Got a 99 f150 bought new, has 115,000 on her now,had some minor problems but she always ran tight except foe one issue.SHUDDER.
Had it from 45,000 miles but it never botherd me,until now.
Has anyone ever found a reason why some trucks have that problem.
Someone at work told me to drain all the fluid and replace it with synthic oil,drain the torque converter also.
Has that worked for anyone.
Last time I changed the fluid was at 50,000 miles on a machine that re-circlelated it threw the system.
Appreciate any help.

THANK'S

 

Could be a low grade missfire but you would likely have thrown a CEL code by now. Try the fluid and filter change its really not a big deal I can and do mine every 2 years in the driveway in about 45 minutes or less. I've heard of a board member who added a friction modifier that made the shudder go away and I've also read good things about amsoil tranny fluid. If you havent ever changed the plugs and coils your over due I'd get the coils off E-bay and some motorcraft plugs and do that to. That might be the problem to.

 

What engine ? 4.2L, 4.6L, 5.4L ?

What trans ? 4R70W, 4R100 ?

 

Appreciate the help,I'll try that tranny change with that amsoil
first and see if that helps,if not I am going to drain the torqe converter and transmission both,never tried that yet.Ive changed my plugs and coil last year and my truck like I said runs great.
My truck has a 5.4 jbrew,with a 4R70W transmission.
Thanks for the help.

 

This is a typical problem with the 4R70W. It's the torque converter mechanical lockup slipping. Usually a trans/converter fluid change will stop it. However, if it has been slipping for 70,000 miles, a fluid change probably won't stop it.

I had the problem with my 95 Mark VIII Lincoln's 4R70W at about 50k miles. I changed the trans fluid and converter fluid putting Mercon V in it and fixed it. Sold the car with 113k on it and still worked great.