Lately when I have been coming to a complete stop the tranny is jerking. It feels like there is a trailer behind the truck that is banging into the rear when stopping. Does anybody know what causes this. The truck is a 4x2 with 5.4L. Thanks.

 

Are you sure it's the tranny? Seems like rear brakes grabbing or rear end hop. could cause that symptom. Try putting some load in the box and see if the problem eases.

 

Honestly I don't know what it is. It almost feels like it's shifting hard but instead it does it when you come to a stop. Actually, I noticed it this morning when I was at a stop light and I let off the brakes to move forward. So now it's doing it when coming to a stop or when leaving from a stop.

 

Could your torque converter clutch not be disengaging properly? you might try turning off overdrive as soon as you start it up, before you drive - and then go for a test drive to see if the problem goes away....

Sounds like a transmission problem to me - hanging up when it downshifts.

Allen

 

Maybe tranny, but could also be fractured ring gear in the rear end. Did it start right after some specific event such as having to stop suddenly or towing something very heavy, or heavy exceleration etc etc? Just looking for anything that happened out of the ordinary to cause it may help you figure out what it is.

 

Wouldn't a fractured ring gear cause other problems also, such as noise at highway speeds?

 

True the ring gear usually will cause a noise at highway speeds as well but not always, especially if you only broke off one or two teeth. Just stating that it could be ring gear and besides it is really cheap to pop the dif cover to check. Anyway, while you got the cover off you could also replace the ol trash gear oil that comes in it stock and put in a high quality synthetic.

The main question that really needs to be answered is this.

Did you do anything out of the normal range of driving to cause it? Or did you say, tow a really heavy load then noticed shortly there after? Did you pop it from R to D while still rolling backward? You know anything that would cause a sudden change in direction of travel? Did you let your wife, kids, friend or anyone else drive your truck that could have done something and not told you about it?

Really need more info to get an idea of what is happening without seeing, hearing or experiencing it in person. I would at least check your basic driveline components such as driveshaft, wheels, u-joints, dif, leaf springs, shocks, all mounting points. Best thing I can tell you is look at the little things first that you can inspect then if you can't find the trouble take it to the dealer or a good mechanic and let them ride in it to hear what it sounds like and feel exactly what is going on.

 

Just a guess.

Put some grease inside the slipyoke.

 

No, I haven't really done anything out of the ordinary. Actually I have never towed anything behind the truck. The heaviest thing I put in the truck was 1.5 cubic yards of dirt, but that was about six months ago and this just started recently. The truck is treated like a baby. I think 03FX4 hit the nail on the head. I tried driving without O/D on and the jerk effect seams to have stopped. I even drove on the highway with O/D on I turned the O/D off to force it to downshift before I came to a complete stop and the jerk did not occur. So I think this is O/D related. This is definitely a dealer problem since the truck is still under warranty. Since my knowledge on transmissions is limited to manual trannys only, Could someone explain to me what is going on here so that I may prevent it in the future? The truck has 27,000 miles and I haven't touched the tranny fluid yet. What is the recommended fluid change interval?

 

It may be a dry slip joint on your drive shaft loading up when you stop.

Pete

 

Let's see if I can explain what's going on without getting into boring detail.....

Years ago, people who were concerned about gas mileage wouldn't think about buying a car with an automatic transmission. In order to not kill the engine, there must be some way to disconnect the driveline from the engine when the vehicle stops. With a manual transmission, the clutch performs this function. On an automatic, the torque converter does the job. If you have ever made Kool-Aid, then you already have a good idea how a torque converter works - as you stir, the Kool-Aid starts to rotate in the same direction as the spoon is rotating. If the liquid had some way of getting traction on the outside of the pitcher, eventually the pitcher would start to rotate as well.

In a torque coverter, the outer shell is physically connected (bolted) to the flywheel of and rotates with the crankshaft of your engine. This outer shell has "vanes" on it's inner surface and is full of transmission fluid. As the shell rotates, the fluid rotates with it. At the center of the torque converter is a vaned shaft which is attached to the input shaft of the transmission - so, as the shell rotates, the fluid rotates, the center shaft rotates, input shaft rotates.......Knee bone, shin bone, ankle bone, etc.......

Since only fluid (hydrostatic pressure) connect the transmission to the engine, it becomes possible for the transmission to be stationary while the engine continues to idle. In the past, the downside was that because the fluid coupling always allowed some slippage, the engine always rotated somewhat faster than the input shaft of the transmission. This caused the automatics to always trail the sticks in the gas mileage race, because the clutch in a manual transmission makes a solid connection between the engine and transmission.

The trick that they came up with to solve this problem was to install an electromagnetic clutch inside the torque converter. Sometimes you will hear this referred to as a TCC (Torque Converter Clutch) or generically as a Lock-Up Torque converter. This clutch works much like the one on your air conditioner compressor - an electrically activated clutch pack engineered to form a mechanical connection from the outer shell of the torque converter to the transmission input shaft.

This clutch is programmed to only be engaged under certain conditions - part throttle, over a certain speed - basically cruise conditions. It should disengage when you start braking, to allow some level of "engine braking".

I suspect that this is where your failure is happening - for some reason, it is not recognizing when you start braking. Here's an easy way to test (if your truck has a tachometer). Get on the freeway and drive at a steady speed - 55-60mph (don't use the cruise control) reach over with your left foot and press the brake pedal just enough to make your brake lights come on. Your RPMs should increase slightly when you do this, and then drop again a few seconds after you release the brakes.

If your truck does not behave like I described, I would be willing to bet that the dealer will be able to fix this by a adjusting or replacing a brake pedal switch - I would be surprised to find out that your transmission was actually broken. You are probably coming up on your fluid change interval, but I doubt that your fluid has anything to do with your problem, and I seriously doubt that you have gone past the recommended interval.

Sorry I ran on so long, it turned out to be a bigger subject than I originally figured.

Good luck with however it turns out!

Allen

 

Allen, thanks for the explanation. Very insightful. I will try what you mentioned this evening. It is definitey something with the tranny. I have also put the tranny in neutral while coasting and then coming to a stop with it in neutral and the hitch effect has completely disappeared.

 

Did this problem ever get fixed? What did it end up being?

Allen

 

Sorry, hasn't been fixed yet. I've been up to my ears in work and haven't had a chance to get to the dealer yet. I will post when it gets fixed.

 

Well, 4 months later and I finally got it fixed. Actually I was hoping someone here can help me figure out what they did. The repair sheet says the following:

R&R Drive shaft and lube slip yoke with teflon grease
road tested 3 miles -OK-.

When reading it the first time I thought it was a poor excuse for a fix and that I would have to bring it back in because they didn't fix it. Well I was wrong. It simply doesn't do it anymore. I guess my main question is what does R&R mean? Because I don't think greasing the slip yoke would fix this problem. My first guess would be "removed and replaced" Am I correct? Thanks.