I originally posted this in the Transmission forum but haven't received a response, so I'll try here.

While towing for the first time this weekend on my new '01 I noticed a shudder/vibration severe enough to vibrate the steering wheel as well as most of the interior. My setup included a Polaris TrailBlazer ATV in the bed of the truck, and a Triton 8x10' trailer with a Sportsman 500 and XPress 300 ATV's on it. I'd guestimate the total weight of the trailer and all 3 ATV's to be about 2,500lbs.

This shudder/vibration seemed to start around 45mph and would pretty much go away when slowing down or coasting. It didn't seem to matter what gear the trans was in either.

Could this be the infamous "Trans Shudder" that I just did a search on and read about?
Or could it be a driveline issue? If it's a driveline issue what could it be? My towing setup is no different than my old Y2K F-150 and the problem didn't occur there.

Any explanations?

Thanks!



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My New Baby: 2001 F-150 XLT Sport 4x4. 5.4L, S/C, S/S, Bright Red, Dark Graphite Int., 3.55, Class III Tow/Heavy Duty Cooling, 4 wheel disc ABS, Overhead Console, Factory In-Dash CD, Remote Keyless Entry.

Mods: Ziebart Rust Protection, Ford Bug Deflector

Future Mods: Running Boards, Superchip, Air Force 1, Cabin Air Filtration, Ventvisors, Spray-in Bedliner, and Retrax.

2000 Polaris Sportsman 500, Camo Green, 4x4, 499cc 4-stroke, independent suspension, shaft drive, 4 wheel disc brakes, etc.

 

Mine does it periodically too with the camper loaded. I can't tell if it's caused by trans, driveshaft,rearend or road, but I'm leaning towards the winds we had while driving. I think all these combined to set up a resonance.

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Badd Andy

2001 Toreador
F-150 Supercab XLT
7700lb, 5.4L, 4R100
Tow Packg, 3.73
Homemade FIPK
DRL Foglite mod
Headlites Relayed
A/C cutout switch
RS 9000's all around
Bug & Wind deflectors
Dupli-color bed
Lund Premier Tonneau
Short rubber antena
98 ANGLER 8.6 Camper
95 Windstar w/replaced head gasket
97 Susuki Bandit 1200
87 Yamaha XT-350

 

How much did the rear bumper drop with the load? If more than a few inches, your driveline angularity may be on the edge of acceptable.

Try going between OD and Direct -- to see if the vibration is engine speed related and not driveshaft speed related.

Does the shake change depending on drive or coast (power vs no power)? If "no", it suggests driveline -- if "yes" give serious attention to anything that is long and has a natural frequency like that of your vibration. Your exhaust system is then suspect -- as it can go into the shakes under the additional load of the engine. A simple check for exhaust vibration is to wedgre a 2x4 between the pipe and the frame -- or to bungie-cord it, etc..

How'd it go at the dealer today?

Jim

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Y2K™ Jim - N8JG@Hotmail.com

Toreador Red, Keyless XLT SC SB 5.4L E4x4 4wDisc/ABS, 3.73LS, Skid, HD 7700# Towing, LT-245's on Chrome, Tube-Steps, Captain's, 6CD, Tonneau, named: "Nick"

 

Jim, I have to agree with you except for one thing. If the vibration isn't present while coasting but is while the driveline is under torque, the most likely cause is pinion angularity. My new SC has this problem and is currently in the shop to have it looked at. I suspect the spring seats could be welded on wrong. My vibes are in any gear and are torque dependant.

Rob

 

Rob:

How do you explain the difference in vibration between torque and coast?

Do you think the axle is shifting under torque and not under coast?

By torque -- do you mean simply that amount to keep the vehicle at speed -- or WOT?

Are you able to tell the difference between when holding at speed and at coast (with torque convertor unlocked)?

Do you think the axle is winding (and changing the pinion U-joint angle) while maintaining speed -- and/but unwinding (changing the pinion U-joint angle) under coast?

Why wouldn't torque and coast cause the same vibration (at the same speed -- and with axle not wrapping)?

Jim

 

First of all, what I meant by torque is when the driveline is under load such as pulling a hill or accelerating from a stop. I do know for a fact that pinion angles change while under load, although not much. If the joint working angle at the diff. is near maximum allowable for the length of the shaft, and the cancellation angle of the driveline is more than 1 deg., you're likely to have a problem. An unlaiden chassis is less likely to have driveline vibration than a laiden chassis since frame angle changes under weight. If a driveline vibrates while under load and while coasting, it's more than likely due to an imbalance or phasing problem. Since the original post mentioned towing and payload in the bed of the truck, this leads me to believe its a pinion angle problem.

I crawled under my '01 SC and didn't see anything unusual other than a heavy damper bolted to the exhaust pipe ahead of the muffler. I can see where exhaust pulses can produce a vibration that is felt under engine load and not coast, especially if the vibration is independant of vehicle speed, but, if the entire system is properly isolated from the frame, there shouldn't be a problem unless it's due to noise resonance. I do question Ford's exhaust mount at the rear of the trany. It doesn't look as though it would provide enough isolation from the frame.

Driveshaft vibration is usually vehicle speed related since the shaft is turning at a specific speed at a given road speed in a given gear. The cause is dependant on whether it's a first or second order vibration.

I intend to use an Electronic Vibration Analyzer on my truck this weekend to pinpoint the cause. If nothing else, it'll tell me the frequency of the vibration so I'll know if it's engine or driveline related.

 

I know it's a late reply but I had this on my 92 whenever I towed the boat or loaded up the bed with weight. I am convinced it's a driveline angle issue. I recently added 2" lift blocks to the rear and now when the bed is loaded there is no vibration. The guy at the lift shop said the drive angles will cause this.