Bang/Pop/Lurch on Engine Braking

[Groelzj]

Ok, first off, this is my girlfriend's truck. It's a 2004 Ranger with suicide doors.

Her driveway is steep and rocky so every time she goes up or down, she puts the truck in 4-low. It has started to bang and lurch forward a foot or so and then catch itself. To begin with, it only happened downhill, but now she's getting the same thing going uphill and it's happening with much more frequency going downhill. The transfer case is a BW 1354 electric and she's had it in to several mechanics who can't diagnose it. One suggested the Transfer Case, she replaced that with one from a junkyard and it solved the problem...for a month. Now it's back and quickly getting worse.

She now rides the brakes down the hill with the clutch pedal to the floor (about 1/4 mile down steep grade) instead of using engine braking.

One mechanic said it may be the passenger hub, the next guy said there were no vacuum or wires to the hubs, so it doesn't have auto-locking hubs, the truck has live spindles engaged at the transfer case, and the last guy *thinks* it could be the driver's side hub...he said it looks a bit worn, but told her she's not doing any damage to it when this happens.

Where should I start? Do you need any more information or pictures? Any ideas? I'm mechanically inclined, but not familiar with 4x4 systems.

Manual hubs are too inconvenient for the frequency she uses her 4x4 and it worked for a long time before this started happening...but I don't know what the root cause for the slip is.

Thanks in advance!
Jon

 

[pillen140]

if she replaced the transfer case once and it fixed it for a while... thats probably the cause. i wouldnt use 4wd especially 4low on a rocky driveway. only in loose dirt or mud/snow. probably damaging something. only use 4wd if you have too. see if it does the same thing in 2wd. check the whole drive line for visible damage aswell.

 

[Groelzj]

The reason for the 4wd is that her driveway is loose rock. 2wd vehicles don't usually make it up the driveway, their drive wheels just sink into the loose rock until they bottom out and have to be towed by a 4wd. We live in Hawaii and she lives on a 50 year old lava flow, so it's porous lightweight, loose rock.

The real trouble is that there are strips of cement to drive up on the steeper parts, so you're going back and forth from rock to cement, but you really do need 4wd on the rocky parts. If she had another $15k laying around, the real answer would be to pave the whole distance and go up in 2wd, but the steepest parts are a strain on even 4wd vehicles in 1st gear high range, low range makes it super easy to go up and down, but inconvenient to do "properly" because you have to stop to shift from 4low to 4hi/2hi and you *shouldn't* be in 4wd at all on the pavement, even though it's super steep.

 

[pillen140]

is it auto or manual? could be quite a few things. when it happens going up hill, can you hear a tire spin? does the motor rev up? does it slam hard when it picks back up?

 

[Groelzj]

It's manual, I haven't noticed any tire spin and yes, it does slam hard when it picks back up. I don't remember if the engine revs when it happens, definitely not when going downhill and engine braking, it doesn't happen super often going uphill, but it's happening more often than it used to. It's her car, so she drives it a lot more than I do, I'm going from my limited experience and memory here...She won't be able to read this until after work tonight, probably after you guys are all in bed.

Oh, forgot to mention it in the first post, but the transfer case motor was replaced with a new one by one mechanic, and when that didn't fix it, he swapped the old one back in and didn't charge for the work.

Thanks for the help, btw!

 

[pillen140]

i wouldnt think its the transfer case actuator... usually when that goes it will not move from what ever position it is in. is the 4x4 light flashing when it happens?

 

[Groelzj]

No, 4x4 light stays lit the entire time.

 

[Original_Ranger84]

Well she should not use the 4 lo going down, up is fine. Did the U joints get replaced when the Tcase was replaced?

 

[Groelzj]

No, U-joints were not replaced.

4-hi going down still gets the slip, 2-hi going down is doable, but you're relying on the brakes instead of the engine to keep your speed down...ok short-term, but not a great long-term solution.

 

[Groelzj]

She read it and here are the corrections/missing pieces.

Got a chance to skim through. You pretty much got it right. No one quite seems to understand that 2wd or even 2high is not the greatest option on grades of up to 18% with loose rock. I know there are concrete strips for a hundred feet here and there, but I'm not taking my truck in and out of 4wd 5 times in a half mile stretch. The strips in themselves are somewhat uneven and rough. A nice slow crawl, especially when I'm carrying loads, prevents slipping and burning out brakes. In 15 years, I've never had our driveway wear out or present unusual wear and tear on a decent transfer case. And no, it's not just the tires slipping or me driving too fast.

History:

4x4 started making intermittent popping, or slipping sound, going downhill. At first it was only in 4low and only downhill. No real regularity (as far as time or distance travelled) but it definitely seemed to correspond with workload. Worse on steep parts, worse if the rpms got higher. By the time I replaced the transfer case a couple months later, it was every few seconds going downhill, somewhat regular going up, occasional in reverse, and also in 4high. Never happened in 2wd.

Got transfer case from recommended junkyard and replaced. Problems seems gone.

Maybe, maybe 2 months later, the problem started returning. And, just like the first time, it started off very occasional and quickly got steadier.

Rather than throwing money at another transfer case, I took it in for testing to see if the problem was bigger than just the transfer case. First mechanic eliminated the hubs, differential and drive train, and couldn't find anything wrong with anything else. Concluded it must have been a bad transfer case.

Second mechanic couldn't find evidence of metal or other signs of wear in transfer case fluid and decided to change the shift motor. This mechanic also had trouble replicating the popping noise on the less steep hills around his shop. Shift motor didn't fix it, concluded it must somehow be the transfer case.

Third mechanic (s) said it was absolutely not the transfer case, since it was totally clean of anything in the fluid (fluid was only replaced once, when the unit was first installed) and said it was almost definitely probably the hubs. They used a stethoscope to track the noise. I had to take it to these mechanics twice, as they ran out of time the first day. The first time I took my truck in to them, I had the spare tire on the front passenger's side while I was getting my normal tire fixed (drove on the spare for 5 days total). Because the spare was slightly smaller, it made the problem immensely worse (And, I was hoping, easier to diagnose). When I would have to turn, it would pop loud enough to sound like I was going to break something major. I put the regular tire back on and suddenly they could not get it to make the noise at all and blamed the tire exclusively. I firmly argued the point, having just driven down my driveway with the normal tire that morning.

So... maybe it is just another bad transfer case. I could spend the $450 and find out. No one thought the slight 2wd shimmy I have on the highway was related. Didn't notice excessive wear in U-joints. Didn't find that clunk I have in the front, either, though I suspect a mount. I'm not opposed to manual locking hubs, as long as I only have to engage them at the bottom of the driveway when I come home and then again when I leave. Same with when I'm on the farm or off-roading, etc. I find it kind of funny, even though slightly irritating, that such a big noise has eluded three mechanics.

End history.

 

[Original_Ranger84]

Well the only thing I can think of after that is that maybe the chain in the Tcase stretched when being in 4x4 and working really hard twice a day and that somehow that makes the popping noise and wouldn't leave metal shavings.

 

[mhughes165]

x2 on stretched chains in the case, its the only sound i could ever think of similar, look around online, new chains and rebuild kits are cheap

 

[Sampson]

There should be no need for manual hubs since it is a live axle setup and only the transfer case engages when going into 4 wheel drive since the hubs are always engaged.

 

[Groelzj]

My father, a farmer, welder, machinist, do-it-all kind of guy, came to visit and that's what he suggested too. It's the only thing that could "slip" without leaving big chunks of metal (gears, etc.) in the case.

We got a new chain on my father's recommendation. I haven't installed it yet, but it's on my list of things to do today...if only it would stop raining so I could work on it without getting everything wet!

None of the transmission/mechanic/4x4 guys here even mentioned the chain as a possibility...that's why I came to you fine folks online!

Thanks again, I'll get the new chain put in the transfer case this weekend when the weather gets a little better. We're under flash flood watches right now and normally that kind of work is done in the Kona sunshine.

Jon

 

[feellnfroggy]

Since noone has addressed this, what year is her truck. Auto hubs ran til I believe 96, 97-98 was PVM hubs and 98 and newer were live axle setups no hubs. I may be a year off, but either way. Use 4x4 hi for downhill, and 4lo for uphill. Its most likely just binding, tell her to take it out in a grassy field and hammer it in 4 lo. If its just binding then you wont have any popping in the soft traction ground. Sometimes even slippery gravel is to much traction for 4lo.