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Bucking and clunks when shifting... ZF6

  #1  
Old 05-08-2018, 11:09 PM
beef tits
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Bucking and clunks when shifting... ZF6

Alright so this has been going on for a while. When I am driving like a normal non-dingus, my truck bucks and clunks when I take it out of gear.. like something is binding in the drive-line. This happens usually when I am slowing down while in gear, and pressing the clutch in coming to a stop. When I am hot-******* it (full-on dingus), this doesn't happen. It's only when I am in like 1st/2nd gear in a parking lot.

I know this is a big dumb truck and big dumb trucks are just heavier and clunkier in general... but is this normal?

Also, I just pulled a truck camper and a trailer with another truck on it halfway across the country. CO to OH. 11 MPG at 60-65 MPH. 9 MPG at 70-75. Woof!! I sprung a minor fuel line leak somewhere along the line (small drips at every stop) and am hoping that was a big contributor. Was hoping for 13-14 at least with that load... about 9k lbs total.
 
  #2  
Old 05-09-2018, 08:52 AM
NO_SPRK
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if the engine rpm changes when you take it out of gear i would check the ICP sensor. my zf6 truck can tend to hunt idle and run a little funny when coming off of a running rpm when pushing the clutch in.
 
  #3  
Old 05-09-2018, 09:07 AM
Walleye Hunter
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I haven't driven one of these in a manual but...of the trucks that I have driven with manuals many of them have some odd characteristics in the lower gears. Some of them would act like the clutch was still engaged even though the pedal was pushed to the floor and they would be hard to get out of gear if the RPM's didn't match for the speed of the truck and the gear it was in. Then if and when they did come out the trans would clunk back and forth from the pressure being released. The only solution to that was to hold slight pressure on the stick before hitting the clutch and sliding it out of gear simultaneously while depressing the pedal.
 
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Old 05-09-2018, 10:18 AM
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Originally Posted by NO_SPRK View Post
if the engine rpm changes when you take it out of gear i would check the ICP sensor. my zf6 truck can tend to hunt idle and run a little funny when coming off of a running rpm when pushing the clutch in.
Good call, My ICP sensor is newer but a generic ebay one, characteristics have not changed since swapping it out. It does seem to hunt for idle at times though, I should probably get a Motorcraft unit as well as a new pigtail.

Originally Posted by Walleye Hunter View Post
I haven't driven one of these in a manual but...of the trucks that I have driven with manuals many of them have some odd characteristics in the lower gears. Some of them would act like the clutch was still engaged even though the pedal was pushed to the floor and they would be hard to get out of gear if the RPM's didn't match for the speed of the truck and the gear it was in. Then if and when they did come out the trans would clunk back and forth from the pressure being released. The only solution to that was to hold slight pressure on the stick before hitting the clutch and sliding it out of gear simultaneously while depressing the pedal.

Good to know. My clutch/flywheel/trans rebuild/driveshaft/rear end rebuild all have less than 10k miles on them so if this is how it is... I'll just have to get used to it. I've always owned smaller Toyota trucks and sportscars which were much smoother to shift and drive all around... I guess I'm not sure where to set the bar / what to expect with this Pig.
 
  #5  
Old 05-09-2018, 06:23 PM
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I guess my zf6 is a flawless unicorn. I don't have any of those troubles Walleye. Neither did my 88 chevy 5spd 1500, nor does my 71 F100 4 spd, or even the corvette. Maybe you rode in beaters with poor maintenance?
 
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Old 05-09-2018, 06:29 PM
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Originally Posted by Wesley Green View Post
I guess my zf6 is a flawless unicorn. I don't have any of those troubles Walleye. Neither did my 88 chevy 5spd 1500, nor does my 71 F100 4 spd, or even the corvette. Maybe you rode in beaters with poor maintenance?
Hmmmm....now that I think about it the trucks I'm thinking of were back in the '70's, one was a Dodge and the other a Chebby.
 
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Old 05-09-2018, 06:29 PM
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I just changed my ICP sensor and the little bit of bucking right off of idle from going in reverse has gone away now I think it's mostly the chain driven transfer case and how smooth your shifting
 
  #8  
Old 05-15-2018, 10:24 PM
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Mine does the Same thing you described, the key is to be easy on the clutch petal. The ZF6 is a bit of a clunky transmission in the lower gears. Also the chain in the transfer case has nothing to do with it, all the chain does is send power to the front axle in 4x4, in 2wd the chain isn't engaged it just spins freely.
 
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