When I put my truck into 4-hi and am driving down the road it steers itself all over the place. Kinda scary when the roads are slick. It steers great when in 2 wheel drive. The whole front end has been replaced within the last 4 months so I don't foresee anything wrong up there. Except I did not replace the steering stabilizer shock, could it be that when i have drive force on the front wheels if that satbilizer was bad it would want to wander like this? Also when I put it in 4-hi while driving it has a big clunk that was never there before, I can hear and feel it through the floor. Any ideas about this? Thanks for any ideas!

 

Tires all need to be the same, exactly the same size, even if two are worn and the others new you will feel it. If they are not the same then one tire is always slipping and that could be what you are feeling.

 

Ok, thank you. The tires on the back are probably 85% tread and the fronts probably about 20%. Could it still be noticeable with the tires on the front being worn down that much more, i mean from the front to back tires?

 

Probably not, unless they are actually different size tires.
You aren't driving it in 4WD on dry pavement, are you?
If you have movement in your front end, being in 4WD, and the different loads imposed while driving in 4WD, can magnify the loose issues. I would focus on what your clunk is.
Also, if someone has put a locker in the front or rear, that will change your driving characteristics.

 

Thanks guys for the input. They are the same size tires, other than being worn down differently, and no I am not driving on dry pavement in 4wd and there are no lockers on it. I will try and find out what that clunk is and report back as soon as possible. Thanks again, I really appreciate the ideas. Hopefully they all will help me narrow down and find the problem.

 

Even wet pavement will cause problems since the tires are not going to slip very easily. In snow, dirt or mud the front to rear speed difference is absorbed by minor slipping of the tires. You should only use 4wd off road or in snow.

Rick

 

+1 Very hard on drivetrain. Plan on breaking parts driving on pavement in 4x4.

Another thing to consider is that the front tires have more weight on them, so they squat a little. I was a little skeptical of this having an effect on diameter/effective gearing, but 4wheel and off road did a side by side test and proved that lower pressure affects the final ratio by making the rolling diameter smaller.

So why does this matter? Because on high traction surfaces like pavement (even when wet) the fronts cover less ground due to the tires squatting. This will make the rear tires push the fronts and the drivelines will wind up and unload. Especially in corners. Even offroad I have such significant driveline windup in my truck in corners that I finally converted my CAD unit to be manual so I could drive in 2wd low range. On pavement, I'd be afraid of breaking axles.

 

Well here is an update so far: I checked the u-joints and the axle joints and did not find any play in either. Although I think i might just replace the u-joints anyway because when it is in 4x4 I can feel a vibration that seems to be coming from the driverside floorboard. I can also hear a faint ticking when moving and my head out the window, hard to tell though with the engines loudness. I also checked the steering stabilizer and there seems to be even pressure going in and going out. I looked harder for more vaccuum leaks and found none, I did find that right at the vaccuum pump the 90 deg. rubber angle on the end of the vaccuum line was really soft and worn(If I squeezed it it would not return to shape immediatly like fresh rubber should) so I replaced that. I then took it down a very loose dirt road and no more steering wander and no more clunk It seemed to shift into 4-hi very well and it sometimes took a little longer when shifting out of 4-hi, but it never did the clunk even once. Maybe when I was checking the u-joints, one was bad and i didn't notice it and it stuck in a different position. After i replace them I will update more and maybe the vibration will be gone. Thanks again for any and all ideas! When I first noticed the problem I was driving on an icy dirt road covered in about 6 inches of snow. I also rotated the tires yesterday as well.

 

U-joints can also go bad by seizing up, especially on the front. That will cause all kinds of steering problems.

Rick

 

[QUOTEWhen I first noticed the problem I was driving on an icy dirt road covered in about 6 inches of snow. I also rotated the tires yesterday as well.[/QUOTE]

In this particular situation, I have another suggestion for what you may have been hearing. The overload springs slapping the main pack or the auxillary overload springs (only on some trucks) smacking the frame bumpstops.

When driving in thick snow or sand, random spinout and axlewrap can make this happen. Might be nothing wrong at all. U joints are pretty obvious when they go bad-if you didn't find anything obvious, I'd forget about them for a while. If one lets go, in most circumstances it can be driven on for quite a while. IE won't leave you stranded.

One other thing which VEXES me about the diesel trucks is the funky single piece leaf spring bushings. On my truck they let the main eye of the leaf spring contact the frame and make funky noises. I have tried to source a poly kit, but last I checked they are only available for the 2.5" wide gas engine trucks. The diesels get 3" springs. This could make some funky noises, too.

 

Rickf, do you mean the u-joints at the ends of the axle(if that's what those are?) or on the front driveshaft?

totalloser, I do agree with you but the clunk was only there when I would put it into 4x4, it would clunk one or two times just when engaging and it sounded very much like it was coming from the front axle somewhere. As to the leaf spring bushings, I understand your vex because I have the same problem, bad bushings. I jsut spray them down with wd-40 once in a while and where they touch the frame and make noises it quiets it up. I know that's not permanent but it gets me by for now.

Thanks guys!

 

I am talking about the joints at the ends of the front axles.They can seize up and depending on where they are when you turn they can make for a very stiff turn and sometimes no self return. They can also cause hopping in a turn on a front axle without CAD and in 2WD. This usually only happens on those axles when they have locking hubs and 4WD is not used very often.

Rick

 

If the tires are not all the same circumference then one of the four tires must slip. What messes up the handling is it's not the same tire that slips every time so you can't tell what's coming. I feel a difference on my 4X4's. I didn't used to think it was worth the money to run all tires the same but if you go fast on ice or poor slippery conditions you'll see why I changed my tune. For what it's worth my $400 worth.

 

the tire difference will make you steer funny in 4 wheel drive.

I did not think these trucks were shift on the fly.
I thought you had to stop to put them in 4 wheel drive.

am I wrong about that?

I bet your clunk is from shifting on the fly/ slightly spinning in the snow and ice.

I thought the vacuum dissconnect on the axle dissconnects the one side and all the rotation from the other tire or most of it is taken up by the spider gears in the diff.

guess I will go grab my manual and look it up.
I am new to these trucks. all my old ones are lock outs and gear driven transfercases.

EDIT:

just looked it up, they are shift on the fly for 2wd to 4wd hi at below 55 mph.

also, it says you should be rolling slowly 2 to 3 mph with the truck in neutral to shift into low 4 wheel drive.

so I will stick by the thought that you were spinning a bit when you shifted into 4 wheel drive.

 

Another update: I replaced all 3 u-joints on the front shaft today and one was really rusty and had no grease inside of it, the other 2 seemed ok. Put everything back together and thought I'd add a little bit of fluid to the transfer case. I checked it the other day and it seemd to be about a half inch below the fill plug. I started filling it and it ended up taking almost 3 quarts(not good)! I have not seen any leaks since I had the tranny rebuilt and all new gaskets on t-case. I'm thinkin they may not have filled it back up after they had it toff for the transmission rebuild. Test drove the truck and still the same vibration, It is different now that I rotated the tires though. I'm almost about to just drive the darn thing till she quits, I know I have alot of miles on it but it does get old! I am probably gonna get some new tires in the next few weeks and see if that will change anything. Will keep ya'll posted if I do anything else. I am going to replace the u-joints on the back shaft as well since I now have vibration all the time. Rickf, is there any way to really check these joints without pulling the axle shafts? Thanks again!