Hey guys, I just bought an '86 GT with a 3.4 PR swap and a 4T60 tranny. The swap was done 8 or 9 years ago by "Fiero Bob". The car runs and drives great but when taking off from a stop, anything over 1/4 throttle makes the whole car shutter and kind of jump around and not really go anywhere. While this violent shuttering is happening the engine RPMs increase as if almost free-revving but the car doesn't move forward much.

Today I replaced the automatic transmission filter and about 6 quarts (out of 7) of the fluid.

What it feels like is a loose mount making it all jump around, but the fact that the RPM's climb makes me think something internal to the transmission is bad.

Any ideas? Anything I can check before bringing it to a shop to have them look at it?

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Top Line Group Automotive
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www.TLG-Auto.com
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I know this is a no-brainer, but are you sure the fluid level in the transmission is correct?

Anyway, the first thing to do would be to determine if it's the engine or transmission causing the symptoms. If the engine is sputtering, it should do it in Park / Neutral as well as in gear.

You can check to see if the mounts are loose by holding the brakes (so the car doesn't move), and cycling the shifter from Reverse to Neutral, then to Drive, and back again. Do it slowly and methodically, instead of just throwing the shifter into Drive or whatever. When the transmission goes into gear, it should take up the slack in the drivetrain smoothly. If you hear / feel a clunk, then you may have a bad mount.

Bad mounts shouldn't cause the symptoms you described, though. Actually, based on your description, I'd tend to think the transmission is slipping, and needs a rebuild.

Thanks for the input. Because of the strange way it acts I did a transmission fluid change with a new filter, so we're positive there is enough fluid and that the ATF is good.

I don't think it's a mount, but I'm going to get under there again and check it out. I'm guessing it's something inside.

Could a bad torque converter cause issues like this?

Talked to a mechanic briefly today about the issue and he suggested bad clutches inside the transmission. I'm thinking that getting a good one and swapping it out would probably be less expensive than having this one rebuilt...

You see this one in St. Paul?

http://minneapolis.craigsli.../pts/3999346055.html

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1986 Fiero GT Fastback 3.4Lpr with 4T60
1979 Naked Honda Goldwing

quote Originally posted by Grantman: You see this one in St. Paul? http://minneapolis.craigsli.../pts/3999346055.html

No I did not... thank you!