Drivetrain Tranny Shaking

[walkerwma18]

I have a 90 mustang gt that im reabuilding having a big problem though the tranny/engine shaking really rough on a hard launch. ivestripped down the engine and built itback up the engine runs great however if I launch really hard I get a ton of vibration at around 3000rpms that make the whole car shake if I slowly work my way up to top rpms though I get very little to almost no shake as far as I can tell weve fixed everything on the engine and we checked the motormounts took them out they appear to be perfectly intact, tranny mount looks good and all the bolts for engine and tranny have been tightened down. not sure what im missing but I cant figure out whats making it shake so hard. any Advice i can get would be great

 

[Grabbin' Asphalt]

Is this off stock rubber or slicks?? Stock rubber can shake it like a mofo on the track, slip grab, slip, grab, slip, grab. Did it to me at the track back in the day.

 

[GoldenEagle91]

I'm not really versed at all on this matter but could it be U-joints?

 

[Gearbanger 101]

Bad U-Joint is my first guess.

If it were an automatic and happening on the up shift into second I'd say you're feeling "tranny shudder" and could stand a fluid change and the addition of an external transmission cooler if you haven't already got one.

 

[84Ttop]

I have a 90 mustang gt that im reabuilding having a big problem though the tranny/engine shaking really rough on a hard launch. ivestripped down the engine and built itback up the engine runs great however if I launch really hard I get a ton of vibration at around 3000rpms that make the whole car shake if I slowly work my way up to top rpms though I get very little to almost no shake as far as I can tell weve fixed everything on the engine and we checked the motormounts took them out they appear to be perfectly intact, tranny mount looks good and all the bolts for engine and tranny have been tightened down. not sure what im missing but I cant figure out whats making it shake so hard. any Advice i can get would be great

First, auto or manual? We need a little more info on your setup

 

[oldskolbus]

Your only getting the shaking at a certain rpm? something is out of balance. Are you missing any weights on your driveshaft? U-joints good? Tires still in balance?

 

[walkerwma18]

Driveshaft is good tires are ok and u joints are good noticed that if i rev high at stand still i get some shake as well almost feels like motor mounts are bad but i allready checked those

 

[madspeed]

Balancer coming apart? Lookat it while running, does it wobble?

 

[smkshw]

stock tranny mount?....i just did my tko and i got the adjustable cross member,felt tranny wobbling on the test drive....didnt realize i had to weld it...lol....all good now...