Hi, I originally posted about this in the SCrew Tranny Thunk thread, but after some experimentation I now realize my symptoms are completely different. My truck is an F-150 SuperCrew with the 5.4 and the limited slip 3.55, it has less than 100 miles on it (got it Tuesday night), and it has the following symptoms.

If I roll forward very slowly (1-3mph), the truck jerks back and forth (front to back, not side to side) as I roll, and makes a thumping noise (rythmic like something is hitting or engaging and disengaging repeatedly). If I'm coasting at low speeds (8-10mph or less) it sometimes jerks back and forth too. This does not happen under significant throttle at any speed. When I stop, sometimes after I let off the brake, it doesn't roll forward, and I have to give it a little gas to get it to go, at which point it makes a little jerk and then goes.

Any idea what might cause this? Any and all help or comments much appreciated, somewhat distressed about tranny problem with a brand new vehicle which I otherwise love to death...

-- Jim

 

That sounds like what I would call "Delayed engage @", which can be caused by several things wrong inside the box. Take it back to the dealer and they should get you a fix (most likely replace the tranny) under warranty.

And without any sarcasm at all, I'm personally sorry for the problem, if you have one. If it's a 4R100, it got past my department (test and repair) when it shouldn't have and contrary to the steroetype some have of UAW workers, I and everyone I work with really care about quality and it bothers me when we screw up. I'm not some papershuffler in Detroit who writes press releases about quality, I'm one of the guys turning the wrenches and if I make a bad part I find it embarassing, I drive a truck with a tranny I built in it, and I want every one I work on to be the one that goes into the next truck I or someone in my family buys. Sounds corny as hell, but that's waht I think and what everyone I work with thinks. We're proud of what we build.

Thanks,

G

 

Thanks for that message, Factory_Tech! I really enjoyed it. Without any sarcasm on my part, too, it's truly great to hear from people like you out there building our favorite trucks! THANKS!

------------------
2000 F150 Harley-Davidson: Superchip, K&N FIPK
Hard Tonneau, Hidden Hitch, 2-Meter Rig (KG0UK)
'99 FLHRCI, '95 XLH

 

Thanks very much for the info, and I, no doubt along with many others here, appreciate your pride of workmanship!

BTW, on further driving this morning, I can add to my description. When it makes the clunk/thump/jerk when I take off (not at all consistent), it can sometimes continue clunking/jerking up to 5mph as long as I' m not hard on the gas. Also, when I stop, it sometimes makes the clunk & jerk, and if it doesn't take off again when I let off the brake, when I give it just a little gas, it starts to roll first then gives the clunk (or the first clunk in the series if more than one) after a few feet.

Still sound like delayed engagement? Thanks very, very much... this will be very useful when I talk to the dealer...

-- Jim



[This message has been edited by JimWright (edited 02-08-2001).]

 

Are you sure it is coming out of your tranny? When I first had my new 99, The rear shoes were sticking a little. Got shoes replaced with new profile,(they had a groove machined down the middle length wise. This solved my problem. Does it constantly happpen or just when the truck is cold - for the first couple of miles?

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99 F150 Super Cab Long Box XLT 4X4

 

Actually, it seems _not_ to happen as much or at all when the truck is really cold. I originally thought it could be the brakes too.

Last night I was reading my manual, and it seemed to say that the adaptive shift mechanism will be trying to adapt to my driving style for the first couple hundred miles. Now I wonder whether it might just be confused for lack of data?

-- J

 

Yep, this morning I couldn't reproduce it at all on a short drive, then this afternoon, I could only get it to happen after I'd been driving for over 1/2 an hour. So, it may only happen after I've been driving a while, and it kind of _feels_ like the brakes are sticking and then catching/releasing, especially when I'm already rolling at 5mph under light throttle. Would this make sense, or is it more likely the transmission?

-- J

 

JimWright-

When I purchased my Y2k 5.4L 4X4, I had the exact same lurching problem under 5 mph. Took it to the dealer, and they said it had a bad slip yoke. Said, the splines were bad on the yoke and that it was hanging up when it should be sliding. Anyway, new slip yoke in and some fresh grease (another cure for the clunk) and the problem went away. Hope this helps. . .

-Rob

 

Well, I'm now up to almost 300 miles on the truck, and it's doing this noticeably less. Factory Tech (or anyone else), what might this indicate? If it goes away, should I forget about it? Something breaking in, or something breaking?

If I can't replicate the problem (which I'm now able to do less often, and less severely, but it still happens sometimes), I'm sure the dealer will tell me to go home. Ideas? TNX...

-- Jim

[This message has been edited by JimWright (edited 02-15-2001).]