13 E-450 6.8L Torqshift driveline vibration?

Matt Saunoras · March 13, 2017

I've got an E-450 bus here the customer insists it's got a vibration between 55-60 in 6th gear but it goes away if you neutral it out. Now I did verify it on the highway and on the rack but I can't imagine what it is.

It feels like it's right at the extension housing on the rear of the transmission. Someone very recently replaced the frontmost driveshaft u-joint. I removed the driveshaft and ran the vehicle back up to speed and the vibration while more faint, is still there. The whole shaft looks okay, no weights missing, dents, out of phase or anything like that.

I checked previous hotline contacts for the symptom and suprisingly 2 popped up. Both seemed like the same concern, neither report was too helpful, and both seemed to be resolved by replacing the entire unit. I don't want to go that far I'd like to fix what it actually is.

Before I go ripping this tranny out has anyone heard of or experienced anything like this?

the_twig_187 · March 14, 2017

any vibrations I have ever seen on Econolines have all been drive shaft related. either the upfitters mounted the driveshaft crooked or it had bearing/joint failures or just balance issues

Bruce Amacker · March 14, 2017

I've had many over the years that seemed like a bad u-joint but could not prove it out, pulling the assy and having it balanced fixed it. On rare occasion it was an angularity problem, if there's and easy way (unlikely) to change pinion angle or carrier brg height you might try that. I was on an E450 airport bus the other day that I thought was going to blow the front joint, under load it felt like it was ready to come through the floor....... :grin:

Good Luck!

Edit: " I removed the driveshaft and ran the vehicle back up to speed and the vibration while more faint, is still there."

IIRC the yoke centers the output shaft in the rear housing, running it without a yoke may allow the output shaft to run off center and shake. To replicate this you would probably want to put a bare yoke in the tail and run it.......

cbriggs · March 15, 2017

Yes, to add to that, a worn tailshaft bushing can allow the yoke and output shaft to off-center and vibrate.

Matt Saunoras · March 15, 2017

This tranny has a fixed flange and not a slip yoke style extension housing. I can hear a growl from the rear in that area. I'm not really sure what the deal is but it is powertrain warranty.

Matt Saunoras · March 15, 2017

The front output shaft bushing is totally wiped out in the forward clutch cylinder. I had quite a bit of bushing material in the pan and filter. No idea if this is cause or effect.

I know for sure someone changed the front most driveshaft u-joint. Did it fail and hurt the trans or did they change it trying to fix this problem?

I've got some more investigating to do.

Matt Saunoras · March 21, 2017

Well I may have over repaired this one. Along with the output shaft, extension housing, forward clutch cylinder and forward clutch hub I also replaced the coast clutch cylinder for good measure. Don't tell Ford, the coast cylinder wasn't exactly cracked yet :haha2:

The good news is all seems to be well with this bus for now. I drove it over 25 miles tonight, 10 of which were on the highway to check the vibration. Nothing so far, all shifts are good.