first drive in the wrecker

[drjconley]

I took the wrecker out on friday to get diesel. I couldnt put it in fifth gear because the engine would lug down and then i would have to go back in fourth gear. i live at sea level with no hills. When i got across town by the gas station i was noticing a pulling from the front, it would happen then go away. I filled it up, and then on the way home in fourth gear I took a left turn, I felt/heard a pop/snap. After that the truck was able to accelerate much faster and i was in fifth going 50 mph, instead of 40 mph in fourth. I filled all the fluids prior to going and everything looked ok after i got home, no leaking fluids, no cracks in housings. Any good ideas on what happened.

Thanks for the help,
Jim

 

[BKubu]

I wonder if your sprag gave out.

 

[drjconley]

would the sprag be the weak link in the front drive system? i was also wondering could it be a drive shaft. i am going to check the front drive system. i was planning on lifting the front, putting it in first and then turning off the truck. if the front can spin, then i would assume there is something not working on the front drive. should the sprag be engaged when driving at 40 mph. any suggestions on where to go next to fix or diagnose the problem.
jim

 

[BKubu]

The sprag can get bound up if you roll backward in a forward gear or forward in reverse. I am sure one our engineer types will chime in with a more technical description of this process. I've never actually torn into a t-case to examine how it works.

 

[drjconley]

would it be possible that the sprag is sticking? if that is the case, couldnt i flush the tranny with diesel or any other suggested fluid. i would think that would be the easiest, fastest, and cheapest first attempt at fixing the problem.
jim

 

[MannUSMC]

It dose sound lie a sprag lock-up, to test to see if it is still loaded and to see if it still works , jack up one front wheel if the tire spins foward one its own the sprag is loaded and may be stuck. Next rotate the tire at least two turns forward the try to turnit to the rear , i should not turn to the rear it the sprag is still working. Don

 

[madsam]

Is there a TM on the sprag. I think mine in not engaging now.

 

[BKubu]

Be careful that your face is not near the wheel when you jack the front end up. Someone on here described a situation where the sprag was under tension and forced the front wheel to spin. Unfortunately for him, his face was against the tire when it did spin...leaving raspberries on the side of his face. It did not sound pleasant.

 

[randyscycle]

If you haven't been into the brakes it is possible that a wheel cylinder or obstructed brake hose or line could have kept a front brake partially applied then finally released after a drive. I've seen that happen a few times on vehicles that have been parked a long time.

 

[timntrucks]

with the slight pull it could have been brake related

 

[drjconley]

the truck has been sitting for years before i bought it. would it be advisable to drive the truck, and if it is doing fine, leave it alone? or, should i start looking at brakes and transfer cases?
jim

 

[emr]

Bleed the brakes, see how/if it works before air is up, brakes on those babys are known to be sticky at times, i personnaly do not know cause, just that more than one wrecker i have seen has had this problem and it was brake related, just some info from me...

 

[tm america]

it will pull if the sprag is locked on dry pavement the sprag should hold one way and freewheel the other if it is holding both ways you rolled the elements and it is junk .ussually when a sprag wears out it will roll to the point it locks both ways . then the next step is for it to break loose and not hold anymore

 

[drjconley]

thanks for all the help, i will keep you posted on how this works out. i wont get to it for about two weeks, i am takeing the kids skiing.
jim

 

[madsam]

This is just a side note, but does anyone know of something you could replace the sprag with to just lock the front in all the time? Then the next thing would be locking hubs. That would help with fuel mileage.. a little.

 

[jwaller]

This is just a side note, but does anyone know of something you could replace the sprag with to just lock the front in all the time? Then the next thing would be locking hubs. That would help with fuel mileage.. a little.

no can do. you have to have the sprag working in this transfer case if you want fwd.

you could, if you had deep enough pockets, replace the stock one with something else but I'm willing to bet you will pay more for the case than you did your truck.

 

[drjconley]

thank you all for the advice. i wouldnt have bought the truck if i didnt have a resource like this. i lifted the front end off of the floor and tested the sprag. it worked as described. i then thought it would be good to change the oil in the transfer case. the color was good, but there was a fair amount of fileings on the magnet. there were no large pieces, and i have been driving it a fair amount and everything works good. i personally think i didnt shift the truck in first after using reverse and the sprag was still in reverse. rookie move. i think i didnt do too much damage, everything appears to work fine. i have noticed that when i shift into reverse i get a definate air sound and a clunk as the sprag is ingaged. i get a similar sound going into reverse, but it is definately not as loud. is that normal, or should they sound identical.
thanks again
jim

 

[BEASTMASTER]

the first time i drove up a hill and let the truck roll backwards still in second gear,the noise was unbelievable. looked under the truck expecting to see all kind of parts, but was lucky, didn't see anything, and everything still worked right. i never did it again though.

 

[M543A2]

We had problems of no power with my son's M139 5 ton bridge truck. We found two problems. The first was the front wheel bearings were bad, allowing the brake drums to rub the shoes. The second was that several wheels had the brake shoe pivoting anchors stuck with rust, which kept the shoes from being returned from drum contact by the return springs. We corrected all of these problems and found new power in road gear.
On these trucks the sprag is engaged by an air shift valve on the trans tower and an air cylinder on the front of the transfer case. With air pressure up, engine off so you can hear, when moving the shift lever from neutral to reverse you should hear a clunk sound as the air cylinder shifts the sprag. If you do not hear it, there is a problem in the shift system, either in the trans tower valve or the cylinder on the transfer. I had to take the cylinder off the transfer on one of my trucks and clean it out and re-lube it so it would again shift smoothly. I also had to rebuild the tower valve on one truck by replacing the rubber seal faces on the plungers in it, a home made fix that saved the high cost of buying a new valve.
Regards Marti