when coasting car surges front to back feel it in my pants

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87 gta 5.7ltr
edelbrock headers
gutted cat
flowmaster 3in drivers exit
8.8mm wires/accel
accel 300+digital ignition system
msd pro billet distributer
hypertech stage 2 racing chip
slp cold air intake
maf has no screens
52mm bbk throttle body
extruded plenum, runners, intake all matched
high flow fuel pump
afpr @ 50 psi
ALL MODS DONE BY ME FOR ME
waiting on hotchkis rear susp package
and sfc before i run hard at track

 

i have never had a problem like that before. does the car vibrate at high speeds?

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86',88',89' IROC-Z, 350 TPI, 700-R4

94' Formula, LT1, 6spd

 

no i checked u-joints
drove again noticed rpms bouncing from 550 to maybe 800 but i still feel/hear a i guess you would say knocking from underneath

 

Maybe the torque converter locking and unlocking. Tap the brake just hard enough to kick on the brake light(will unlock the converter). When you do that, does the surging quit?


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350 with stealth intake, holley carb, 470 lift cam. 700r4 with .5 boost valve, vette servo, tci lock-up kit, B&M megashifter. Richmond 3.73 gears, powertrax locker, timkin bearings, synthetic lube. Custom 3 inch single into 2 2.5 pipes. 1 1/2 drop springs, 1 5/16 solid front sway bar, 1 inch rear bar, custom subframe connectors, custom LCA relocation brackets. Kobel ground FX, currant red metallic paint. Lots of other stuff...
82camaro

 

hey guys, i have that same damn problem, although i have a 305/5speed, steady rpm, usually below and around 2000 rpm, it rocks front to back and is annoying, i have a vibration around 70mph seems to be more of a vibration when i de-accelarate, my rear end is messed up though

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86 Camaro with 88 305 LB9 using 86 carb setup, edelbrock performer manifold, 305 S/R Torquer Heads, Hedman Headers, Crane Compucam 2032 edelbrock cat-back, gutted cat, slp underdrive pulley, mallory ignition, 305 h.o dual snorkel air cleaner, hypertech thermomaster chip,160 degree thermostat, 5-speed, 3.23 posi

95 Beretta Z26, 3100 V6, 4 Speed auto, stock