'00 F350 DRW 4x4 ZF6. Clutch replaced in Dec 2011, Trans rebuilt in Feb 2012, less than 10K miles on new clutch pack and rebuilt trans. I first noticed it doing this last summer while backing my 35' 5'er up a slight grade into a camping spot, it only did it while backing the camper up an incline. If backing the camper on level ground or without the camper it didn't do it at all. Yesterday I was backing the truck up a slight incline and I was completely unloaded and it started bucking like it did while backing the camper up hill. I didn't think much of it last year cause I figured backing a 35' 5'er uphill is putting alot of strain on it but when it did it empty yesterday it concerned me. This bucking is the only issue I've noticed. It shifts fine through all the gears and only does this in reverse when backing up hill. Is this normal or do I have an issue?

 

[quote=LSO1123;13134544]I first noticed it doing this last summer while backing my 35' 5'er up a slight grade into a camping spot, quote]


I am wondering if maybe you glazed your clutch while doing this? Did you smell and clutch after backing the trailer in?

also check for a "wet" clutch...maybe something leaking up in the valley and contaminating the clutch.

4Lo with the front hubs unlocked makes things a lot easier when backing a big trailer up hill.

 

[quote=clem1226;13134916]No smell from the clutch. Up until about a month ago I did have a leak in the valley draining down into the bell housing that is now fixed. However when I first noticed it doing this last year with the camper, the clutch was new and I wouldn't have thought the leak wouldn't have had time to soak the clutch.

 

Is it chattering as you let out the clutch, or is it bucking after you let out the clutch?

If it's with the clutch pedal released then look at the motor mounts. If it's during the engagement of the clutch then it could be a lot of things.

 

No chattering, it's when the clutch pedal is released. I can actually control the bucking somewhat by engaging and disengaging the clutch.

 

Put a floor jack under the pan with a block of wood and start to jack it up. If the engine tilts one way or the other then the motor mount is bad. If it doesn't tilt then you're looking for something else.

 

I'll get on that, thanks!

 

I just went through the same thing only it happened in 1st and reverse. Your flywheel has some hot spots. (From an oil leak or not turning it properly) You will need a clutch replacement. Make sure to turn your flywheel beyond the hot spots or it will happen again. It will get worse. My transmission guy said with truck unloaded it should not break anything but hooked up to a load and your ujoints and motor mounts could get damaged.

 

Well ain't you just full of good news Shane! Lol. There's a 1000 bucks at least by the time I buy the clutch pac and pay somebody to put it in! I'm comfortable with doing a lot of things on this truck myself but yanking that Zf6 ain't one of them!

 

I paid a local transmission shop $300 for labor $85 to turn flywheel and just under $400 for an oreillys clutch. Fyi.

 

Maybe I'm missing something, but I'm reading that the OP is ONLY having this bucking problem with the clutch fully ENGAGED..

OP, if it's jumpy while your taking off and slipping the clutch a bit, then you probably have hot spots. You can drive for quite a while with hot spots and usually taking off at a little higher RPM will smooth it out. For example, hold RPMs around 800-900 RPM while taking off and the clutch will smooth out, but don't slip it too much unless you want to burn up the clutch.

If it's bucking with the clutch pedal fully released, you DON'T have hot spots on the flywheel. Hot spots will only cause problems while your slipping the clutch to take off. Like said earlier in this thread, if it's bucking with the clutch fully engaged, check the motor mounts

 

It only bucks with the clutch pedal fully released. Pressing the clutch pedal any at all will stop the bucking. Thanks for easing my mind, I was really hoping it wasn't a fly wheel/clutch problem.