Hello,
I have a 1999 F250 super duty with a mean vibration at 70+ mph. It is a 5.4L manual trans manual 4x4 extended cab short box with around 250k miles on the body and 50k on the motor. It is a one piece drive shaft with the double knuckle at the t- case. it has had a vibration in the drive line since i bought i about a year ago. there is almost zero vibration at 60 mph but at around 70 the vibration starts to get really bad. The vibration is speed related because when i push in the clutch or pull it out of gear the vibration is still there. i seems to vibrate more when winding out in 3rd and 4th gear but that may just be because off the exhaust resonating or something. I have already done u-joints, balanced the drive shaft, put brand new tires on mounted and balanced, replace transfer case output bearing and both front hub assemblies. the vibration feels like it is coming from the trans or transfer case. every thing i tried made very little impact on the vibration. I'm a loss and i don't know what else to try. i know the throw out bearing an pilot bushing are bad and the clutch is well worn so ill be replacing that soon but i don't believe that is causing the vibration. Any Ideas???

Thanks

 

Welcome to FTE, '99 5.4L DUTY .

Where do you feel this vibration? In the set? The steering wheel? The pedals? Maybe in the gear shifter?

Does the frequency of the vibration change with the truck speed or the engine RPM?

Does the amplitude change with frequency or engine RPM?

 

Welcome to FTE!

I agree with you that changing the clutch isn't likely to make any difference if it's speed related. The clutch doesn't care one little bit how fast the truck is moving; it's all about engine speed. How do your tires look? Have you had a tire shop rebalance them?

I went CRAZY trying to fix a vibration in my Excursion, and after 5 trips to the dealer it ended up needing a new driveshaft. Of course you've already done that, but the bulk of their efforts were focused on the tires and pinion angle. Have you had your driveline angles checked?

 

I put brand new tires on it mounted and balanced and did not make a difference. also it is stock ride height.

 

The vibration is really prominent around the floor around the trans hump and in the gear shift. the manual 4x4 handle shakes like crazy. above 70 it vibrates enough to make the dash buzz. in 3rd and 4th gear winding out it feels like it seems to make the vibration worse

 

I just drove it yesterday and i can also feel the vibration in the pedals. I changed the transfer case bearing and balanced the drive shaft and not 50 miles after putting it together the output seal on the transfer case is leaking badly. i went to the ford dealer an order the tail house bearing for t-case and a ford seal. I'm not sure if that will fix my vibration issue but hopefully it will stop the bearing from leaking.

Also im buying a clutch kit for it this weak, is there any thing i should check while i have the trans split from the engine??

Thanks

 

I'm sorry you're not getting more suggestions.

I was rethinking this today, and I'd almost think that you have something wrong internally with your transmission. The transmission output shaft, transfer case, and driveshaft don't care what gear the transmission is in because they are at the same speed regardless of gear. How does it feel in 6th? Does it still noticeably vibrate?

I believe these vibrations could damage bearings and oil seals over time; and I think the leaking output shaft seal is a symptom but not the problem.

 

Its a 5 speed but in 5th it seems slightly less of a vibration than when in forth around high way speeds but very very little and i think it my be just how it resonates with the rpms. it really doesn't care if its in gear neutral or in gear with the clutch pushed the vibration is the same. it does seem to be a little worse on decel. The tabs on the extension housing that hook to the trans mount are broken off, probably from when the previous owner replaced to motor, but i created basically a giant exhaust clap to go around the extension housing and connect it to the trans mount. i feel the it is well mounted and stabilized now and considering doing this cause very little change i assumed it wasn't the source of the issue.

thanks