Bad Shake at Take Off
 

I am new here and hoping that someone can help me out on this one. Not long ago I started having a sever shake in my 1994 F150 with the 4.9l and a 5 speed manual. Well it only shook when I would start from a dead stop on level ground or going up hill, down hill I would let it roll a little then let the clutch out and it was fine. There is no shaking at any other time. It shook so bad that it broke the tranny so I just replaced it while I had the tranny out I replaced the clutch disk, slave cylinder and hydro line, new tranny mount and new U-joints in the rear driveshaft, havent hooked up the front yet. It got all back together and it started doing the same thing again, so I just replaced the motor mounts, they where busted too. That didnt stop it either. Can someone point me in the right direction??

Thanks for any help on this one.

It could be a missfire in the engine, usually a miss under load is caused by plug wires or other ign components.

You may simply be getting too much axle wrap at launch which puts the rear driveshaft U-joint at an angle which will translate into a shudder or shake. Weak or broken leaf springs will cause this so maybe have somebody repeatedly put the drivetrain under load while you watch the rear end to see what it is doing.

Thanks for the in put guys, I am doing a tune up today or soon, so I will see how that works, but I think if it was a bad plug or wire that I would feel it when pulling hills and it does just fine a the bigger hill by my house.

The axle and leafspring makes sense too, I replaced the rear spring mount on the passenger side but havent got the drivers side done yet, maybe that is where the shake is coming from.

The only thing I can thing of that will cause a shake like that is oil on the clutch disk. You say you replaced the disk. Did you replace the pressure plate and resurface the flywheel?

Since you replaced the slave cylinder can we assume that it was leaking and that was a source of the oil. If that wasn't the source then maybe your rear main seal is leaking.

When isntalling a clutch, the disk, pressure plate and flywheel must be kept clean and free of oil. Even greasy finger prints will cause a problem.

Hope this helps.

This sounds more like what your symptoms are pointing to, what did the flywheel look like? Hot spots?

I was loosing fluid in the clutch so when I replaced the tranny I was going to do the slave cylinder, but found out it was the hydro line instead, still changed both, the preasure plate and clutch disk looked new, I had to replace the disk because after I pulled it out my son thoght it would be fun to hit it with a hammer, lol. If I have to pull it back apart and replace the flywheel I will do that, maybe next weekend.

I don't know if you have a 2 piece rear driveshaft, but if you do take a close look at the center bearing and its mount, the rubber in the mount gets old and does not support the bearing as it should and can cause some weird shaking at take off and low speeds..

no I dont, it is a one piece, my truck is an extended cab stepside