Transmission? Problem

[Donald M.]

Today, I went in for the final test drive before shipping my '54 Corvette home. It is now running like a champ, rides great for a 62 year old car, and steers like it is on rails with its new rack & pinion system.

While stopped to check my map, by chance I pulled away from the stop with my steering turned slightly from straight ahead. My application of throttle was not brisk; neither was it subdued. The car started lurching as if it was shifting in and out of low range. It was quite violent. This does not happen when pointed straight ahead brisk with application of throttle, nor does it happen with subdued throttle when steering not straight ahead.

My mechanic thinks this a problem with the modulator? or the kick down mechanism. Does anyone have any experience with this?

Don Moses
Bayview, TX

update: Shop just called. They now think the problem is inside the transmission. Some tests were run that should have softened the L to D shift, but resulted in no change; still a hard abrupt shift. Still hoping someone knows something about this.

[Mark E.]

Re: Transmission? Problem

Many years ago I had a 65 Impala with a PG. I learned the vacuum modulator affected shift firmness, while the throttle valve affected shift rpm points and kick down. Im not sure if a 50s Corvette PG is similar, but with your symptoms, check the modulator and vacuum lines. Leaks? Ruptured diaphragm?

After that it may be worthwhile going through the valve body before deciding a complete teardown is needed.

[Donald M.]

Re: Transmission? Problem

Mark,
Thanks for the reply. Transmission gurus think they have the problem isolated in the linkage to the carbs. My transmission is shifting out of low way too early; almost immediately upon application of any throttle. Trans guys are now trying to play with this linkage to change the shift point before they tear into the transmission. Is this what you referred to?
Don

Many years ago I had a 65 Impala with a PG. I learned the vacuum modulator affected shift firmness, while the throttle valve affected shift rpm points and kick down. Im not sure if a 50s Corvette PG is similar, but with your symptoms, check the modulator and vacuum lines. Leaks? Ruptured diaphragm?

After that it may be worthwhile going through the valve body before deciding a complete teardown is needed.

[Donald M.]

Re: Transmission? Problem

My transmission problem is solved. (knock on wood) A gentleman by the name of Lawrence Vaughn in the Dallas/Fort Worth area is going to rebuild the transmission. He is an older fellow, known by my restoration shop, who when asked how many powerglides he had worked on replied, "Oh, around 200 or so."

Time will tell if this was the right decision, but at least for the time being I am happy and optimistic.

Don

[Troy P.]

Re: Transmission? Problem

If you have a problem with adjustment of the kick down linkage a rebuild won't solve it. But it may take care of other parts of the problems you described.

[Mike M.]

Re: Transmission? Problem

i had similar problems with a 57 250 hp PG. i had the local trans shop rebuild it twice(the owner is a good friend and is very well versed on the 62 up aluminum power glides but he was unsuccessful in rebuilding the original cast iron PG in the old 57. after the 2nd attempt to fix it, the tranny grenades internally--terrible noises and total failure to move. i ended up taking the PG to Fatsco's in no new jersey. their old-timer was very familiar with the cast iron variety and rebuilt it. salty fee. nonetheless, it breezed right thru its PV about 8 years ago, and hasn't failed yet. and no puking of aft after sitting a few days. Fatsco has my admiration. have yours rebuilt. mike

[Donald M.]

Re: Transmission? Problem

I was a bit cryptic in my previous post. The transmission shop who did recent adjustment work on the carb to throttle valve linkage got the transmission where it would shift L to D around 25 mph, and would kick down around same speed. On coasting to a stop the trans would drop down on its own around 10-15 mph. This seemed to be problem solved. The almost instantaneous L to D shift was gone, along with the violent chattering caused by this very early upshift.

Two days ago the shop took the car out for a test drive. All seemed well, but on the way back to the shop the car would not stay in gear. Any attempt to increase speed much beyond idle would result in the transmission dropping out of gear. This has never happened before. Every trouble shooting guide I can find suggests this is related to band adjustment or worn clutch plates. In any case it is now necessary to remove the transmission to investigate. Since the transmission is coming out, I have decided it would be foolish not to go ahead and rebuild the transmission since the current problem seems to indicate this is needed. Time will tell. I don't know what else to do.

Don

[Donald M.]

Re: Transmission? Problem

I looked up Fatsco's website. They have a master rebuild kit specifically for the '54 Corvette, and have other parts as needed. I'm going to suggest Fatsco parts be used for the rebuild.

Don

i had similar problems with a 57 250 hp PG. i had the local trans shop rebuild it twice(the owner is a good friend and is very well versed on the 62 up aluminum power glides but he was unsuccessful in rebuilding the original cast iron PG in the old 57. after the 2nd attempt to fix it, the tranny grenades internally--terrible noises and total failure to move. i ended up taking the PG to Fatsco's in no new jersey. their old-timer was very familiar with the cast iron variety and rebuilt it. salty fee. nonetheless, it breezed right thru its PV about 8 years ago, and hasn't failed yet. and no puking of aft after sitting a few days. Fatsco has my admiration. have yours rebuilt. mike