?