Help with weird vibration issue

[carlosinseattle]

I just bought a 91 Q45 a few days ago. It drives really well except for one problem. This happens about 50% of the time. When I'm reaching my cruising speed around 35-50mph, the car starts to shudder/vibrate. It feels almost like I'm riding on really rough gravel or something. When I go ahead and press the gas to increase speed, like giving it 50% or more throttle input, the vibration stops and the car feels smooth as glass. I don't know if it's an injector issue, torque converter, torque converter turbine sensor, transmission, or driveline issue. The vibration doesn't seem to from engine, brakes, or steering wheel. The weird thing is that I can be cruising at 50-60mph and put the car in neutral, and I still feel it. Would that factor eliminate the transmission? Can you offer any suggestions?

[elwesso]

Welcome to the best Q45 forum on the planet!!

I think your issue is related ot the driveshaft... Id consider a replacement driveshaft and a new trans mount to be safe..

You might try the trans mount before you spend $400-500 on a driveshaft, trans mount is about $80

[maxnix]

Can you offer any suggestions?

Hoope you read the timing chain guide article.

[pdqwrx]

Welcome and good luck. I have been fighting/living with the exact same vibration and have rebalanced wheels and tires, replaced transmission and both engine mounts, replaced carrier bearing on drive shaft with zero change in vibration. Now it comes and go's depending on who the heck knows what.

I'll be watching to see what you find....

ThanksScott

[carlosinseattle]

Hoope you read the timing chain guide article.

How would a timing chain issue cause this? Or are you saying to read it for general information on maintenance?

Carlos