this one is really interesting, my 700r-4 makes a slapping sound from 2nd to 3rd only and only when i dont get on it or gas it hard if i drive "normally" it pops really loud i checked the suspension all is fine. so i cant firgure out what the hell it si please help?!!

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1989 firebird formula

Mods: converted from T.B.I. to a carburator 305 to a 350. Flowmater exhaust,hedman shortie hedders,202 heads,350 horse cam,bored.40 over, Edlebrock torker2 intake.

Future mods 400 performer rpm intake (polished) and 600 edlebrock carb, comp roller cam, and way better heads. orpossibly a 383 stroker?

 

check the brace that hooks to your tranny and goes back to the diff.

 

I used to have almost the same problem. It turned out to be the TV linkage travel distance. At WOT it was fine and shifted great but at regular or part throttle it shift hard and make a loud pop because the carb was returning the TV cable to far back. But i found a web site that tells you exactly how to set it up..... http://205.178.174.23/sumner/techinfo/700R4p1.html It's got a lot of good info for your (and mine) trans. Hope this helps.

89 RS Conv 305 700R4
85 HO heads
Performer RPM Int
Holley 600
Hedman Hedders and Y pipe

Drove the first one like i stole it and had to buy another one.

 

checked out the page you supplied and i have to do the test where you let it shift from first to second and then nail it to see if it kicks back down to 1st! i'm keeping my fingers crossed thats the problem! it only has 34,000 miles on it !! i'll email you to keep you informed!

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1989 firebird formula

Mods: converted from T.B.I. to a carburator 305 to a 350. Flowmater exhaust,hedman shortie hedders,202 heads,350 horse cam,bored.40 over, Edlebrock torker2 intake.

Future mods performer rpm air gap intake (polished) and 600 edlebrock carb, comp roller cam, and way better headsa 400 defintely in the works!