Rear Differential Problem on 1987 2WD Toyota PickUp

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

…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.”

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.

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?

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…

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!

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.

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…

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

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…

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

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.

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).

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!

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

Make sure the brake shoes return to rest on that top pin when the brake peddle is released…A wheel cylinder can seize up, allowing a rear-facing shoe to remain in contact with the drum. When the drum rotation direction reverses, that shoe can self-energize, be pulled into the rotating drum…Nice pix…That is indeed a standard differential.

Your step by step plan to isolate the problem is a good one…

…and the suspense mounts.

But no answer yet. :slight_smile:

Hey Guys, I’ve been a little under the weather and didn’t feel like laying down on the cold garage floor for the last couple of days, so no movement. I had to order a new diff gasket anyway and figured I didn’t want to put it together without one just for that test in case it turns out to be a brake problem and then I have to bench press that huge chunk of metal in and out of the housing yet again. Especially since after I’ve slept on it, Caddyman’s seizing brake cylinder thought is gaining more traction in my imagination. Looking back it would have been good to have actually watched the brake action with the drum off and maybe a sticky piston would have surfaced.

OK, I’ll be back in a few days probably.

~Dan

Take your time…And use a floor jack to lift that pumpkin back in…

Hi Guys, I bet you thought I fell off the planet. Sorry for the delay but with being ill and other family urgencies, I finally got around to dealing with the truck. And then it took two weeks to get up the courage to write this. So here it is. I’m an idiot.

After finding a used diff for $150 like the tranny guy told me to do, I put it all together and what do you know, same problem! AHHHHH! Rolled the truck up and back, locking up, and took notice of the front wheel. It looked like it was the front locking up now. So I jacked it up and sure enough, it was the front! One of the caliper bolts had fallen out, the bottom one, so when the wheel turned in reverse, the caliper could rotate and jammed the wheel.

My own fixation on the rear was misguided as I associated the “reverse” problem with something in the drive train. But I guess what really threw me off completely was the tranny guy when he had it up on the lift. He said he could feel it catching in the diff. Well, the bolt was $1.50 from Toyota and I got two cuz I figured that other one had gone through a lot of stress with the wheel lock-ups.

Well, I have a spare diff now; in 15 years when I need one, I won’t be able to find one so I’ll just keep it in the shed.

Thanks guys for all your help earlier. I guess I learned to check all the wheels regardless of where I think the problem is coming from.

Take care,

~Dan

Thanks for coming back and closing out your thread…