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TH400 problem?


Canuck

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The 71 SS454 I purchased last summer is the first car I've owned with a big block and TH400. With all the 350/TH350 cars I've owned over the years, the car wasnts to move when I put it into drive. The 71 SS however will just sit there when in drive unless I give it some gas. This does not seem right. It seems to drive fine otherwise and does not have any significant leaks. Could this just be a torque converter issue or maybe the tranny itself? I'll have to check again to see what the fluid level is at, can't recall if I checked this when I got the car.

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I don't know what mods may have been done to the car. I do know the engine was rebuilt to stock specifications and runs great. Maybe they put in a different type of torque converter? I don't know. I don't have any experience with high stall converters. All my cars have been stock.

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I can't remember how my original TH400 behaved as it has been a while since I had it in my car, but when I had my new TH400 installed with a 3500 stall it would move when put into gear. After that one blew up I had it rebuilt and used the same 3500 stall converter and it behaved completely different, now I have to give it gas to get it to move forward. I am no transmission guru but it has to be how it was built to behave differently...tighter/looser???

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When it is in neutral what are the rpms? When in to drive what are the rpm's

Fluid checks are always good. When going through the gears are you noticing a increase in revs but power remaining the same?

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None of you asked me if my e-brake was on... blush

 

Turns out my e-brake was on a little. Very odd since I rarely use it. The release does not seem to pull it up all the way. The car moves fine now...

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None of you asked me if my e-brake was on... blush

 

Turns out my e-brake was on a little. Very odd since I rarely use it. The release does not seem to pull it up all the way. The car moves fine now...

 

That should help your gas mileage. Sounds like the parking brake cable just needs some adusting.

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Yeah, there was a funny smell after driving it yesterday and the rear rims were HOT after driving on the highway. My dad was the one who said "could the e-brake be on?" Now I'm concerned that the heat may have damaged the bearings or something else in the rear. Hopefully it is OK.

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No, the light was not on. Funny thing was that it popped on after I figured out the problem and was testing the parking brake. So, I know the light works. I have not had a chance to look at the parking brake assembly yet to see what might need adjustment. For now I'll just make sure it comes up all the way after using it.

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Glad to hear it was something simple. I have done the same thing in my Firebird. I drove all of the way to work wondering why the car was so down on power. When I got to work I went to apply the parking brake-but it was already fully applied oops lol. That was years ago and there were no long term ill effects. David

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Yeah, there was a funny smell after driving it yesterday and the rear rims were HOT after driving on the highway. My dad was the one who said "could the e-brake be on?" Now I'm concerned that the heat may have damaged the bearings or something else in the rear. Hopefully it is OK.

 

Are you sure it wasn't that yacht you were towing? laugh

 

Seriously, I superheated my driver's side brake by driving with the park brake on (not sure why both sides didn't suffer) and that is the side where the oil seal was deformed and leaking. Sounds like you may have heated up both sides pretty good.

 

It is easy to see how a super hot brake drum would transfer enough heat to the axle hub and the flexible rubber-like lip of the oil seal which presses on the axle shaft just about an inch inboard of the hub. If the seal was damaged, it may be quite awhile before visible evidence shows up unless you go looking for it. The easiest way I know is to pull the wheel and the brake drum and then feel the backside of the hub to see if there is fresh oil there. If there is, you will eventually have to replace the seal or your brake assembly will become a gummy, oily mess like mine recently did.

 

Hard to imagine it was bad enough to damage the wheel bearing. It would almost have to boil all of the lubricant out of the bearing so it ran dry under load - surely you would have smelled or seen smoke before then. My driver's side got so hot that smoke poured out of the brake drum for several minutes after I finally discovered it. I didn't notice any degradation in motion with a manual transmission. Hope your situation is not too serious.

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The brake light is not going on when I push the parking brake pedal down. It went on briefly yesterday after I released the parking brake and went away when I pushed the brake pedal so I know the bulb works but maybe the switch at the parking brake is not working.

 

As for the rear end, both wheels got pretty hot so I'll pull the drums off and check for signs of leaking fluids.

 

Thanks guys for all your support. smile

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I think a common mistake Aaron. Did the same thing when partially engaged. I noticed resistance and through trial & error identified the culprit. Didn't see the brake warning light on but after further investigation determined it was working properly. I have since just got into the habit of pulling the park brake release to make sure before I take off. blush

 

Doug

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I would worry mostly about the brake shoes cracking due to the over heating but nothing else. More than likely no problems though.

 

Really we assumed you would have already checked that. Maybe the cable needs some grease, may be some rust on it preventing it from fully releasing.

rob

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