[slaga]

1989 Bronco XLT
351W
C6
BW1356
Manual locking hubs

First time (about a year ago):
I used 4L to pull a boat trailer out of my back yard. When I was done, I put the transmission into "N" and shifted the transfer case back into 2H. When I was backing up my drive way, the transmission/transfer case quit sending power to the rear wheels for a moment and then grabbed and barked the rear tires.
Second time (Couple of months ago):

1. Anytime the Bronco is under acceleration, everything seems normal.
2. If the transmission was put in reverse, you would hear a horrible grinding noise and the vehicle would just roll forward as if it were in neutral.
3. Anytime I was traveling faster than 20 mph and tried to decelerate, I would hear the grinding noise and it would just keep rolling as if it were in neutral. Then I would press the gas pedal to raise the rpms and the vehicle would jolt when the rpms of the engine caught up with the wheel speed.
4. In park, the Bronco would not roll forward (just like it is supposed to do) but it would roll backward just like it was in neutral.
5. The best way to describe what was happening is something in the drive train was acting like a 1-way bearing. a) As long as the engine was trying to push the wheels forward, everything was normal. b) Under deceleration, the engines rpms would drop to an idle, the vehicle would coast as if it were in neutral, and the transmission/transfer case would grind. If you gave a little throttle, the engine’s rpms would catch up the rear end and jolt the vehicle. c) If you put the transmission in reverse, you would here the grinding noise and the Bronco would roll forward as if it were in neutral.

When the owner of the transmission shop tested the transmission/transfer case, all of the symptoms were gone. The transmission shop drained the transmission and the transfer case and found pieces of plastic and metal in the transfer case fluid and the nothing bad in the transmission fluid. They replaced the shift fork and the fluid and said all else was in perfect working order.
Third time (last week):
I was driving to work going about 40-45 mph when I felt the transfer case / transmission pop a couple times under deceleration. Then, as I was driving it yesterday, the Bronco started that same grinding noise under deceleration. I pulled into the parking lot, where I was headed, and parked. I left it for a couple hours. When I got back in I shifted into 4H then back into 2H, and then drove home without incident.

Does anyone know what could cause this intermittent problem?

 

[Steve83]

Is your RABS light on? Did they check the rear diff oil for metal? Did they replace the fluid pump in the t-case or secure its tab? Have you checked the trans fluid level?

Only a bad park pawl in the trans would allow the wheels to move while in P, but it wouldn't affect any other shift position.

I think the problem is in the transmission.

 

[kf4amu]

1. Anytime the Bronco is under acceleration, everything seems normal.
2. If the transmission was put in reverse, you would hear a horrible grinding noise and the vehicle would just roll forward as if it were in neutral.
3. Anytime I was traveling faster than 20 mph and tried to decelerate, I would hear the grinding noise and it would just keep rolling as if it were in neutral. Then I would press the gas pedal to raise the rpms and the vehicle would jolt when the rpms of the engine caught up with the wheel speed.
4. In park, the Bronco would not roll forward (just like it is supposed to do) but it would roll backward just like it was in neutral.
5. The best way to describe what was happening is something in the drive train was acting like a 1-way bearing. a) As long as the engine was trying to push the wheels forward, everything was normal. b) Under deceleration, the engines rpms would drop to an idle, the vehicle would coast as if it were in neutral, and the transmission/transfer case would grind. If you gave a little throttle, the engine’s rpms would catch up the rear end and jolt the vehicle. c) If you put the transmission in reverse, you would here the grinding noise and the Bronco would roll forward as if it were in neutral.

When the owner of the transmission shop tested the transmission/transfer case, all of the symptoms were gone. The transmission shop drained the transmission and the transfer case and found pieces of plastic and metal in the transfer case fluid and the nothing bad in the transmission fluid. They replaced the shift fork and the fluid and said all else was in perfect working order.
Third time (last week):
I was driving to work going about 40-45 mph when I felt the transfer case / transmission pop a couple times under deceleration. Then, as I was driving it yesterday, the Bronco started that same grinding noise under deceleration. I pulled into the parking lot, where I was headed, and parked. I left it for a couple hours. When I got back in I shifted into 4H then back into 2H, and then drove home without incident.

Does anyone know what could cause this intermittent problem?

I had symptoms #1, #2(but only once that I remember), and #3. Not to the extent as in losing reverse, but it progressively got worse.

I learned to drive with 2 feet, since positive torque eliminated the noise.

After motor and tranny replacement, I still had the problems. I thought it might be rear end or t-case. Took it to a shop, they immediately said T-case.

Here's what they found.

smashed/ground up oil pump housing (every time you get on and off the gas, this part moves ever so slightly...its jammed against the inside of the case. Over time it wears the aluminum away and it spins. Perhaps it gets jammed in one direction but can spin in the other.

Speedo gear, the clip that held in the cable had fallen out and got ground up. This is pretty much destroyed.

After a round of parts washing, still ground up metal in the corners. The magnetic collar (only on electrics) was blistered from the gears spinning on it and required replacement.

I'm gonna go out on a limb and disagree with Steve83, I'm sure I will regret this since he's never wrong, but the similarities between your and my problems are too great to ignore

 

[slaga]

Is your RABS light on? Did they check the rear diff oil for metal? Did they replace the fluid pump in the t-case or secure its tab? Have you checked the trans fluid level?

The RABS light comes on at start up to let me know it works and then goes out just like it is supposed to do. It never stays on. The rear diff oil was not checked. The fluid pump was replaced. I don't know if the fluid pump tab was secured or not. Can this be checked without opening the transfer case up? I plan to check the transmission fluid this evening.
I spoke to the owner of the transmission shop and he wants me to bring it back to him and let him look at it under warranty. We'll see.

 

[87EBBronco]

Sounds to me like your oil pump in the t-case is spinning. The big weak point in the BW 1356. Somewhere on here is a good thread on t-case rebuilds. When you do rebuild it make sure that your tcase oil pump is secured to the housing somehow.

 

[Ubermich]

If that bracket (that is a bracket in the pic above, right?) was starting to go, could it potentially do the following:
While everything is cold everything is normal...
After driving for a while, stop the vehicle, put it into Reverse and hear a loud *thud*, put it into drive, *thud*...
All U-joints have been replaced and the rear drive shaft is not moving in this process... So could it be that piece in the transfer case is bending back and forth? :\

 

[TTBlows]

All U-joints have been replaced and the rear drive shaft is not moving in this process... So could it be that piece in the transfer case is bending back and forth? :\

No, not really like you're envisioning.

I can't make sense of all your symptoms, half of them make me think tranny while the others could be t-case.

I guess I'd pull the t-case since it's not that hard to do and open it up to look for problems, if nothing else because the t-case is easier, cheaper and more DIY friendly to service.

 

[slaga]

If that bracket (that is a bracket in the pic above, right?) was starting to go, could it potentially do the following:
While everything is cold everything is normal...
After driving for a while, stop the vehicle, put it into Reverse and hear a loud *thud*, put it into drive, *thud*...
All U-joints have been replaced and the rear drive shaft is not moving in this process... So could it be that piece in the transfer case is bending back and forth? :\

I had a "clunk" (technical term) going into reverse from the time I purchased the Bronco until the fluid pump and shift fork were replaced in the transfer case. It only "clunked" going into reverse and never in drive. When I got it back from the shop the clunk was gone. That symptom has not returned.

 

[Ubermich]

No, not really like you're envisioning.

I can't make sense of all your symptoms, half of them make me think tranny while the others could be t-case.

I guess I'd pull the t-case since it's not that hard to do and open it up to look for problems, if nothing else because the t-case is easier, cheaper and more DIY friendly to service.

I'm planning on pulling the T-case and performing a check-up on it probably next weekend or the one after, so I guess I'll find out then? My tranny is slipping, so I wouldn't doubt that some of it would come from that, but the clunking existed before the tranny started slipping...
Regardless, I figured I'd look into the transfer case since there's really not much left for the tranny to do except die :cry

I was just curious if that piece ever bent before it broke or if it was one of those things that waited to snap on you until the most inopportune moment...

Edit: and slaga, mine goes both ways, but only when hot.

 

[kf4amu]

Make sure you update the thread with your results (and pics).

 

[Steve83]

...Steve83...he's never wrong...

:histerica :lolup :histerica :lolup :histerica :lolup :histerica :lolup :histerica :lolup :histerica :lolup :histerica :lolup

 

[slaga]

Partial Update:
Sorry no pictures because the transmission shop is doing the repairs under warranty. There are pieces of the plastic from the shift fork that they replaced in the fluid (transfer case). They are pulling out the transfer case as I am typing this and will open it up to see if there is any other carnage.

Steve83, what would the RABS have to do with this?

 

[Steve83]

Nothing directly, but if the noise HAD BEEN from the rear diff, it's likely that the worn steel would build up on the magnetic RABS sensor, and trigger a fault. So an ABS light would have suggested a rear end problem.

But since the noise isn't from the rear diff, it's moot now.

 

[slaga]

smashed/ground up oil pump housing (every time you get on and off the gas, this part moves ever so slightly...its jammed against the inside of the case. Over time it wears the aluminum away and it spins. Perhaps it gets jammed in one direction but can spin in the other.

You are correct Sir. The outer case of the transfer case is worn down which allowed the fluid pump to spin in one direction and not the other. They are replacing the fluid pump and the shift fork. They are also securing the pump housing to the case by drilling a hole through them, threading the aluminum case, and putting a bolt in. Does this sound like the proper fix? Are there any other questions I should ask?

 

[Steve83]

Yes, that's the upgrade they SHOULD have done the first time around.

 

[kf4amu]

:chili: :chili: :chili: :chili: :chili: :chili: :chili: :chili: :chili: :chili: :chili: :chili: :chili: :chili: :chili: :chili: :chili: :chili: :chili: :chili: :chili: :chili: :chili: :chili: :chili: :chili: :chili: :chili: :chili: :chili: :chili: :chili: :chili: :chili: :chili: :chili:


WOOT WOOT WOOT WOOT WOOT!!!


Some people, instead of bolting it in, have welded a 1-2 inch piece of metal round bar that fits in the slot. This spreads the force of the housing moving back and forth over a 1-2 inch length instead of the 1/4 inch it is stock.

I WAS RIGHT! MUAAHHAHA EVERYONE BOW DOWN BEFORE MEEEEE

:rockon :rockon :rockon :rockon


Ok I'm back to normal now.

 

[slaga]

Yes, that's the upgrade they SHOULD have done the first time around.

That is exactly what the owner of the transmission shop said. He said that the tech that worked on it originally has already been let go. I should get it back tomorrow.:chili:

 

[slaga]

Only a bad park pawl in the trans would allow the wheels to move while in P, but it wouldn't affect any other shift position.

Forgive my ignorance, but could the spinning fluid pump allow the vehicle to roll backwards while it was in park? If not, I might be in for more trouble down the road, unless I was mistaken.

 

[Steve83]

No.

 

[slaga]

If the transmission was put in reverse, you would hear a horrible grinding noise and the vehicle would just roll forward as if it were in neutral.

Just to update. I have had no more problems:chili: since the shift fork was replaced and the fluid pump was replaced /secured to the case housing. They also adjusted the transfer case linkage. You know how when you shift the transmission into drive or reverse, the shifter falls into a "groove". The transfer case never really felt that way before they adjusted it. It does now though.
From the quote above, I know this was true because I had my wife get into the Bronco and put in reverse while a friend and I pushed that beast back out of a parking space. The repair to the transfer case fixed all of the problems listed in the original post. How could replacing/securing the pump to the housing, replacing the shift fork, and adjusting the transfer case linkage fix the reverse problem?