Drivetrain Clunk/Jerk/Slack/Pop
#1
Drivetrain Clunk/Jerk/Slack/Pop
99 F150 XLT 4x4 SCab Short Box
5.4 Triton w/ 4R70W & BW4406 TC, 3.55 NON LS Rear
150,000 miles
Problem:
When I let off the gas while going about 60 mph, I get a heavy "thud". It repeats that thud when I lightly get back on the gas pedal. It happens at mostly highway speeds. It's slowly getting worse. I've tried several fixes, but to no avail.
Fixes Tried:
Changed tranny fluid and filter. {NO CHANGE}
Pulled driveshaft, inspected slip yoke (no obvious problems). greased the crap out of it with synthetic grease and reinstalled it. {SLIGHT CHANGE, BUT ONLY TEMPORARY}
Checked U-joints. Installed new Front U-joint. Rebalanced Drive Shaft. Lubed the Slip Yoke with Moly Lithium Grease. {NO CHANGE}
It's shifting good. It's running great. I just feel slack in the drive line somewhere. I cant find it. I need help.
My company mechanic thinks that it may be the "Rear Output Shaft Bushing" in the Tail Housing of the Transfer Case. (I drained and refilled TC Fluid. it was pretty and clean like brand new) This bushing is brass I think, and it goes around the slip yoke inside the TC tail housing.
I think it could possibly be the Transmission Mount. How can I tell if that bad short of removing it?
Thanks guys.
5.4 Triton w/ 4R70W & BW4406 TC, 3.55 NON LS Rear
150,000 miles
Problem:
When I let off the gas while going about 60 mph, I get a heavy "thud". It repeats that thud when I lightly get back on the gas pedal. It happens at mostly highway speeds. It's slowly getting worse. I've tried several fixes, but to no avail.
Fixes Tried:
Changed tranny fluid and filter. {NO CHANGE}
Pulled driveshaft, inspected slip yoke (no obvious problems). greased the crap out of it with synthetic grease and reinstalled it. {SLIGHT CHANGE, BUT ONLY TEMPORARY}
Checked U-joints. Installed new Front U-joint. Rebalanced Drive Shaft. Lubed the Slip Yoke with Moly Lithium Grease. {NO CHANGE}
It's shifting good. It's running great. I just feel slack in the drive line somewhere. I cant find it. I need help.
My company mechanic thinks that it may be the "Rear Output Shaft Bushing" in the Tail Housing of the Transfer Case. (I drained and refilled TC Fluid. it was pretty and clean like brand new) This bushing is brass I think, and it goes around the slip yoke inside the TC tail housing.
I think it could possibly be the Transmission Mount. How can I tell if that bad short of removing it?
Thanks guys.
#2
#3
I thought that the front drive shaft didn't spin unless it's in 4wd. Am I wrong?
I had the drive shaft balanced because my company mech (he's seems fairly competant at working on cranes and rebuilding diesels, but this shook my confidence) pulled it and removed the front U-joint and played around with the slip yoke. While getting the ujoint out, he broke the cast iron damper ring off the slip yoke. Then it started vibrating at about 60mph. WHen I had my wife take it to the only place in frikken Birmingham, AL that balances drive shafts, they said the front U-joint was shot. They replaced it for $15 and balanced the shaft for $40. When I got it back, it still kinda vibrates, but not as bad, and seems to only do it in deceleration between 70 and 60mph. I assumed that they didn't replace the rear U-joint cause it didn't need it. I havent seen any slack in it.
I feel like the clunk is coming from between the transfer case and the rear tires. When I'm in 4wd, the sound is gone. It only happens in 2wd.
Tons of fresh grease in the slip yoke that slides into the transfer case seems to help, but not totally eliminate the noise for about 10 miles.
It's starting to clunk now when I take off from a dead stop. Not every time, but fairly often. When I say dead stop, I mean a red light, where I never take it out of drive.
I had the drive shaft balanced because my company mech (he's seems fairly competant at working on cranes and rebuilding diesels, but this shook my confidence) pulled it and removed the front U-joint and played around with the slip yoke. While getting the ujoint out, he broke the cast iron damper ring off the slip yoke. Then it started vibrating at about 60mph. WHen I had my wife take it to the only place in frikken Birmingham, AL that balances drive shafts, they said the front U-joint was shot. They replaced it for $15 and balanced the shaft for $40. When I got it back, it still kinda vibrates, but not as bad, and seems to only do it in deceleration between 70 and 60mph. I assumed that they didn't replace the rear U-joint cause it didn't need it. I havent seen any slack in it.
I feel like the clunk is coming from between the transfer case and the rear tires. When I'm in 4wd, the sound is gone. It only happens in 2wd.
Tons of fresh grease in the slip yoke that slides into the transfer case seems to help, but not totally eliminate the noise for about 10 miles.
It's starting to clunk now when I take off from a dead stop. Not every time, but fairly often. When I say dead stop, I mean a red light, where I never take it out of drive.
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#7
Well, I believe I found my culprit. I removed the rear diff cover, jacked up the rear end, and started spinning the tires and the drive shaft by hand. I didn't notice the problem till I started turning the ring gear with a pry bar. Every time I torque the ring gear with the pry bar, I see a gap appear between the "Pinion Shaft" and the "Differential Case". It is accompanied by the elusive popping noise I've been hearing. Any change in direction of the spin or the amount of torque applied, I get my Pop sound and the gap appears.
For reference, if you have a haynes manual for 97 - 03 ford pickups, go to chapter 8 -16and look at picture 16.4a and 16.4b.
Does this sound plausible? Is the pinion shaft supposed to be tight?
For reference, if you have a haynes manual for 97 - 03 ford pickups, go to chapter 8 -16and look at picture 16.4a and 16.4b.
Does this sound plausible? Is the pinion shaft supposed to be tight?
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