moonframer

My 1956 powerglide (original) wants to slip every now and then when shifting from 1st to 2nd. It almost always does it when the car is cold and I'm going up a fairly steep hill when leaving my home. If I let up on the accelerator a bit it seems to shift into 2nd. Seems to downshift fine... I was told two things: possibly a modulator problem or bands that need adjusted or replaced. The fluid looks nice and red and it is to the correct level. Any ideas?? Thanks Jim

KENS78SILVERANNIV

I was built in '56 too... and I'm beginning to slip a little too. . Awesome that you have the original trans. You know what to do.

ohiovet

My rebuilt 57 cast iron PG sometimes does the same thing.
Could be band adjustment or improperly adjusted kick down linkage.
The 56 and 57 Corvette PG trans does not have a modulator although the passenger cars have one.
How does it shift from 1st to 2nd if you use the shifter?

moonframer

When I shift manually, it shifts fine.

moonframer

As a matter of fact, now that you mention it, the kick down adjustment is set up wrong because it won't kick down into 1st gear unless you use the shifter. I was going to look into how to adjust it so it works properly. thx

ohiovet

Adjustment instructions are in the ST12 I think.
Be very careful as if it is adjusted wrong it will screw up (RUIN) the transmission.

moonframer

thanks. will give it a shot.

ohiovet

Tell us how it works out.
Thanks,
Bruce B

Kyle'56

Moonframer,
I hope that its just the kick down linkage, but i don't think it is. I own a 56 too (but a manual). If it were me I would see how long its been since the transmission was rebuilt. If it hasn't, then its time. It seems more like its time to rebuild and get it taken care of. Its an investment that no one wants to pay out. But with the automatic, if its slipping, its on its way out. If you see something that doesn't look right take a picture and post it. If you have any other questions i would be glad to help out.
-Kyle

moonframer

Hi Kyle, Thanks for you advice. I think you may be right! It probably needs rebuilt.I will do some homework on a reliable shop in my town.

I do have another 1956 question. No one seems to really know what the spark plug wire heat shielding looks like on the 56. The long polished horizontal shields that mount over the plugs on a 57 and later model don't seem to fit the 56. I think that the 56 got the light weight shields, two on each side or four total. Then there looks like wire shields that bolt to the block. The distributor shield appears to be different than the 57 and newer too. Any ideas.. Thanks Jim

Kyle'56

Moonframer-
Sorry for the delayed response. The ignition/spark plug shielding on the '56 are different than that of the '57. In '57 the configuration switched to include lower mounted shields. This means the the vertical shield would have a different fit to accommodate the application of these lower shields. So in '57 you has the top, R L vertical, and R L lower shields. In '56 you had the top and the R L vertical shields.

Here's a link to an accurate '56 configuration:
http://keenparts.com/pages/Catalog3.php?diagram=2704

Do take note the it is a bolt that goes into the top ignition shield. The wing nut appears in '57. There have been cases where late late models of the '56 had a wing nut because of the factory switching over to the new production. But you'd have to be sure of it. Otherwise it is a bolt.

Also I can help but notice that site will try to sell complete packages but for the '56 you will not need most of the parts nor should anyone just try to cram it in the engine compartment. I've seen this done.

What specifically are you looking at in regards to wiring?

As far as the distributor is concerned the top ignition shield covers it. As the models progressed and the c2s came out they still had shield but the shield contained a cover so you could unfasten the cover and not have to disassemble the whole shield unit to check or work on a part. Makes life easier. But fortunately and unfortunately we have a much more primitive car. But this adds to the fun. Its a never ending process of learning and find out new things. They most certainly had many things that are not found in manuals and troublesome. Let this be known, they will have parts from the factory that do not appear correct. For example my '56 is a late model year production and I have a top that came from the factory that was going on the '57. They were starting to convert. Guys on the assembly line would grab parts that they needed and sometimes it would be a newer part than it was supposed to be. hues of wiring colors can be a little different. a bracket, screw or nut. So really get to know your car, where and when it rolled off the floor. Youll find out some amazing things.

Best of luck!

-Kyle

moonframer

Thanks for the response Kyle.
I have been in the Corvette hobby for nearly 50 years and have enjoyed learning about these wonderful old cars. My car is no. 1426. So it is almost half way through production. I had mentioned that this heat shielding issue is a bit unusual. This is a light gauge metal shielding that is mounted between the plugs and manifolds. In early 1956 the factory installed a four piece shield that is different than the 57 models, that is one piece on each side. Possibly,the 55 models had the same 4 piece shields since they were also 265 cu.inch engines.
I spoke to some extremely knowledgeable straight axle guys that agreed
that these shields are not reproduced and hard to find.I do have the original brackets still mounted to the block.I am optimistic that someone has a set they don't need. My search goes on. Jim