Rear Differential Problem on 1987 2WD Toyota PickUp

toyota
trucks

#1

A few weeks ago I started to notice that my 1987 Toyota Pick-Up Truck (22R engine, short bed, 2WD, 5 Speed, 205K miles…named “The General T” after the famed Charger featured on the 1970’s TV show “Dukes of Hazard”) wasn’t always rolling freely on inclines (such as when I was at a stop light), and sometimes there was even some noticeable resistance when backing-up out of a parking space – but this condition always quickly went away, and I was off to motor happily. Thinking it might be a sticky brake caliper, I got a brake check at a local shop. The brakes checked-out okay, but the technician (who knows these trucks and has even owned 2 of similar vintage) said it was a problem with the rear-end differential. [I had sort of suspected this before I took it in, but didn’t want to bias his diagnosis.] With the truck on the lift, he demonstrated how if he rolled the driver’s side wheel forward several turns and THEN rolled the wheel backwards that it froze-up. [Not a hard clanging, noisy, metal-on-metal stop, but sort of a “binding” stop.] If the wheel was then rotated forward just an inch or so, it would then rotate freely again, both forward AND backward past the point where just seconds ago it was “stuck.” Huh? The above condition did not present itself on the passenger’s side. The differential is a “limited slip” type – or so I was told by a friend who gave it to me 5 years ago after we pulled it off a junker truck that he had had that itself had like 250K miles on. The technician suggested that the internal clutch plates (which negotiate the torque distribution between the wheels, as is my understanding) might have worn – given all the miles and wear. The “U Joint” checked out OK as well. So, my question: Is there anything really, really UNSAFE about this worn differential…assuming its the internal clutch plates that are worn. Could it be anything else? Can I just put this problem in the category of “Another annoying thing about a 20 year old vehicle”? It’s winter now, but in the spring (when it gets warmer) I’ll be in a bit better situation to go to a junk yard and swap in another differential…in fact this was on my “to do” list anyway, as I want to experiment with another gear ratio to improve fuel economy. Could the cold weather have made this problem evident? I don’t recall anything like this in the fall. Any other quick diagnostic tests I might be able to perform? I don’t really drive very far from home, and I always carry a cell phone and my AAA card, so I have no real concerns about being inconvenienced: I just don’t want to be driving down the road and having the whole differential pack-up as if someone had slammed on (and locked-up!) the rear brakes. Thoughts?


#2

Well, first off, the 1970 Charger on ‘Dukes of Hazzard’ wad the General Lee. You,know, like General Robert E. Lee. And secondly, if the problem in the differential is in the limited slip or spider gears, the your in luck. The rear axle is similar to the Ford 9" rear axles like they still use in NASCAR. The center unit ‘pumpkin’ that houses the pinion, ring gear, and spider gear arrangement is removable, and easy to work on on a bench. All you need to do is slide the axles out on both sides just enough to disengage the gears in the pumpkin, and unbolt the pumpkin from the axle housing. Then, take the pumpkin to the work bench, and fix the gear unit there. Or swap it out with a unit from a junkyard that has been inspected.


#3

The rear brakes are drum type, there are no calipers to check back there…I suspect a brake shoe is dragging, (broken or weak return spring, partially stuck wheel cylinder, e-brake cable stuck). Far more likely than a differential problem. Pull the drums and make sure the brake shoes are returning to rest on their pins when they should be. Don’t be afraid to clean them up with a water hose or pressure washer so you can see thing better…


#4

I’m having the same problem. The brakes and U-joint check out okay. I removed the prop shaft and rolled the thing backward and sure enough, clunk and differential locked up. If it is worn clutch plates in the diff, where exactly are they located? I ask because I found what I think someone’s calling the “pumpkin” online and am wondering if this will fix my problem. Here’s a link to it. http://www.autopartswarehouse.com/sku/Toyota/Pickup/Lock-Right/Differential/1987/Base/4_Cyl_2-dot-4L/PTX1620-LR.html?loc=Rear
Apparently it is not everything that is in the rear end but if this has the clutch plates in it, I’ll go with it. Thanks in advance for your help.
~Dan


#5

If you replace the “pumpkin” you will replace the entire differential…Be sure you get the same gear ratio that you have now…The first step is to pull both axles out about 10 or 12 inches…


#6

Thanks Caddyman. That sounds easy. Is that the “pumpkin” that you’re talking about, in the link above?


#7

…because it says it is not the whole diff. Stated: “Replaces the spider and side gears only; The rest of the differential gears are not included with this item as it retains the OEM ring and pinion setup for easy installation.”


#8

It’s most of the diff. The ring and pinion setup are the input gears, and they’ll stay in the housing once you remove it (the housing) from the rear axle. There’s a preload that needs to be done to those, so if you don’t have to mess with them, it’s easier.


#9

Thanks chaissos. I’m hoping that I definitely don’t have to mess with the gears. So are those clutch plates included in that part already?


#10

Yes… The “Pumpkin” is the entire differential unit and gear-set. You pull the axles out, drop the driveshaft, remove the nuts or bolts (about 10 or 12) that retain the pumpkin in the housing. You should know that very few Toyota P/U’s of that vintage had a limited-slip differential so it will be more difficult to find one and you will pay considerably more for it…


#11

Thanks. I’m working on taking it out now.

Do I need a limited slip diff? I hardly use the truck actually, just in case I need to move a piano or something!


#12

You might. check and see if the axle shafts and the ring/pinion setup are the same. I would guess there are slight differences that will require the same spider assembly.

Depending on cost, you may want to consider just swapping the entire axle with one from a yard - if, of course, you can find one. Some calls can answer that for you. It’ll be more work, as the brakes, etc will have to be moved. But if you really don’t need the limited slip, and the replacement unit turns out to be expensive… Something to check into, anyway.


#13

Well now I’m really baffled. The pumpkin looks nothing like the photo in the link above. There is some semblance of form to the center part which has the differential gears, but that whole thing is attached to a “hat” with a large 43 tooth ring gear bolted onto a flange on one side, which is driven by the pinion. The problem is all the gears look pristine with beautiful witness marks where the wear ought to be and nothing is damaged, loose or missing. The oil was clean coming out. Furthermore, there is no clutch whatsoever in this thing, unless it is updrive of the pinion (buried) and I rather doubt that. Bearings all in tact and smooth. Very little backlash but I can feel some. All splines are clean. I’m having a hard time understanding what could be wrong with this unit and especially believing that there is a clutch assembly in there at the moment. Going to sleep on it…


#14

See if you can upload a picture or two on Photobucket, or wherever, and link to them here. May help…


#15

The “clutches” are right in the center section and they tend to lock the spider gears together so BOTH axles must turn when the pinion gear is rotated. If the carrier rotates freely when the pinion gear is rotated while holding one axle gear stationary, that’s a standard axle, not a limited slip…Pumpkins are more correctly called “Third Members” …

A broken brake return spring or an incorrectly assembled rear brake can cause the problems you are having…


#16

OK, here are photos.

I see now that the middle part (containing the differential gears) is what is in the link above, but I don’t believe that is what I need. I suppose that item is oft damaged and in need of replacement but mine looks perfect. I also don’t see how to attach the ring gear to it which is what threw me, but in any case, I think that’s not my issue. If you cannot see what you need and would like any particular close-ups, please let me know. Can you confirm that there are no clutch plates by the pics? After that I don’t know what could be wrong with this rear end. Thanks for looking.

~Dan


#17

Caddyman, thanks for the explanation. Now I know I wasn’t missing something obvious regarding the clutch plates. I’ve got a standard axle. That only confounds the troubleshooting now since I don’t even have what has been assumed to be wrong.

I am revisiting the rear brake idea. Having disassembled them to pull the axles, I noted that nothing was damaged or missing. I have had these apart several times over the years and believe I am competent enough installing them and have been the only one installing them since the truck was new. I’ve got 60kmi on the shoes and they still have a lot of life left. I appreciate the thought about a broken spring but they are all good.

However, in spite of the investigation so far uncovering no smoking gun, I plan to do the following tomorrow. (Having eliminated the tranny by shaft disconnect, it’s got to be either the rear end or the brakes.)

  1. Reinstall the pumpkin with half the nuts and without oil.
  2. Reinstall the axles.
  3. Leave brake shoes out when putting wheels back on. (Sounds really safe, doesn’t it? :slight_smile:
  4. Push vehicle backward to the same degree previously required to replicate problem. (That’s one thing I have to say about this, at least it is consistent. There’s not much more frustrating than to have an intermittent problem, don’t you think?)

Depending on the results, the rear brake should either be implicated or absolved.

Thanks for joining in with me, Guys.


#18

Be sure and check the axle bearings while you’re there. You have to take the shafts the rest of the way out, but you’re almost there now (unless you did remove them completely, instead of the normal 6" or so). You may have a roller bearing that is catching and binding (although that’s really rare).


#19

Thanks for that. Ya, the shafts are out cuz I figured may as well check the splines and see if there was anything in the tubes, but I didn’t want to pull the bearings if at all possible. I did think about that but the thing rolls forward without issue, and, get this, it stopped the truck flat while rolling backward down my 15° driveway at about 5 mph, which I think one bearing couldn’t do (that’ s a heck of a lot of momentum to lock up under), but even if it did, I can’t imagine it happening without sustaining a whole lot of damage that should be noticeable when rolling forward or spinning free. Nevertheless, if I run out of ideas, I should keep that one on the list; just don’t have the stinkin’ SST’s for it!


#20

I have to admit, that diff looks pretty clean, but if you’ve done what you said you were gonna do, it’s go to be in there. There’s simply nothing else connected.

Normally, if the bearings are an issue, you’ll see it as soon as you pull a shaft. Needles will be all over, as the bearing would have mostly fallen apart by then.

Chase