OK, a new problem with my baby. I very rarely use 4WD, and when I do it's always in the 4 Hi range. Last night on my way home I was on some snow covered / icy roads and turned it on at about 35MPH. The truck immediately slowed down like there was a lot of drag on the front end and there is a noticable "whine" that changes with speed. Anything above 20 MPH and you can feel the truck "swaying" from side to side. I turned it back off and everything seemed normal again.

When I got home I engaged it again and drove slowly. When turning, you can hear and feel the front wheels "jumping", like the inboard wheel is turning at the same speed as the outboard one. Doesn't seem to matter which way I turned, and I couldn't feel one side more than another.

It's an 03 4.7 SLT with 160k on it, no previous drivetrain work done to the best of my knowledge. (I've owned it since 32k miles). Last week I did upper and lower ball ball joints, upper bushings, and shocks. I did have the front driveshafts out for this work, and replaced the CV joint boot because I tore it during ball joint removal. Both shafts appeared to be in great shape and installed again with no problems at all. I don't think there's any way I could have damaged anything as they just "snapped" back in place without much pressure.

I have pretty much no experience working on 4WD, so any suggestions on where to start would be greatly appreciated. Also, would I be hurting anything driving in 2WD?

Thanks for any suggestions.
Bob

 

Could be that you jumped into 4 low range instead of 4 hi.

It is normal to turn in 4X4 on dry asphalt and have the front end hop because the front drive train is locked to the back drive train. The rear moves in smaller revolutions then the front when turning and that is what causes the front end to hop.


You should have no issues driving in 2 hi unless the transfer case is on the way out. Have you done the maintenance on it as you are supposed to do?

 

No, this is definately happening in 4Hi. The only way to go into 4 Lo is to stop the truck and (I believe) shift into neutral first, otherwise the 4Lo light will just blink and not engage.

I understand a little bit of wheel hop, but this was extreme. A noticable "jumping" from side to side when driving. Also, I never noticed that much whine from the front end while in 4Hi before.

Fluids have been serviced normally, although the last one was not done by me. I had it done at a local shop along with the tranny filter. They're normally pretty good with service, hopefully they didn't screw up. I'll get under it this weekend to check things out more closely.

Bob

 

You have to understand that your T-case is fully electronic. What I am trying to say here is if the motor accidentally went to far it could have popped into 4 low without a fail safe.

If you are sure that it did not, then you will need to raise the front end, disconnect the drive line at the front yoke, open the cover and check fluid, and inch pound torque the pinion to ensure pre-load and that everything looks good and feels good. If everything looks good and feels better, then button it back up and drain the T-case.

On the T-case watch for metal flake and look for any wearing as you did the front diff. You might be having an issue in the T-case but without a good overhaul it could be either?

 

Gotcha. I understand what you are saying about the selector motor driving too far and going into 4 Lo, I didn't consider that. I just checked it in the driveway and can hear the motor engaging when I go to 4 HI. It also makes a sound when I go to 4 LO. I drove the truck in both modes and it sounds the same? As I recall, it used to make very little noise in 4 HI )you pretty much didn't know that 4WD was even engaged) and 4 LO was loud.

I'll dive into it tomorrow and update the thread. Right now I've got 10 inches of wet fresh snow to contend with.

Bob

 

Yea, it's snowing like a beotch over here too right now too!

 

Well, it's the old "good news - bad news" thing. Dug into it deeply over the past couple of nights and think that I have it nailed down to the motor that engages 4HI / 4LO is not moving accurately. From what I can see it's a servo-type encoder motor and it's moving too far on shifting to 4HI putting the case into 4 LO instead. At least that's what I'm going with unless someone tells me differently?

Good news is that it's ~$175 and available, so I'll change it out as soon as I can get one. Doesn't appear that I'll be hurting anything driving in 2WD only until then.

Now the bad news, found my minor little tranny leak. The side of the pan has a small crack in it and fluid is dripping out. Looks to me like it was hit with something at one point as the paint is scraped up pretty good on it also. Picked up a new pan from the dealer last night and will swap that out as well, along with the filters.

Has anyone ever modified a pan to incluse a drain bolt in it? Would make those fluid changes much cleaner. It looks like I'd be able to weld in a scab patch to the back of the pan somewhere and drill / tap it to accept an oil plug bolt. Is it worth it?

Thanks for the suggestions,

Bob

 

IMHO, nope. When it's time for a fluid change you really want to change the filters as well, which means pulling the pan anyway.

As for your leak, depending on how long it's going to be until you can put the new pan on, I've had success with slapping a little JB Weld over the crack as a band-aid measure to get me by until I could do it right. (I'm talking a week or two here, don't run it like that for 6 months or anything....)

 

Yeah, that was my thoughts as well. I just hate the mess it makes when you let the pan sit by the back bolts to empty. I end up losing a bunch of it to the floor.

I'll be doing the pan on Friday night / Saturday morning so patching it is not really a big deal. Unfortunately I have to drive it today & tomorrow so I guess I'll be leaving some spots in the parking lots.

Bob

 

Yes, the trans pan can be drilled and modified with a oil plug as there is a kit for it. You will want to have the nut welded on the inside of the pan to keep it from turning and seal better. Just google (B&M transmission plug) and many will come up like http://www.bmracing.com/PRODUCTS/Tra...Drain-Plug-Kit

There is 2 filters on that trans, a flat one and a screw on. Replace the fluid with ATF+4 only! I like Valvoline Fully Synthetic ATF+4. There are no adjustments on that trans you have.

You should be fine driving it in 2wd. There is one other thing though, there is a range selector right by the motor and if that is bad it tells the motor where the position is, if it is giving false information then that would explain why the motor is turning as far as it is.