Axle broken? M998 front wheels not turning in shallow snow

[Duster06]

I got my M998 stuck in two inches of snow. I shifted into H/L, and tried to get out of it. My two rear wheels were spinning, but my front two wheels were not spinning at all. I tried adding a little brake pressure to help but nothing worked. I ended up towing it out of the snow with my BMW

I sent the truck to a mechanic out of state and he told me that the front passenger side CV axle was broken and we replaced it. He assures me that the 4x4 is working now.

I am suspicious though, because the front driver's side wheel was not spinning either. Since I had to ship my truck out of state to get it fixed, I want to make sure that it is good to go before I take it back. What does everyone think? Would a broken CV axle on the passenger side have caused all of these issues or is there another problem? The mechanic also said that the transfer case seems good and shifts like other HMMWV's he's seen. I am likely going to pick it up and drive it 4,000 miles to Alaska next, and I'd hate to get it stuck in snow during the winter and be so far away from help.


-Duster

 

[BKubu]

Bring chains.

 

[TOBASH]

Carry a couple of hundred pounds of bagged sand in the back for emergencies.

And BKubu is right... CARRY CHAINS!

 

[cucvmule]

A 4 inch nylon strap, and some rigging, shackles.

 

[Duster06]

My intent is less about how to drive in snow and get a truck out, and more about the mechanical issue at steak here. An M998 is a 4x4 and my front two wheels arnt turning.

 

[DREDnot]

Did you get to see the broken shaft?
Im trying to think why if you tried using the Brake/Throttle Modulation technique that the drivers side tire wouldn't turn while in High Lock?
Unless the drive flange broke at the splines, or you weren't in High Lock when attempting BTM

And like the other were saying...get a set of chains.

 

[doghead]

How long have you had this vehicle?

Have you serviced /inspected all of it?

 

[Duster06]

Did you get to see the broken shaft?
Im trying to think why if you tried using the Brake/Throttle Modulation technique that the drivers side tire wouldn't turn while in High Lock?
Unless the drive flange broke at the splines, or you weren't in High Lock when attempting BTM

And like the other were saying...get a set of chains.

I did not get to see it. I do remember crease leaking out of the rubber joint cover though while working on it.

 

[diesel dave]

Seems everyone is dancing around your question. With a broken half shaft the power would follow the path of least resistance,ie,the the broken half shaft. No power to the opposite side. But by feathering the brake,you might have been able to engage the differential to send part of the power to the opposite side. I’ve never been able to get the diff to do this myself,so in my opinion,this process is sketchy at best.
From what you have stated, you should be good to go with a new half shaft. But with a 4000 mile trip in your future,there’s a lot of pm you should do before leaving.

 

[Curtisje]

Deleted.

 

[Milcommoguy]

BTM does work.

" My experience" and something to get out of one's head.... they're not a tank. It's real easy to get in DEEP with that marcho green machine thing.

It's not an action by just mashing the brake pedal and go. Sure that's the idea... but there's a lot feedback in the "seat of your pants" with watching, feeling, listening to getting the pig moving.

Good brakes all around and a somewhat harder application. A bit of wasted energy is lost in braking to get all the wheels going in the right direction.

If stuck.. "word sounds like stuck ed here" with the look of how did that happen, needing a rig equal or bigger.

Note too, they don't play well in the snow, so be extra careful. Be prepared.

Practice makes for a better recovery, CAMO

 

[Retiredwarhorses]

if you had a broken HS before you got stuck, your truck would have to had been in HL already or you would never have made it out of your driveway to get stuck.
if you broke a shaft, going into HL would allow you to operate the truck...so, none of this makes sense.

 

[Curtisje]

BTM does work.

" My experience" and something to get out of one's head.... they're not a tank. It's real easy to get in DEEP with that marcho green machine thing.

It's not an action by just mashing the brake pedal and go. Sure that's the idea... but there's a lot feedback in the "seat of your pants" with watching, feeling, listening to getting the pig moving.

Good brakes all around and a somewhat harder application. A bit of wasted energy is lost in braking to get all the wheels going in the right direction.

If stuck.. "word sounds like stuck ed here" with the look of how did that happen, needing a rig equal or bigger.

Note too, they don't play well in the snow, so be extra careful. Be prepared.

Practice makes for a better recovery, CAMO

I don't think it will work with a broken passenger side CV.

 

[papakb]

Curtisje, The HMMWV has inboard brakes so even with a broken half shaft BTM works. It is a technique that needs to be mastered and if you've never done it trying to learn it with a broken truck is certainly going to be more difficult. Put the TC in neutral with the front end jacked up and turn the drive shafy\t by hand and see what moves (or doesn't).

 

[Curtisje]

Curtisje, The HMMWV has inboard brakes so even with a broken half shaft BTM works. It is a technique that needs to be mastered and if you've never done it trying to learn it with a broken truck is certainly going to be more difficult. Put the TC in neutral with the front end jacked up and turn the drive shafy\t by hand and see what moves (or doesn't).

Ok. That makes sense to me now. Thanks for the info.

 

[Duster06]

Seems everyone is dancing around your question. With a broken half shaft the power would follow the path of least resistance,ie,the the broken half shaft. No power to the opposite side. But by feathering the brake,you might have been able to engage the differential to send part of the power to the opposite side. I’ve never been able to get the diff to do this myself,so in my opinion,this process is sketchy at best.
From what you have stated, you should be good to go with a new half shaft. But with a 4000 mile trip in your future,there’s a lot of pm you should do before leaving.

so if I understand you correct, you agree that the front left wheel didn’t spin because all the power was being sent to the front right wheel because it had the least resistance? So if encountered again all 4 wheels will likely operate as advertised?

 

[Coug]

BTM Technique

so if I understand you correct, you agree that the front left wheel didn’t spin because all the power was being sent to the front right wheel because it had the least resistance? So if encountered again all 4 wheels will likely operate as advertised?

Read the above article for some information about how the drive system on these actually works.

Short answer though, power will always take the path of least resistance. if one side has less traction than the other, and starts spinning, the differential will allow all the power to go through that side, and because of how things work, that tire will spin twice as fast as if both were turning. It's even worse I believe if you don't have it in lock and all the power from all 4 wheels is going through one.

Biggest caution with these rigs, because of the inboard brakes and sheer weight of the tires DO NOT BRAKE HARD WHEN A TIRE IS SPINNING FREELY!!! That is how axles get broken. Instead, take your foot off the go pedal and let everything spin to a stop, or GENTLY brake to a stop.
Then at this point, having it in HL will send equal power front and back. For side to side, you use the brake throttle modulation. Applying the brakes partway will cause the gears in the differential to lock up, and it will act as a solid axle for as long as you are applying enough brake pressure. (I've found applying brakes with left foot, then using the throttle to overpower the brakes works wonderfully, trying to feather the brakes and keep the throttle steady can be a little harder, but I grew up on a clutch.)

 

[Duster06]

BTM Technique

Read the above article for some information about how the drive system on these actually works.

Short answer though, power will always take the path of least resistance. if one side has less traction than the other, and starts spinning, the differential will allow all the power to go through that side, and because of how things work, that tire will spin twice as fast as if both were turning. It's even worse I believe if you don't have it in lock and all the power from all 4 wheels is going through one.

Biggest caution with these rigs, because of the inboard brakes and sheer weight of the tires DO NOT BRAKE HARD WHEN A TIRE IS SPINNING FREELY!!! That is how axles get broken. Instead, take your foot off the go pedal and let everything spin to a stop, or GENTLY brake to a stop.
Then at this point, having it in HL will send equal power front and back. For side to side, you use the brake throttle modulation. Applying the brakes partway will cause the gears in the differential to lock up, and it will act as a solid axle for as long as you are applying enough brake pressure. (I've found applying brakes with left foot, then using the throttle to overpower the brakes works wonderfully, trying to feather the brakes and keep the throttle steady can be a little harder, but I grew up on a clutch.)

thanks for that article! That’s the first one I’ve seen where it teaches you exactly how to do this technique. It sounds like, since my back wheels were spinning, H/L must have been working, and I bet my front right CV axel was spinning but I was doing the BTM technique all wrong. That would explain in my mind why I was stuck. I don’t think I was putting in nearly enough brake because it all seemed unnatural and I didn’t want to over stress the engine.

 

[Coug]

thanks for that article! That’s the first one I’ve seen where it teaches you exactly how to do this technique. It sounds like, since my back wheels were spinning, H/L must have been working, and I bet my front right CV axel was spinning but I was doing the BTM technique all wrong. That would explain in my mind why I was stuck. I don’t think I was putting in nearly enough brake because it all seemed unnatural and I didn’t want to over stress the engine.

It's an automatic transmission, so it's designed to allow some slippage until it's locked up at cruising speeds. The only thing to worry about the engine is overheating it if you're doing it too long too hard, but a couple minutes in the snow is well within design specs of everything.

 

[Chief B]

When my half shaft broke I'll be honest, I did not try BTM as putting it into HL made it so that I could drive no problem, but I was not trying to drive in snow or anything at that point, just trying to get home. It would however not go anywhere in H, I had to put it in HL.
You mentioned that you "tried adding a little brake pressure to help but nothing worked." From my experience with BTM, it takes a lot more than a little pressure. I recommend that you practice this even just in the snow in your driveway or something just to learn it as it can help you greatly... Come to think of it, I wish I had thought about it last weekend when I was stuck, I may have been able to get myself out...