I made an engine and trans swap recently and noticed that the trans shifts way to early (3000 RPM) at full throttle. What am I missing here were the 75 's electric shift? Is there any way I can fix this ? The only thing I don't have plugged in the trans is the speedo cable as mine runs off the front tire. Thanks

 

Not that it has anything to do with your question, but I'd like to see pics of your JS1.

 

If by "electronic shift" you mean computer controlled, no. That did not start until the 1990s and no TH400s were ever computer controlled. Likely places to look are the vacuum modulator and/or governor.

 

65' Jetstar 1 never restored painted once.An updated pic with it cleaned upic with it cleaned up

 

Check for a vacum leak on the rubber portions of the line to the modulator. I had a bad fitting rubber hose at the modulator on mine. Once I fixed the vaccum leak it shifted just fine,

Nice pictures good looking car

 

You can hook up a kickdown wire with a micro switch (like used for a nitrous system) to get the kickdown working. Just hook to a 12V source.
As far as the way early shifts check the modulater and the governor.

 

Hey that Jetstar looks like the car that Kevin drove in the WONDER YEARS SHOW. His was blue and had the chinese restaurant number decal on the door. Man I am really showing off my age now.

Nice car, what does it have for a mill, 330?

 

Original came with a 425 but now has a 75 455

 

Kevin drove a '65 Cutlass, not a Jetstar 1. All Jetstar 1s came with the 370 hp 425. It was the only engine available on that model.

 

I think the '65 came with a switch-pitch TH400 having two wires going to the transmission. The '75 should only have one connector--for the kickdown/shift speed control. Make sure the correct wire is on that terminal and gets voltage at WOT.
Good luck.
DW

 

Yep u r correct. Kevin couldn't (or his grandpa, where he got it from) afford the Jetstar I.

Switch pitch is better than the 75 TH400 IMO.

 

I believe so, too. Mostly due to the converter.

I prefer the 4-speed of course....

 

I don't beleive it is a switch pitch I think the Starfires got them. It is a factory 3 speed auto. Could it be shifting so early because it is a quart overfilled? Or maybe the screen?

 

Starfire and Jetstar 1 drive trains were identical.

 

The original trans was leaking pretty bad and would not shift @ full throttle unless u let off and hit it again real quick but regular driving it would shift great I actually liked it because I could get a nice rip out of the tires hitting secong very easily with it. Made a couple old R/T's back down I will make sure I have the right wire hooked up. Thanks