Drove my 1977 L48 today for the first time since I bought in 96 degree temps and started to have shifting problems after about 15 minutes of driving. I have only owned the car for about 9 weeks and this is the first time I drove in temps above 85 degrees outside.

It generally shifts like it has a shift enhancer installed. It shifts hard 1st to 2nd then lighter 2nd to 3rd under normal acceleration then really shifts hard in all gears when I really pound on the gas and shift beyond 3000 rpms.

Today it was stumbling or maybe even slipping when going from 2nd to 3rd once I got close to home on my way home from work which is a 12 mile drive. It has acted normal in the past even with a 75 mile trip in cooler temps but the engine would get hot until I put a dual stage 160 Degree thermostat in it. This helped to cool the engine down.

The engine temps got a little warm even with the new thermostat which a tranny can cause if it needs a rebuild from my past experience with a 1976 Malibu Classic.

This car sat for almost an entire year before I bought it previous owner only put 1000 miles on it so wondering if the clutches could have dried and cracked from sitting too long than causing extra friction and causing this problem.

Thinking I need to take it in to Tranny shop for an inspection. Going to buy an extra 2 quart capacity finned pan before I bring it in to the shop. If I need repairs I am going to buy extra parts. Replacement pans have drains in them so I want draining pan so in the future the tranning can be drained before maintenance.

Want second opinion from anyone else that may have had this problem.

 

check the fluid? btw where'd you get the two stage t-stat?