Stuck in mud or snow

[all thumbs]

I recently was told by a mechanic not to pull a stuck vehicle out by using reverse gear on 4wd. Says its harder on the front drive. Best to turn it around and attach the chain so to pull in a forward gear. I've done it many times both ways with no problem. Think there is any truth to this?

 

[Autotech1]

Re: Stuck in mud or snow

Front drive axles are most often weaker than the rear axle. Also due to weight transfer, in reverse the front axle will get the lions share of the load. So yes it is possible. If your axles are that weak tho you need to stay out of the mud.

What do you drive, and does it have stock axles in it? do you know what size axles they are?

 

[Bondo]

Re: Stuck in mud or snow

Actually,.......It has Nothing to do with the loading of the axles.........

And,... It's very True that you Should do Hard Pulling in Forward gear,+ Not Reverse......

The 3rd Member, or Pumpkins, or Differentials,....Are Designed to transmit the Maximum power in Forward.....
When you Load a Ring,+ Pinion in Forward,.. The Pinion is screwed Into the Ring Gear....
When you load the gear set in Reverse,... The Forces are screwing the pinion Out of the ring gear....
The housings are Not designed to handle the Outward load,+ I've seen the Pinion actually Blown right Out of the Housing.........

If you're going to Pull in Reverse,.... Be Careful......
Pulling in Forward,..... Go for It.......

 

[Bob_VT]

Re: Stuck in mud or snow

Having far too much recovery time in the mud and snow I have a few suggestions..... Snow is fairly easy since it is a traction problem and seldom creates a vacuum under the vehicle.

As far as mud goes.... I like to use a snatch block every time I can. It helps with the physics...... I prefer to be pulling forward only in mud. I have seen pinions unscrew and it is not pretty.

We have gone as far to use an air compressor to pump air under a piece of stuck equipment to relieve the suction.

 

[all thumbs]

Re: Stuck in mud or snow

Use to drive 6 whelers over 26,000lbs. all diesel with limited slip. When they got stuck it was time to call the hook. We would try ourselves when it was snow or just surface grease. Used snatch blocks that have worked but also seen a few break apart. Working for a small operation now with 3/4 ton,1ton, and 6 wheel dump. Get stuck in fields alot. I will print out all your input for the boss to see. Thanks alotd... Bob, I wouldn't want to be on the working end of that air pump:$ wouldn't mind being an observer bond-o, good explanation, i"ll never use my personal truck in reverse!

 

[Autotech1]

Re: Stuck in mud or snow

Some older chevies used rear wheel gearsets in the front, so that in forward motion the pinion was running on the coast side of the ring gear. these gearsets would actually be stronger in reverse.

I say frontends are weaker for three reasons.
1 Front-end ring gears are always a smaller diameter and have less strength.

2 Front ends incorporate u-joints, cv joints or birfield joints to allow stearing, rear-ends do not and they do tend to break.

3 Front ends have ball-joints also to allow stearing, rear end do not, these also tend to seperate when abused.

The rear end is always intended to do the gruntwork. any big load in reverse can and will eventually destroy a front end, and its not always just from ring-gear deflection.

Chevrolet used the same Dana 444 and corpoate 10 bolt rear -wheel gearsets in their front-ends right up to 85 when they switched to IFS.

Ford and Dodge used reverse-rotation gears since the 70s. Ofetn times the stub-shafts running through the spindles will be the first thing to break, theyll shear right off before the u-joint even breaks.

All this is more likey to happen in reverse as the majority of the load is placed on the front tires.

 

[lakelivin]

Re: Stuck in mud or snow

edit: double post

 

[lakelivin]

Re: Stuck in mud or snow

the practical knowledge on this site is amazing....

Bondo, this seems like a good tip to add to the "Mechanical Tricks" post in this forum.

 

[Kenneth Brown]

Re: Stuck in mud or snow

Posted by Auto tech- Front-end ring gears are always a smaller diameter and have less strength.



Incorrect info. See this in your post- Chevrolet used the same Dana 444 and corpoate 10 bolt rear -wheel gearsets in their front-ends right up to 85 when they switched to IFS.

 

[Autotech1]

Re: Stuck in mud or snow

Chevys running D44 and 10 bolt reaer ends didnt use D44 in the rear. They did use some 10 bolt reaers tho. 3/4 ton chevys ran D44 and 10 bolt up front with 10 1/4" ring gears in the rear, DAna 44 and 10 bolt are only aroud 8 1/2.

3/4 ton chevys ran the Eaton 70, then the Dana 60, Then the Corporate 14 bolt in the rear, All of which were bigger than the D44 and 10 bolt.

So the only exceptions would be a half ton truck with 10 bolt front and rear, or a one ton with Dana 60 front and rear.

Generally the front ring gear will be smaller than the rear tho.


for the ford guys the Dana 44 front gears are smaller that the rear 9", and smaller than the 8.8" rear as well.

Ford also did the Double Dana 60s for the one tons.

I dont know that chevy used Dana 44 in the rear of any of there 4x4s as it is not a suitable full-size 4x4 rear end.

 

[Kenneth Brown]

Re: Stuck in mud or snow

Good enuff for me, cleared it up a little better.

 

[50alive]

Re: Stuck in mud or snow

Let me try to add a little something here
The main reason that you should do any hard pulling in forward only is this.
First you have to keep in mind that 4 wheel drive is not a true 4 wheel drive, the front axle and spindles are designed to slip under normal condutions if they didn't you couldn'd drive on them. The truck would want to track in straight line and turning would be tough at low speed and near impossable at high speed. On a hard road they would lock up.
In a turn the outside wheel must run faster then the inside wheel to allow you to turn. if you are going forward and the torque is forward everything will work because the slower wheel can fall behind or slip. But if you try to pull in reverse the torque is backwords and tends to unwind the wheels. This will also happen if you are using the drive line ( engine transmission and axels) for braking down a long hill . 20 years ago they had instruction in the operatpr manuals describing this, at that time they used lock out hubs that you had to ingage when you wanted to use 4 wheel drive and you disingaged then when on hard roads. They don't use then anymore and the drive lines are weaker now because of it. very few vehicles made today will put the full power of the engine on all 4 wheels. Lockers are used on the rear axels but on the front the best you can get is limited slip. even with these the traction is still to load going forward. in the days when you still had the locking hubs if you put a lot of torque on the front wheel in reverse you could disingage the hub and that is still true today.

 

[Deimus]

Re: Stuck in mud or snow

Wrong 50-alive. But just on one thing. I have an ARB front air locker in my jeep and it will lock it so all four wheels can blow smoke. but your right. when I'm "full locked" I can't steer. just thought i'd put my two cents:devil:

 

[Autotech1]

Re: Stuck in mud or snow

50, Whatr u are describing is an all wheel drive vehicle, such as a subaru or mini ute (ford escape). and that is done in the transfercase via a viscous clutch.

REAL 4x4s DO bind in a turn when four wheel drive is engaged, thats why there is a two wheel drive high on the transfer case shifter. Ive owned plenty of 4x4s one i built mysef. nobody makes spindles and hubs that slip.

Manufacturers even tell you not to operate on paved surfaces in forur wheel drive because you can brake a u-joint or break gear teeth just driving in a strait line. This is because no two tires are exactly the same diameter, they all wear slightly different and will cause i bind over so many miles.

as far as backing in reverse (unwinding the hubs...

After unlocking manual hubs, manufacturers instructed you to drive a few feet in reverse to insure that your MAUAL hubs were infact disingaged. this was to release any pressure that could be keeping the dogs from releasing.

During the 80s auto hubs were used, but they worked just as well in reverse. they used a dual acting sprafg clutch that locked as soon as torque was applied to the axle shaft.

Ive rebuilt plenty of four-wheel drive frontends and believe me, ther is no slipping.

 

[puddle jumper]

Re: Stuck in mud or snow

My two cents.
if pulling something heavy with a chain or rope pull in forward gear for two reasons
1- it is safer if the tow rope or chain brakes
2-all trucks are made to have the stress of the load applyed in forward gear.Automatic tranys do not hold up well in reverse under load.As bondo pointed out the difs are not made for a great amount of stress in reverse also.
One last note please use 4low when pulling as discribed
and you truck will love you for it.
just my two cents and 20 years of fixing peoples trucks