Have a 1993 Bronco Automatic, 4 WD, 5.8lt engine w/176 thousand miles. have it for 5 years, used for about 4 thousand miles mainly towing my 5600# boat very short distances (40 mi round trip).

One night after my regular boat trips, the bronco couldn't reverse the boat into my yard. It was like the gear was in Park!. the car still can go forward towing the boat but with noticeable resistance. Backwards was impossible, I thought the transmission was going to explode into tiny parts. No grinding noise, no slipping tires nothing. just the same braking feeling like when you put the car in "P" while still very slowly moving.

I changed the tranny fluid and filter, new gaskets and I did another boat trip without a problem, and i thought that was it.

Next time I towed my boat the same problem happened again.

Please note that my trip is 22 miles one way, no problems arriving at the ramp and reversing the boat trailer into the water! then my bronco cools off in the parking lot for 5-hours while boating and then i tow my rig back home. then is when the problem shows up.

THis second time I put all 4 wheels in jacks, Engine off, Neutral, 2WD High, and saw that with the engine off, i can turn l one of the rear wheels (left, driver side) forward, and some times the other wheel turns forward. some other times the free passenger side rear wheel turns backwards. ?? this depends if I am turning the wheel OR if I turn the transmission shaft.

Now if I revert the turning on the shaft, like in reverse ( I did this with the engine running and the gear in "R") the rear driver side wheel turns in reverse, BUT the passenger side wheel turns Forward!! and they looks like they are Locked! this is: I can't stop the reverse turning wheel Nor the forward turning one. Of course IF this happens while all wheels are on the ground, the vehicle will be locked since the drive wheel can not turn in opposite directions at the same time with full engine force!

I think there must be something wrong with the differential, I am not sure if this a LSD type, or not.

I have some mechanic experience mainly with very old and simple cars (Ford Falcon 1960, Jeep ****** 1951 4WD too etc) but not with differentials or complex automatic transmissions.

I plan to open the differential case to look inside, searching for broken gears, metal splinters, broken LSD clutch parts or springs etc.

So far I have not found many specific info about this car in the net (Ihave the Haynes manual though) and I don't want to take it to a mechanic that will start by swapping the transmission, 4WD transfer case and differential while I watch my hard earned money flying away.

ANy help or links to more info will be greatly appreciated.

PS: I checked the brakes and the hand brake and although they could use a repair, they are not responsible for this total "stiffness-blocked-reverse only-anchored like" behavior. Once again it is not that the carr feels like "heavy" or it is "dragging" a heavy load. It is blocked and only happens in reverse. only on my return trip. No hills, no big difference between go and return.

Thanks

 

Is your rear end a limited slip? When was the last time it was serviced?

 

I'm not sure if its a LSD or not, I think it is beacuse of the way the wheels turn in opposite direction and also both forward.
Regarding servicing, this is looks like a very abused car, since I drive it so little I must confess I haven't taken it to a mechanic and checked the lube levels on the differential when I jacked up the car and I added about a pint of hypoid sae 90 lube to the gear.

I would go under the car on the week-end and see what I can gather, perhaps take some pictures and post them here.

What is your wild guess? anything will be welcomed and considered.
thanks

 

Clutch packs in the LS diff can cause this if they bind up. Did it work okay after it cooled?

 

I'm not sure whats wrong, but you can rule out the transmission. i would do you said and pull the cover. I suspect you will find some seized spider gears or such. (they may not be laying on the bottom)

 

Yes!..no trace of problem unless i drive the car for a while again. I am pretty sure it is temperature and load related, and I hope it is not the tranny although I can very well imagine that with all the miles and neglect this tranny must be about to die.

There is also another detail I want to add now that you mention the overheating. When I pull the boat from the ramp on my way back, I use the high 4W to be safe on the ramp. I noticed when i use this, that the car feels like the brakes are a little "pressed", the car do not rolls "free". I can get down from the vehicle ant try to "push" it and I can't move it (even on flat paved terrain w/o trailer). The motor can overcome this "resistance" but no doubts having the car in High 4WD adds some load to the drivetrain and engine.

This "brake effect" persist even if I go disengage HI 4WD and go back to 2WD. To fully remove this "braking effect" I have to drive in reverse a couple feet to free the car.
I guess it is the front autolock hubs that stay "locked" while going forward in hi 4wd and perhaps some trouble with the front differential as well.

It is possible that on these two episodes I have forgotten to disengage the front hubs by doing this "reverse maneuver" after pulling the boat from the ramp. If this really happened, I reckon the 22 miles drive back with this "extra braking effect" on the old engine, transmission and differential can overheat the whole thing leading to the car not reversing when I try to put my boat back in the yard.

I like your approach on this, It makes a lot of sense to me and it relates to what might be happening here. Do you think it will be worthy to open the differential case? What should I be looking for? any place where I can look for more info or specs?
I removed the transmission shaft from the differential end in order to separate transmission and transfer case from the differential, I turned the wheels and did all the experiment I related before. What should I be looking for?

Thanks again

 

You have done the most you can do already. Next step is to open up the pumpkin. You'll be looking at the carrier, ring gear, side gears (left and right) inside the carrier. The spider gears are at the top and bottom. The cross shaft goes through it and into the carrier. This is how wheels turn in opposite directions. If it is limited slip, you will see a lot in the carrier where the metal disks set in the carrier, the clutch disks are on either side of these metal disks. What you want to look for is clutch material in the gear oil, and/or the bottom of the axle housing. I have seen a few teeth in there as well. There is a big spring that goes inside, the cross shaft runs through it. That's what keeps tension on the clutch pack.

Good luck with it.

Bob

 

Tech Page - Powertrax No-Slip Installation

Here's a link to a tear down, with pics.

Bob

 

Thank you all for the valuable information, specially to you Bob for the article and pictures.
I will start getting the truck on stands and preparing everything for the dismantling and will take some pictures etc.
I think I will start taking the cover of the "pumpkin" and check the guts... most likely will come back to the forum with my results and seeking for more help.
Thanks again
Frank, Miami FL.

 

I don’t think you’ll find anything wrong with the differential, unless something very goofy has happened with the pinion. when you try to backup does it feel like there is a load on the engine or is it revving freely like in neutral? Unless I’m missing something, the only thing that makes sense to me are the rear drum brakes binding in reverse.

 

The "brake effect" is most likely due to a sticky front driveline. How often do you actually engage the 4WD for any distance?

The ID tag on the diff. will tell you if it is an LS or not. The will be an L after the gear ratio.

Open differentials will make one wheel spin opposite direction when there is nothing to keep this from happening. I.E. the entire axle (both tires) is off the ground. This is NOT indicative of a problem but rather a properly functioning open diff.

If the problem is thermally triggered, look to your E4OD transmission. This is a common symptom of hydraulic pump failure. Transmission fluid gets hot, loses viscosity, and the weakening pump cannot keep up with the demand for hydraulic pressure under such temperatures and loads. Another possibility is a failing torque converter. This usually only happens when the pump has failed and the guts of the pump are tossed forward into the converter.

You say you disconnected the driveshaft from the transfer case and did your test of the rear diff. Have you taken a look at the output shaft on the t-case while the truck is experiencing this problem? If you disconnect the rear DS, put the t-case in 2H and put the truck in a moving gear, you should be able to watch the output shaft on the t-case spin. If it won't while the truck is experiencing this problem, your issue is not anywhere near the rear diff.

I'm with screwy on this one. Doesn't sound like rear end problems unless you have lost a brake spring but that problem wouldn't come back, you would just break something and that'd be it.

 

I will say the rear brakes may be dragging in reverse. Do you use the E-Brake. The cable may be bound up. The brakes in the rear self adjust when in reverse. Yours may be allready too tight. (they wont back off automaticly, only on) if you drive any distance, they will fade. But after you let it cool, they could lock in reverse.

This doesnt explain having one wheel turn forward when in reverse with both wheels off the ground. I can think of no situation that would cause this. Maybe I didnt read that right. You did say the trans in reverse, engine running with wheels off the ground. (and one wheel turns forward)

 

Here is the latest, I hope it will clarify some of the questions

THe codes and numbers on the parts:

The differential: S837B // 8L-55-88-3C15 (is this "L" from Limited??)
The T-Case: C153-3-1356-56 // 128613 F2TA-CA
The Automatic Transmission: HA F2TP-HA // PRA-R10 // 00077842 // BD-3C12

New tests:
Rear wheels on jacks, gears in "P" (the Drive Shaft can't rotate, which is ok) then:
turning one wheel, the other turns opposite direction. No "brake" feeling (I guess it's ok)

Same as above but Gear in "N" (the DS "SHOULD" turn free no??)
1- Turning one wheel (driver side) forward, the other turn forward and the DS turn couterclockwise (from the differential) I would say this is normal.
2- Turning the same wheel Backward the DS stops turning and the other wheel turns forward. IF I block the free wheel and continue turning the driver side wheel backward. I feel a tremendous resistance and the DS turn clockwise. I think the turning directions are OK but why the resistance?
3- Same as #2 but turning the passenger side rear wheel. It happens exactly the same.

So Far I think my DS (and T-case and tranny behind it) has no problem turning counterclockwise (forward motion) BUT when I try to move it in clockwise (reverse) there is some resistance or brake either int the T-case or in the Tranny. Remember the gears selector is in Neutral during all this. I think all parts should turn free no?

To go further (sorry for making this too long!) I disconnected the rear DS from the differential. I also removed one of the brake drums to discard the brakes (one at least).
Having the rear end of the DS in the floor and the gear always in "N".
Both rear whells turns without noticeable resistance in both directions. they behave like a LSD, they both turn forward or reverse when I turn the differential input plate.

NOW If I try to turn the DS "toward" the T-case, there is no noticeable resistance when I turn it counterclockwise (forward motion). BUT there is a big resistance and it blocks (stop) when I try to turn it clockwise (reverse motion). this is all done by hand.

I think now (although I might open the pumpkin to inspect just for the sake of it) that the differential is OK and the resistance is either in the tranny or in the T-case.

I know I am "driving" the Tranny not from the input shaft but from the output, but still I cant imagine any reason why a normal tranny and T-case might show a much larger resistance when turned by hand clockwise than counterclockwise. Am I correct here?

Regarding the hydraulic pump: I opened the transmision cooling pipes to check if it was flowing and the flow was very little. looked like when you let oil flow through a small hose by its own weight, almost no pressure, nothing like fluid was spraying over all places, way far from that.

My next step will be to take down the forward DS to isolate any problem in the front axel-auto lock hubs-differential.

After that will take down the T-case, and then (perhaps) the transmission.

Once more time keep the good advice and encouraging words comming, I really need both.

Frank

 

Sounds more and more like the suggestion that you DO indeed have an LS that the clutches are failing in is the root of the problem.

 

Greystreak:
I hope you are right so I don't need to deal with the AT, but ....
what puzzles me now is that the resistance I feel "comes" from the T-case when I turn the DS clockwise. The Diff is disconnected from the T-case. The AT is in "N" and the drag I feel turning with my hand the DS is in one direction (clockwise=reverse) only!

What is your take regarding the low pressure-low flow on AT fluid in the front radiator piping?

Thanks
Frank