Hello all,
I have a '73 delta 88 with the 350 engine and i think the th400 trans. My problem is that the trans is shifting out of first way late. I don't have a tach in the car, but the rpm's sound way too high. The trans shifts out of the other gears in what seems like the correct time, but first is a problem. I should also mention that it seems to shift a little earlier after the car is warm. My only quantifyable info to pass along is that when cold the trans shifts out of first at around 30 mph, and when warm it shifts out of first at around 25 mph.

Any ideas? What should I check? Is there possible some sort of vacuum line or something that goes from engine to trans that I should check? I really don't know anything about trans, so any help would be great.

Thank you all in advance,
Chris

 

Chris, there is a vacuum modulator on the passenger side of the trans, it is a small canister. You should check/replace it, first check the vacuum, it should be approx. 15 to 20 . If you have a steady vacuum at the modulator, then it is possible your modulator has a pin hole in the diaphragm or the actual modulator valve is sticking. Did you put a new modulator in it, if so, it is adjustable and may simply need an adjustment. The adjustment is located inside the vacuum tube of the modulator. As long as the trans isn't slipping, you should have a fairly simple and inexpensive problem. One other thing to notice is that the governor opposite of the modulator side of the trans should shift you at 22 miles per hour. The governor could be dirty, think about draining the trans and installing a new filter and fluid. gl

69 Cutlass Holiday Coupe
66 Chevy street rod truck
71 Nova 2 door hard top
02 Silverado
91 21' Stingray
85 Kawasaki
84 Kawasaki
02 Yamaha
92 Huffy.....etc.

 

thanks for the comments Cutlass69S. I have been crazy busy lately, so I was hoping to wait a while before I dig into this, but the trans is shifting even a few mph later now, so I will give your suggestions a try as soon as I can. One question, what do you mean by the trans slipping?

Thanks,
Chris

 

THANK YOU CUTLASS69S!!!! That is exactly what the problem was. I got underneath the car to take a look at vacuum modulator, and the vacuum hose connected to the mudulator had a huge split in it. I replaced the hose with one I had in the garage, and problem fixed! Once again this site has given me the answer to my problem. Thanks !!!!