Bucking or jerking in reverse

[Dieselnerd]

I also have this post in Towing and Hauling but got no response.



When backing my fifth wheel up a slight incline slowly, it starts to buck and jerk. It also does it with my pickup camper in the bed but not nearly as much. I'm pretty sure it's rear spring "wrap" that is causing it. No sign of the problem unloaded.



It did not do this last year with the same trailer.



I only use the fifth wheel to travel South for the winter and I can only think of 2 things I changed since I towed it last year.



1. I installed larger tires, went from 245's to 265's. These are about 1/2 inch taller.



2. I had the transmission modified and now have a much tighter torque converter.



See my signature for other data on the truck.



Any ideas or suggestions? I know this was a problem on some of the first generation trucks with a standard transmission.

 

[M Barnett]

Can't tell you what is causing this for sure, but probably just the dynamics of changing the tire size and the trans mods. If i were you, I would just instal one of the four wheel low range kits so you could back up those grades with the low range. Ever try backing in 4x4 to see what happens?

Michael

 

[Dieselnerd]

M Barnett:

I do back it in 4 wheel low if I'm on dirt, it's pretty smooth then. I rarely get to do that though. Good idea about the 2 wheel low, I just have to block the vacuum from the front axle. I know others have done that.



You are probably right about the dynamics. Bigger tires act as a longer lever to twist the axle and the new TC doesn't slip as much as the stock one did. I can feel what it's doing as it happens. Trying to ease the throttle as much as possible helps some but when it jerks it probably makes my foot press harder and that doesn't help either.

 

[stick]

2 wheel low!!

I purchased the solenoid from www.eaglecontrols.com it is a Numatics L01SA459B. This is a very small 12v solenoid that is used with a lot of the exhaust brakes.

To install, find the vacuum line header along the top of the fire wall just above the fuel filter. You will find a vacuum line going down to the transfer case. All you have to do is place the solenoid in this line, which when activated will block the vacuum from going to another solenoid that is activated when you pull the transfer case shifter in.

So when you have it installed, you turn the solenoid on, and then pull the shifter in, and walla!!

It works very well when backing a heavy load, or when you want to creep over rough terrain, and don't need 4x4.

I hope this is at least clear as mud! It's really pretty simple.



Stick