OK.. When I put the truck in 4 wheel drive it loses it's power.. it will speed up a little and die down.. hardly pull up a hill, but once it's outta 4 wheel drive lots off power. I tried a new PMD and put on a new LP.. same thing. Appreciate any help...thanks

 

What do you mean speed up a little?the engine speeds up or the truck speeds up?????

 

When I put it 4 wheel drive it has no pulling power, you can put the peddle too the floor and it won't rev past past 1500.. it might go down to 1100 or a 1000 and maybe back up to 1500, but once it's out off 4 wheel drive everything is fine.

 

Sounds more like an electrical problem than a mechanical problem too me. Its strange, the exact same thing happened to my friends half ton dodge and we couldn't figure out what happened, lucky for him we were in New Mexico where 4x4 simply isn't need at all.

Might want to check your wires down there, on a 98 I assume that there is some electrical components to the 4x4 system. If it works fine in 2wd then don't mess with any of the fuel system components since they work, its something when you flip it into 4x4 that gets it. Could be a dirty ground not getting good connection, but who knows.

When you put into 4x4 does it smoke more than usual or not, and are there any trouble codes popping up? Any information helps.

Good Luck

 

No codes or smoke, where I live there's lots off hills so I use 4 wheel drive alot..I noticed today it would loose it's power when it was shifting from first to second, (it's a automatic) as soon as it would try to shift into second it would go into limp mode, no power.Then I tried shifting it down into Second gear.. perfect lots off power, that was a nice relieve.. once I put it back in drive the same thing.. but it works great in second gear. Would the AC compressor have anything too do with this, I removed it a couple off weeks ago cause the bearing went, and I put a by pass pulley on there.

 

It shouldn't, but the AC and draw lots of power, I don't think it would unless somehow your 4x4 wiring and AC wiring are connected to each other, but it might be pulling that pulley and cranking on it like the AC is on. Well did this start right after you took the compressor off, basically what did you change right before you noticed this was happening? That's always a good place to start.

 

The only thing I changed was the AC compressor, and I drove the truck for about a week before I had too use 4 wheel drive. When it started doing this first I thought it was the P.M.D.. changed that and the L.P. It could be that Compressor.. like you said the 4x4 and the AC wiring are connected somehow. I'm willing to bet that's the problem.. everything worked fine on the truck till I removed the AC compressor, it was a week later before I noticed it because I didn't use 4 wheel drive.

 

Yeah if it only started doing that after you took the compressor off, that would be a great place to start. I know my AC will draw tons of juice away so I just don't use it, bad idea in New Mexico, just don't need it in Montana.

If it is electrical it could be real simple or loads of fun. Anyway, I just though of a temporary fix that might work. So on the pulley where the compressor was, there should be an electrical connector that should be activated when the AC button is pushed from the cab. Anyways if you just disconnect that it should stop if it that is the problem. But you mentioned a by-pass pulley, if its spins freely then whether the AC is "on/off" shouldn't matter, since all pushing the AC button in the cab does is pulls in the clutch on the compressor making it work, it pulls the pulley whether the AC is on or off.

But start by unplugging the AC connection and see if that fixes it, I have my doubts thinking about it. Worse case scenario is that you are getting excess slip when in 4x4 meaning your actual 4x4 components are failing.

Good Luck

 

Right now there's no AC Compressor on the truck,when I removed it I had too unplug two connectors. It just has a pulley on there now. I wouldn't say the trans is slipping, cause when it would try too shift when the RPM'S would go up and the truck would pick up speed also. I think the only to do is try another Compressor and that's around 600 bucks, that's y I went with the $40 dollar pulley.

 

I wasn't talking about the slip in the transmission, there shouldn't be excessive slip there if it works fine in 2wd. I'm thinking there might be something wrong with the front differential. I think the actual compressor is what draws the power when on so with just a pulley, you shouldn't lose any power even if the truck thinks the AC is on. The only other thing I could think of would be the ECM is at fault.

I just thought of something, your wheels might not be getting power to them. You would only get roughly half of the power to the rear wheels and half to the front in 4wd and if your front wheels aren't gettin any power, you might feel like you only have half the power as you do in 2wd. That's the only other thing besides the ECM that I could think of is causing this. Try jacking all four wheels up and see if you can get the front ones to spin or not.

Sorry I can't be of more help, I've only owned one vehicle (as I am only 18) and its a 2wd so my experience with 4x4s are limited. Good Luck