66 gto problem

[thatguy101]

i bought a gto new in 66, over the past few years it has started having a problem where when u hit the gas when drivin down the road it starts to bog down and won't go into passing gear. It does ok when u first start it up and drive it but when it gets heated up u won't be able to hit the gas or it will choke out. It leaks tranny fluid and i think it may be the transmisson but not for sure. Can anyone help?

[MrPbody]

Sounds like multiple problems. When was it last fully serviced? Trans fluid changed? Tune up? Carb rebuild? Lots going on here. 4-bbl or TriPower?

Provide as much info as possible. May be time for a trip to a classic car specialist for a MAJOR tune and service. Could also need a trans overhaul. Not unusual for a 42 year old car... When talking to them (trans shop), make sure they know it is a "Super Turbine 300", NOT a "PowerGlide". No GTO ever came with a PowerGlide.

WARNING: Most modern shops are NOT equipped to work on the older stuff. You WILL need a shop that specializes in old ones.

Jim

[thatguy101]

well it was driven up till bout the early 80's but it only has 84 thousand miles after that it was parked for years, only driven bout once or twice a yr. but it is the 389, 4bbl, auto, and even when it was driven it started this problem but i good tune up wouldn't hurt but the carb has been cleaned so i don't think that it would cause a problem, the car is all original never painted but it does need some attention other than that thanks for the help

[MrPbody]

Carb has been "cleaned"? Does that mean it has been removed from the car, disassembled, and all new gaskets installed? When was a new fuel filter installed? Those AFBs are fairly easy for an experienced tech, but a youngster with mass EFI experience would be lost.

When was the last time the points were replaced? If none of the ignition system has been replaced since the early '80s, you need to "shotgun" the system, replacing ALL the normal items, regardless of how many miles it has. Plugs, points, condensor, cap, rotor and wires....

You are aware, that engine has a static compression ratio advertised at 10.75:1, with a true SCR of about 10.25:1. That means today's gas won't support it. If timing has been retarded to make it stop "pinging", it will make it sluggish. Old gas in the tank and system will, as well.

After the points and carb are checked, and some 100 octane "race" gas poured in, if the problem persists, I would take it to a transmission shop and have the trans pressure-tested. You can pull the stick and "smell" the fluid. If it has any burned smell to it, the trans is cashed. If the color of the fluid is darker than normal, same thing.

Jim

[thatguy101]

thanks for the help, one more thing it doesn't do is go into passing gear

[MagicRat]

Originally Posted by thatguy101

thanks for the help, one more thing it doesn't do is go into passing gear

Do you know the transmission model?

I think it should be a THM 400, which, as I recall, uses an electric kickdown circuit with a switch attached to the gas pedal. If this switch is not adjusted or has no power, the trans will run perfectly, except will not kick down.

[MrPbody]

MR,

It's a Super Turbine 300. That's the "BOP" 2-speed, often confused as a PowerGlide. No relationship to PG. '67 was first year GTO got TH400.

But... You're right about the kick-down switch. ST-300 uses one, too.


Thatguy,

Try placing the shifter in "L" and driving. Upshift manually. Does it feel like a good shift? Try down-shifting manually by revving the engine a bit and pulling the lever back to "L". Did it go? Or does it feel like it did when you tried it "automatically"? If so, trans is shot... If it DOES down-shift okay manually, look for the wiring and switch MagicRat speaks of.

Jim

[thatguy101]

thanks for the help how much would a kickdown switch cost?