Hello. I have been trying to track down a problem on my truck for a while. There is something in the drivline binding somewhere that really cuts the power down. I had blamed it on the brakes but as bad as the problem is you'd think they would be smoking hot after a trip but they dont get very hot usually. Neither does the transmission, transfercase or axle.
What ever it is must be "bound up" most of the time because whenever it free's up, the truck feels like it has an extra 100hp and it coasts much better.

Just because nothing seems to get hot surely does'nt mean ther is'nt a problem.

What can I exactly can I test for to be binding in the axle(LSD D70), getrag, np205, brakes???

Any help would be awsome, thanks.

 

You could take out one drive shaft at a time and run it. See if you can isolate the problem a little bit.

I took out the rear drive shaft once and ran my truck as a front wheel drive when I was trying to track down a noise.

JP.

 

Could be slightly different size tires on a locking differential. If it locks up, the tires would be dissipating the heat. Probably no noise or heat in the gears. You probably feel it as a bind or erratic steering.

If it isn't obvious by checking tread wear and/or sidewall info, dropping one drive shaft at a time would help locate it, maybe. If the diff is working properly it would. If it locks up randomly, it could do it without being driven.

 

jogl~ I never thought of that, I might give that a try.


j_martin~ I bought the tires as a set of 6, Im prety sure they are they're the same size and the rears are wearing really well, no uneven wear visible. I'll check that out though. The diff is fairly worn out, it pops if I make a tight turn at very low speeds. You've got me thinking now, I replaced the rear yoke on the diff a couple years ago, if the torq was off could that be the problem??

 

I was able to find a Dana repair manual online and some torque specs for what it should take to rotate the yoke with and without a carrier installed, but you still would have to pull the axle shafts to check if it is overly tight.

Is there any possibility on a fuel related issue? Air leaks in the lines or something along that track? Is the fuel pressure the same when it runs good and bad? Does it smoke the same when running good and bad?

I'm with you on the brakes - they would have melted off by now.

 

Well, it feels just like the brakes are dragging. The fuel pressure seems good, I was at one time thinking it might be a fuel issue but I found out when its "binding", it is even when the clutch pedal is pushed like when coming to a stop. So i'm prety sure its a drive line issue.

My manual says the torq on the yoke nut should be around 250-300ftlb. I'll check that. You say theres a spec for the rotational torq? I'd like to check that too, but the axles have to be out? Would'nt be a problem really.

 

Put it up on jack stands, start at the wheels and work in. If you've got a bearing going you should be able to hear it when rotating the wheels. If you don't find anything there, go to the drive shafts next. On a side note, if you have access to an infrared heat gun it can be very helpful locating binding issues. They produce heat and if you can see it you usually can read the temperature. Draw a diagram of your truck with the locations you want to check, including u-joints and write down your readings. If you can't disengage your front hubs don't forget the steering knuckles at the end of the front axles. You might have to turn the wheels from lock to lock to get a reading there.

 

Good idea on the heat gun. Harbor freight sells them and it should at least be good enough quality to find a hot spot.

 

Ok, that gives me some good info to start with. If you think of anything else, don't hesitate to post it up Thanks

 

I did think of one more thing. If your engine cooling fan is staying engaged that will rob a bunch from you.

 

Is it in 4x4 all the time?

 

Have you check motor and transmission mounts? Looked for broken springs, shackles etc? Do you have manual lock out hubs? I think the heat gun idea is a great one, test everything that spins or moves. Cheap ones aren't accurate at all but it doesn't matter it will still show you a hotter spot.

 

Totallyrad~ The fan seems to work good, I can tell when it kicks on as it "roars" prety good. thanks though Im still prety set on the problem not being directly related to the engine.

j-fox~ No, it goes out of 4x4 but the front axle spins sometimes. I can hear it click occasionaly. The bearings that are in the ends of the axle are in need of changing. But it only spins sometimes at about 25+ mph.

gyman98~ Engine and trans mounts are fairly new and look good. I might check the trans mount bolts though. I had it appart a while back because the plate under the trans snapped and I had to weld it. I do have locking hubs which I replaced a couple years ago, the front axle spins freely when parked also. I too like the heat gun idea. Accuracy probably would'nt matter as much in this case, since I just need to find spots that are hotter than others.

I'll jack it up and check everything ya'll listed. Any more ideas, post them up. I'll probably start looking it over this weekend. Thanks

 

I just noticed you have a club cab, check your carrier bearing and mount too

 

I would think the rubber mount would rip before it ever could drag a cummins down