front wheel drive questions

[Sambor]

I have a M931A2. Couple of questions concerning the front wheel drive system. I have read the ops manual and looked over the TM. When I put the transfer case in low range, I do not get a front drive light indication, or any other lights for that matter. It takes a bit of jockeying around to get it into low as well. If it is in high, I can selective and the engaged light comes on. I can't tell the difference in feel whether it ever really goes into front drive. I read a few of the posts, especially about taking the big washer off the linkage so the driver has to select front drive in either transfer case range. Still need a relatively easy way to tell whether the front is engaged or not. The tires are not scuffing at all-- they look perfect, so I believe it is disengaged normally.

And, I want to thank neverenufhp for the Cummins tips-- All I did was turn up the fuel under the cap plug 5 turns. WHAT A DIFFERENCE! Even for a 5 ton, it ain't quite the slug it was. It makes it a lot easier to drive when it now gets out of its own way. Now if I can get the trans to shift just a mite quicker without standing on the pedal all the time.

John R Dunn
Weatherford Texas

 

[Shrapnel]

In the thread about removing the washer off the linkage for low range auto-front-axle-engage it talks about jacking up one of the front tires and rotating it by hand. If the front driveshaft turns when you turn the wheel, then it is locked in. If the wheel turns but the driveshaft doesn't, then it's not engaged. This is also a way to see if your air lines are installed backwards and if your truck is stuck in AWD all the time.

I'm not sure what the safest way to do this test is. I assume it's best to do it with the truck completely shut down, parking brake engaged and rear wheels chocked, on a level surface. You only need the tire an inch of the ground or so, and you only need one tire off the ground since their shouldn't be any locker or limited slip in the front axle. Once you get the tire off the ground you could try all combinations and see the differences.

 

[M35A2-AZ]

I do not think the light comes on when you put it in low range.
They sometimes can be hard to get into low.
Are you sure the airlock on the transfer case is unlocking when you push the button on the shiftier.

 

[Julian]

Get on level ground and with good air pressure, put the parking brake on which locks the rear axle brakes, jack up one front tire. If you can spin the front tire, the front drive shaft also spins thus being dis-engaged from the rear drive shaft. If front drive shaft and tire do not spin, they are in front wheel drive and the two drive shafts are connected by the transfer case. If the system is operating correctly, in high range, you can flip the lock switch in and out and see the difference.

 

[wreckerman893]

Still need a relatively easy way to tell whether the front is engaged or not.

You will know the front wheels are engaged because the steering wheel will fight you everytime you try to turn.

 

[Sambor]

Big thanks to all for the info. I will try all this weekend. Wreckerman, I wondered if it would do that-- my 4WD pickup does exactly that especially at full lock either way.

John

 

[Shrapnel]

I just tested my m932 to see if the front axle is engaged. I used the video camera on my phone and put it on the front drivers side leaf spring looking directly at the front yoke of the driveshaft. I hit "record" then jumped in the truck and idled forward then parked and shut off phone cam.

 

[Shrapnel]

My truck was in high range without the front switch activated and the front axle was spinning.

So, I guess this means I have a transfer case that is stuck in AWD mode. Now I need to figure out what air lines do what so I can fix it.

 

[Ddmk18]

Just so you know. Since there are no lockout hubs on the front axles the front drivetrain will turn all the time, that is normal.

 

[Greywolf54]

Chain it to a large tree and see if either front tire spins.

 

[Shrapnel]

I thought it wouldn't turn if the front axle was not engaged. Otherwise, what's the purpose of the automatic front axle engagement in low range? What is that switch, or the in-cab switch actually engaging?

 

[Ddmk18]

It engages the transfer case to lock the front and rear driveshaft together. When it's not engaged the front driveshaft will still turn but it won't be engaged inside the transfer case. I hope that makes sense to you. I know it says front axle engagement but it's going to always turn because it doesn't actually engage anything in the front differential. It engages the transfer case to lock the front driveshaft internally and provide power to the front wheels.

 

[Shrapnel]

That does make sense, I just had it in my head that an air line went to the front axle somewhere. I can't feel a difference in steering in AWD vs normal so it looks like I will be jacking up the front end to find out.

Thanks for clarifying.

 

[Ddmk18]

No problem. You will know it's in AWD when turning, my m931a2 really bucks around and tears up the dirt when making a sharp turn.

 

[Shrapnel]

I finally got around to checking my AWD today. I followed the procedure outlined earlier in this thread (started truck, built full air pressure, made sure parking brake was set [then chocked the wheels just to be on the safe side], jacked up one front tire).

My front driveshaft spun when in normal high range and then when I locked in the front axle using the switch the drive shaft locked and wouldn't turn anymore (but I was still able to spin the tire because it is an open differential).

I'm so stoked my front axle engagement is working properly. I finally recieved the title from GL and got it registered today so now I can cruise without worrying about hurting my transfer case. I was so excited I drove it to work!