No drive without CDL engaged (1 Viewer)

[nickolai]

Hi guys

I was away from my truck for a bit today (diving). When I came back, parked on grass, I drove straight forward, then turned slightly. There was a loud bang and no drive.

I straightened up, and went into reverse. Would not reverse.Put it into Netural, then D, no drive.

So, engaged the CDL and had drive. Drove about 10km at 50km/h (windy, sealed road). Truck drove fine. Could manueveur on concrete with no binding or skipping.

So, I’m thinking I’ve blown the front diff? (Hoping so because that’s an easier fix and want to do swivel hub rebuild too).

I popped the caps off at the drive flanges- not stripped

What does everyone think? Can I drive on the road with the Centre diff locked? Should I pull the front driveshaft?

1994 HDJ81 auto full time AWD.

 

[-Spike-]

If you broke anything between the transfer case and either axle it would act that way. My bet is on a birf, but that's just the odds, and the fact that you were turned a bit. The bad news is that the broken parts might jam and really screw something up, or even prevent you from turning at an inopportune moment. If you must drive it, I'd remove the driveshaft and drive flanges, so nothing in the axle moves. Even better, pull the broken birf and axle shaft, if that turns out to be what's broken. You'd have to seal the end of the axle tube as well, to keep the diff oil out of the knuckle. You could drive it indefinitely that way, assuming your improvised axle tube seal holds.

You can probably at least identify which side is broken by lifting a tire and rotating it. Nothing else should move (such as the driveshaft, or pinion flange if you pull the driveshaft) if it's the broken side. Or maybe you'll hear crunching...

On second thought, I'm not sure that would work, although it should at least identify which axle has an issue. Once you do that, you might be able to lift both tires and compare how much effort it takes to move each tire. One of them should be connected to the diff and therefore require more effort to move than the one with broken stuff.

 

[nickolai]

Hi all,

update. With the truck not running, In Park and CDL locked,if I jack one wheel up at a time, both front wheels turn freely. One sounds a little crunchy but not bad.

when I do this the prop shaft does not spin.

It’s late now, but tomorrow I will pop the drive flanges off and report back.

 

[nickolai]

Hi all,

update. With the truck not running, In Park and CDL locked,if I jack one wheel up at a time, both front wheels turn freely. One sounds a little crunchy but not bad.

when I do this the prop shaft does not spin.

It’s late now, but tomorrow I will pop the drive flanges off and report back.

update. Same setup as before. Turning one of the wheels, it spins free (ish) for a portion of the rotation. Then it feels like it’s loading up and there’s a metallic ting noise from the front 3rd member. The pinion flange moves a very small amount. It feels like it’s loading up then it becomes free. Doesn’t take much effort, can do with a couple of fingers.

 

[BILT4ME]

update. Same setup as before. Turning one of the wheels, it spins free (ish) for a portion of the rotation. Then it feels like it’s loading up and there’s a metallic ting noise from the front 3rd member. The pinion flange moves a very small amount. It feels like it’s loading up then it becomes free. Doesn’t take much effort, can do with a couple of fingers.

If you have one wheel off the ground, one wheel on the ground, then turn the wheel off the ground, the driveshaft must turn. If not, your differential is broken.

 

[too tall]

If you have one wheel off the ground, one wheel on the ground, then turn the wheel off the ground, the driveshaft must turn. If not, your differential is broken.

Sorry, that could be a birfield as well .

 

[nickolai]

Thanks, even with the CDL engaged?

 

[BILT4ME]

Sorry, that could be a birfield as well .

No, if neither front wheel turn the front DS the that is differential.

 

[nickolai]

No, if neither front wheel turn the front DS the that is differential.

Ok, so my current state is, engine not running, in park, CDL engaged. Jack up one wheel at a time, Both wheels spin, and neither spin the driveshaft. One has some rumbling, which isnt constant in the rotation, which could be the birfs (if broken) but also leads me to (perhaps incorrectly) suspect the diff due to the ring and pinion ratio etc.

So, my plan of attack to get to the bottom of this (will start tonight after work).

1. Jack up both wheels simultaneously and check for differential action (e.g wheels spin opposite ways). Normal operation in this situation, (park, CDL engaged), should be that the driveshaft doesn't turn?

2. Pull drive flanges and check for stripping. I should also be able to check the Birfields too - unusual movements etc

3. Pull front driveshaft. With both wheels off the ground i should be able to turn the pinnion flange, and both wheels should turn opposite directions? Will check for noise etc too. I will also check through the fill plug for broken teeth on the ring.

4, Remove wheel hubs and spindles to check for broken birfs

Steps 2&3 mean that i can keep the truck mobile - i only have a few hours after work each night this week to trouble shoot.

I will also check that with thr front DS removed and the CDL not engaged that I dont have any horrendous noises from the transfer.


Does this sould like a sensible plan of attack? I would just tear it all down straight away because i was going to do the front axle anyway, but i need to keep it semi mobile for a bit (eg no front DS and drive flanges) as its a semi-dd and it will take a while to get parts anyway.

thanks

 

[-Spike-]

Nothing you've done so far will tell you what part is broken.

What you know, according to what you did in post number 3, is that something in your front axle is broken. That's it. Nothing points at any particular part. Nothing points at the diff in particular, and it's not the weakest link in the assembly, by far. And as far as I know there's nothing you can do to figure out what the problem is without disassembling at least one knuckle. I'd start with the one that "sounds a little crunchy but not bad". How is any crunchy not bad? Let me rephrase that. Crunchy is bad.

My money is still on a birf. Not because of any of the evidence, just because it's the most likely. Well, crunchy does support it a bit.

I'd pull the drive flange off the crunchy side, and try to spin the birf. If you can do that by hand, it's probably not connected to anything, so it's likely either it or the axle shaft is broken, but there's still a chance that something in the diff is broken. If you can move it easily through a short range, same thing. But to actually know what the problem is, you'll have to dig in to it.

 

[-Spike-]

No, if neither front wheel turn the front DS the that is differential.

Normal operation of the diff is that if the driveshaft isn't able to turn (CDL locked, rear tires on the ground) the tires will rotate in opposite directions. If something is broken (anything, anywhere in the axle) then the two wheels are not connected. The diff may be doing exactly what it's supposed to do, but it's not connected to the opposite wheel.

 

[ppc]

Nothing you've done so far will tell you what part is broken.

What you know, according to what you did in post number 3, is that something in your front axle is broken. That's it. Nothing points at any particular part. Nothing points at the diff in particular, and it's not the weakest link in the assembly, by far. And as far as I know there's nothing you can do to figure out what the problem is without disassembling at least one knuckle. I'd start with the one that "sounds a little crunchy but not bad". How is any crunchy not bad? Let me rephrase that. Crunchy is bad.

My money is still on a birf. Not because of any of the evidence, just because it's the most likely. Well, crunchy does support it a bit.

I'd pull the drive flange off the crunchy side, and try to spin the birf. If you can do that by hand, it's probably not connected to anything, so it's likely either it or the axle shaft is broken, but there's still a chance that something in the diff is broken. If you can move it easily through a short range, same thing. But to actually know what the problem is, you'll have to dig in to it.

This is all spot on and the only way to proceed.

 

[nickolai]

This is all spot on and the only way to proceed.

Thanks guys. Understand 100%. I'm just looking for ways to minimize the downtime.

 

[ppc]

As long as you are able to lock the CDL you can pull birfields one at a time and if necessary reassemble the spindles to be able to drive temporarily. If you end up finding carnage in the diff both birfields would have to be removed anyway. You can still drive without the diff just cover all the openings with some plastic and tape.

 

[JakeVII]

When this happened to me [1991 FJ80] (no drive except 4 low or CDL engaged) it wound up being that the drive flange was stripped and had to be replaced. It wound up being a full front end rebuild. It wasn't fun, or cheap, but it was still worthwhile; I wouldn't have redone the full front end otherwise.

It was a bad time when it happened- I was at a stop light, light went green and...no go. Tried all gears and nothing happened. Didn't try CDL or 4 low at the time, which could have limped me to a mechanic.

 

[nickolai]

Hi all.

Really appreciate all the input so far. Houston, we have found the problem.

 

[nickolai]

Hi all!

Just rounding this one out. Over the weekend I redid the whole front axle, bearings, seals, new shafts, new CVs, new spindles etc. I stimulated the Economy via the Terrain Tamer dealer here in Auckland! This has been on my list for a while but I'm glad i did - there were some weird things going on. This is my first front axle job on an 80 but I've done plenty on 40s and 70s.

On one side the wheel bearings had marrred the spindles quite badly, and both the hub seal surfaces were marked. The spindles were mismatched - one had a roller bearing, the other didn't. On one side the knuckle had been sealed with silicone. Wheel bearings and Kingpin bearings were buggered too. The inner axles were buggered too - standard wear where the seal rides. I'll speedi-sleeve these and they can be spares.

I have however found out that i need new brake calipers (siezed pistons), so new ones are on their way from Mr T. I would try rebuilding them but i think they're too far gone. Once i get the new ones in i have them rebuilt as spares.

We're in Level 3 lockdown here for 2 weeks so won't be going very far, so all good waiting for parts!