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Discussion Starter #1 (Edited)
** EDIT: This problem was solved! It ended up being the rear brake shoes. If you have had leaky rear axle seal(s), read on, for all of the gorey details. **

OK, I have been trying to figure this one out and have come up empty handed so far. Grab yourself a beer and have a seat... this is going to take a while :D

Here are the specs on the truck:

1998 Toyota Tacoma 4wd xcab w/115,000 miles
GVW = 5,000 lbs. + (might be a factor? don't know)
V6 - 5 speed manual/original clutch
ADD (automatic disconnecting differential) with shift-on-fly 4wd (but not push-button)
Rear factory elec. diff lock
Front ARB air locker
Stock gear ratio 4:10
Alcan 8 leaf packs w/Downey shackles and worn out Rancho RSX9000's

I first noticed it I believe about 5 months ago. It's fairly hard to describe, and seems to be more likely to happen after the truck has been sitting parked and the ambient temp. is cool or cold, and also during use of 4wd. But, it has happened many times in 2wd as well, and also when it is warm. Sometimes it feels like axle wrap. But the thing that makes me think it is not axle wrap is because there seems to be a "dead spot" or some kind of binding that happens at one spot in the revolution of the drivetrain. When the "high spot" or "dead spot" comes around, it binds up against something else, and provides a lot of resistance. It's not enough to keep the vehicle from driving (like having the parking brake engaged) but when coasting to a very slow stop, you can feel it just as the truck is about to come to a final stop - it's as though I suddenly mashed the brake pedal, and an abrupt halt occurs. Also, there is no wheel-hop or clunking when I take off from a stop (like axle wrap). Several weeks ago, I was following my friend Mark to his house, and when I was stopped somewhere along the way (traffic light I guess), I depressed the clutch pedal, and put it in nuetral, and then released the clutch pedal, and felt a prounounced "clunk". Another night, I was leaving a parking lot, and I got some symptoms - this time very pronounced, and repetitive. I was able to play with it a bit in the parking lot and get a better feel for it. I was feeling more now like the rear-end might be going bad. Let me describe what happened that night...

I got in the truck and started it. I released the parking brake and depressed the clutch pedal, put it in 1st gear. As I began to release the clutch pedal, I could tell it wasn't starting to move the truck - something felt like it was binding up. So I quit the release of the clutch pedal well before the pedal was fully up. I put it in reverse, and slowly engaged the clutch. It felt like there was more travel in the clutch pedal than there normally is for the gear to engage, but nowhere near as much resistance as I had in 1st gear.

After backing up a bit, I depressed the clutch pedal, put it in nuetral, and let it slowly roll forward (I was on a very slight grade). As it started to roll fwd, I get a "BANG" like the back of the truck got hit by something, and then it continues to slowly roll forward.

I tried it again, and backed up the truck once more. This time, I put it in nuetral and released the clutch (took my foot off of the pedal). And then I took my foot off of the brake. I was on a slight grade, and the truck should have rolled forward, but it didn't. I swung my left leg and hip outside and planted my foot on the ground and used my leg to leverage a push while my other foot remained above the brake pedal (didn't want to hit a passerby). The truck was definitely binding up. Then it slowly seemed to get past the "dead spot" and rolled freely forward.

I played with it some more in a different area of the parking lot (with some downhill grade), and got the truck slowly rolling - as I applied the brakes very slowly, and just as it was about to come to a complete stop - I got the abrupt "Bang" and felt like I got hit again. I am hanging out the driver side door, and trying to watch the driveline and rear diff, but it is difficult to do while still operating the clutch and brake. At one point I can see the whole assembly lurch when the bang happens, but couldn't really tell if the axle tubes were rotating or the springs were flexing (axle wrap). As I left the parking lot, it proceeded to do the banging thing whenever I pushed the clutch in and came to a stop (stop sign, traffic light, etc).

Fast forward a bit:

** I took the truck to my friend Mark's place on Feb. 5. **

I thought for sure when I got in the truck that morning, and it was cold, and I hadn't driven it for about 19 days, that it would be doing that "binding up" and "clunking" thing really bad. Well, guess what? It drove as smooth as could be from my house all the way to Mark's place (about a 20 minute drive with plenty of traffic stops). Geez! As a side note - a friend had suggested that I take a look at the carrier bearing on the 2-pc. rear d-shaft. I never thought of that, but it made good sense to me. I was hoping that that would be the culprit (easy fix!).

So, we put it up on jackstands. Spun everything and looked at everything, and couldn't feel that binding, or see anything that seemed wrong. I would have followed another friend's suggested method of isolation, but we couldn't get it to bind up. One thing we discovered, is that the front d-shaft does not spin when you rotate the rear d-shaft with the transmission in nuetral, and the t-case in the 2-HI position (guess I was never sure on that).

Here is how the t-case operates:

2-HI - front d-shaft does not spin, 4-HI - front d-shaft spins, Nuetral - front d-shaft spins.

Because this problem occurs with the t-case in the 2-HI position (normal driving, with the d-shaft not spinning) we pretty much ruled out the front end. But as I write this, I am having second thoughts, since the front axles do turn when the truck is rolling on the ground. (But the clunk does seem to come from the rear, so I dunno.)

The one thing that we were skeptical about, was that carrier bearing. It has a rubber donut that the bearing sits inside of, and it sure seemed to have a lot of play in it. We marked the flanges at the front and back of the d-shaft, and then removed it. We laid it up on my tailgate and inspected and greased it. The u-joints all seem just fine. The carrier bearing spun freely and didn't bind at all, or make any funny noises (dang!). So everything with the driveshaft seems fine. With the driveshaft disconnected, we spun stuff again. No binding. We noticed that there is a slight bit of play in both rear axles, when you grab the tires and push/pull really hard. The passenger side seems to have a little more play than the drivers side. The play is not really up/down or side-to-side, but in-out. The axle tube flanges are tight against the backing plates for the wheels, so no problem there. We took a sample of oil from the rear diff. and it seemed just fine. We changed the oil in the transmission, and the t-case. It was fine. No play in the pinion flange on the rear diff. No play in the output flange on the t-case. All of the rear axle u-bolts were tight.

So, we put it all back together and I backed out into the street, and proceded to put it in first and drive a little. The clunk came back! Mark heard it. He got close and tried to see what was happening, but there was really nothing to see. He also seemed to think it was coming from the rear.


We pulled it back into the garage and checked the rear brakes. They look great. Spun the wheels some more, and couldn't get any binding. Put the wheels back on, and I drove it home - never felt the clunk again. What the hell??!!!

Fast forward a bit:

** I pulled the 3rd member on Feb. 26 and inspected it. **

The 3rd member looked to be in excellent condition. And spinning the pinion by hand, everything looked great. The diff housing and oil were clean (no shavings, metal chunks). I tried to remove the actuator, so I could release the locker and spin the side gears, but the actuator didn't want to budge. I decided after talking to my friend Brian, that side gear damage was unlikely (with no evidence found in the oil or diff housing) and what was visible looked good. So I never did turn the side gears. But I am pretty confident in saying that the 3rd is just fine.

My next steps are to probably inspect the rear spring hanger bolts (found an old post on a forum where someone had a problem with those) and then maybe have a clutch job done (and consider it preventative maintenance) since I am still on the original clutch and the bearing seems to whine a little louder than it used to (it has whined since day one).

I also should mention something that has happened a handful of times (probably 4) - both before and after I have experienced the above problem. And that is that when engaging 1st gear, it does not engage at first, and then engages very violently with a "bang!". Very isolated and cannot duplicate the problem.

OK - get out your crystal ball and tell me what's wrong! Somebody out there must have gone through the same thing by now. Maybe?

Thanks!
 

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Have you checked to see if the rear locker engages and disengages properly? It almost sounds like the rear locker is not all the way unlocked and the axles are getting bound up. It is kind of fishy that the locker actuator didn't want to come off when you unbolted it. I would try removing the actuator again; it should come right off, and you should be able to lock and unlock the rear axles with a screw driver through the actuator opening with ease. This would explain the binding you are getting..........but not the "not engaging at first, and then engaging very violently with a bang". Is the bang coming from the rear end or the clutch area? If the bang is from the rear end area, it's almost got to be missing teeth on the ring gear, pinion gear or side gears. If it's from the clutch area, I would have to guess a broken clutch pressure plate. I hope this helps some, but of course I'm guessing here too. I'll talk to the rest of the ******* gear heads around here and get back with ya if I come across something. Good luck and keep us updated..............
 

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Discussion Starter #3
Hey John, thanks for your help. I just went "public" with this today, on the forums, and you are the 3rd person to suspect the rear locker. I put up some pics of the rear 3rd in case anyone wants to have a look...

http://www.bajataco.com/Rear_Diff/index.htm

"Is the bang coming from the rear end or the clutch area? If the bang is from the rear end area, it's almost got to be missing teeth on the ring gear, pinion gear or side gears. If it's from the clutch area, I would have to guess a broken clutch pressure plate."

I can't really tell where the bang is coming from unfortunately. It has been a really long time since it happened. I'm trying to remember the last time it happened, and I want to say it was last summer. Lots and lots of miles since then. Another friend has also suspected the clutch/press. plate/pilot bearing, so that could be too.
 

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After looking at the pic's, especially #8; I have some more questions for ya. Did you check the spider gears for any abnormalities? If the spider gears were to for some reason not mesh properly and you were not going perfectly straight would definantly cause binding and or popping sounds. The only way I can think they could become misaligned is a thrust washer be missing/worn or the 4-pinion shaft be worn. Are you the original owner of this truck? Has anyone been into this rear end? And if so, for what?
 

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Discussion Starter #5
John, the spider gears were hard to get a focused picture of through that small opening. As I mentioned, they were locked, so I couldn't turn them to see what all of the teeth looked like, but the ones I could see looked good. I think ultimately, I might have to just pull the 3rd again and get those spider gears moving. Yes, I am the original owner, and this is the first time the rear end has been opened up. I have had axles out on both sides to replace axle seals - but the pumpkin has never been opened before.

My friend Brian (whom I mentioned in the first post) just had a revelation regarding why I couldn't get that actuator off. A quote from him:

" Chris, as I said on the phone, I doubt the side gears are the trouble....but Tim brought up a very good point that I had not even considered. It is possible that the splined sleeve is catching on the carrier end of the locker. If the shift fork or the sleeve have worn enough, it could happen. But, just like with the side gears, you should see this while turning a corner, not travelling strait.
If you do pull the 3rd member again, be sure to pick up a new o-ring for the actuator. Yours is probably shot, and won't be usable once you pull the actuator.

Huh...you know what? ... I know why you couldn't pull your actuator......despite what I told you......you have to pull the shaft that connects the stepper motor to the shift fork....which means you have to pull the detent ball and spring out... "

I should note that this binding and clunking is happening when I am driving straight, as well as probably at a slight turn. I can't remember if it has happened during a full turn or not (it's probably pretty unusual to roll to a stop during a full turn).

Thanks again for your help!
 

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Discussion Starter #6
Hmmm... okay, I am looking at the FSM for the actuator removal and reinstall... and it looks fairly involved (at least for my limited experience with it). It's much more than just pulling the pin out, and removing the spring and ball, and reverse of that to put it back together. Crap.

Also, I have a question (getting off topic a bit here) - when removing the 3rd, you have to disconnect two wire plug connectors, and a "hose". I assumed the hose was a vacuum line and operated the shift fork similar to the ADD on the front diff. But, I see no mention of this hose in any of the e-locker write-ups, and I only see a pic and mention in the FSM to disconnect it and make sure no water (or similar) gets in the tube. What is it for? Is it vacuum? For the FSM procedure for testing the actuator, there is no mention of vaccum.
 

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BajaTaco said:
Also, I have a question (getting off topic a bit here) - when removing the 3rd, you have to disconnect two wire plug connectors, and a "hose". I assumed the hose was a vacuum line and operated the shift fork similar to the ADD on the front diff.
Hey chris,

That hose on the elocker motor is nothing more than a breather. No vacuum, no need for testing (well except if it is clogged), no nothing to worry about there.

When was the last time you replaced the axle seals? How much gear oil got on the brake shoes? A lot? If you get the shoes soaked pretty good it doesn't matter how much brake clean you spray on them, they may eventually glaze over. Its has happened to me (and dan as well). When this happens, at slow speeds you get a clunking sound - sometimes feels like someone just rear-ended you. However I think it only happens when you apply the brakes. But something else to look into.

later!
shane
 

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Discussion Starter #8
By the looks of your sign off, I'm willing to bet this is "BrusselsLace" Shane! I think the shoes are okay. But I will snap some pics tomorrow and post them so you can give your opinion. I'm not past putting on new shoes if it might cure this bizarre problem.

And thanks for explaining the tube!

THANKS! I apprecate it. See you at AZRocks (hopefully I can drive the truck there, but I will make it regardless).
 

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BajaTaco said:
By the looks of your sign off, I'm willing to bet this is "BrusselsLace" Shane! I think the shoes are okay. But I will snap some pics tomorrow and post them so you can give your opinion. I'm not past putting on new shoes if it might cure this bizarre problem.

And thanks for explaining the tube!

THANKS! I apprecate it. See you at AZRocks (hopefully I can drive the truck there, but I will make it regardless).
Like Shane said it happend to us both. Mine took some time after I did the axle seals before my rear brakes started binding. The gear oil will slowly expand the shoes to a point where they will catch early. When mine first started doing it I thought it was the tranny or x-fer case or axle also. Mine first did it on I-10 on my way to work in the morning. Scared the hell out of me!!! If your axle seals have ever leaked, You might as well replace the shoes just to be safe. BTW my shoes looked ok when I pulled them, But after replacing the shoes I have never had the problem again.
 

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Ha! same shit happened to me. That gear oil is some potent stuff.
 

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hornito said:
Ha! same shit happened to me. That gear oil is some potent stuff.
Who would have thought that gear oil on brake pads would have a bad effect on braking. :rolleyes: :p
 

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Crash said:
Who would have thought that gear oil on brake pads would have a bad effect on braking. :rolleyes: :p
nah dude, it helps. That's what they said at vatozone. :rolleyes:
 

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Yup, you found me ;) And yes, thats bear.

I like dans explanation - the shoes swell up and catch early. If they are glazed over they wil be shiney. I had one shoe that I could almost see my reflection in! ;) Come to think of it, I have been having an intermittent problem that kinda sounds like what you are experiencing. I only notice it when I am pulling into the garage and only after I had the truck parked on the driveway (doesn't happen when have been driving like on the way home from work). As I am barely easing into the garage I feel this binding in the driveline and then there is a big shuddering/bang sound. Its enough of a binding that if I slowly let out the clutch the truck won't move until it overcomes what ever is holding it back. To me it feels like the rear brakes are catching. So I thought maybe my ebrake wasn't releasing enough. I pulled both drums and everything "looked" fine. Backed off the adjusters and I can't say I have had the problem lately. BUT, I haven't been driving it as much since then either. AND, I didn't replace my shoes the last time my axle seals leaked. Hmmm.... Maybe this is a good enough excuse to go with disk brakes in the rear ;)

http://www.users.qwest.net/~brussels_lace/stuff/p6050006X.jpg
Off topic, but... The next time you replace your axles seals use this part#: 90310-50006 . Its supposed to be an upgraded seal. In the pic above, the left one is the 'stock' one and the right one is the 'upgraded' one. You can definately tell that the right one is much better. Do they actually work better? Don't know yet. I usually replace my axles seals once a year and I just put in the new ones last summer. I'll let you know next winter how they are doing ;)

see ya at azrocks!
shane
 

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Discussion Starter #15
Awesome guys, thanks for the input.

OK, here is a decision I have to make. At this point, I have the 3rd bolted back up with new FIPG sealant. I don't have the gear oil in, d-shaft hooked up, or axles back in yet. Should I put it all back together, and just get new brake shoes, and have brake service done? And see if that cures it? Or should I pull the 3rd again, and haul it to Phoenix (2 hr drive) to have someone look at the actuator and locker/spider gears? I don't know anyone around here who has a lot of experience working on those (and I don't really want to take it to the local dealer). I am leaning towards just having the brakes done locally and see if that cures it. If it doesn't, and I have to pull the 3rd again, it's just time consuming (no air tools), but not hard.

What would you do?

(note: we spun the rear tires while it was in the air, and didn't notice any binding... but it could be different when rolling on the street and applying brakes I guess. I don't think we ever applied the brakes while it was in the air).
 

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Discussion Starter #16
Shane, I guess we were both typing at the same time. Hmmm... weird that you are maybe having the symptoms again! And disc brakes - well that sounds pretty cool :) You thinking about the FROR full-floater kit?

Thanks for the tip on the seals - the one that I put in was the Timken off-the-shelf from AutoZone.
 

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Chris,

After re-reading your description of your problem and comparing it to what I have experienced as of late, it sounds to be exacly the same. I'm betting on the brake shoes, especially since I haven't really had it happen since I backed off the adjusters. When did you last replace your axle seals? Did a lot of gear oil get on the shoes?

later!
shane
 

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BajaTaco said:
Or should I pull the 3rd again, and haul it to Phoenix (2 hr drive) to have someone look at the actuator and locker/spider gears?
That to me is a lot more work than putting on new brake shoes ;) So my vote is for the new shoes. Now I know we don't all have money trees and I hate replacing stuff only to find out it didn't fix it. Replacing shoes is pretty easy, you can do it yourself (you just tore appart your rear end), and you might want to have the drums turned.

You might try backing the brake adjustors off a bit. There is a rectangluar hole with a rubber plug in it on the backing plate. Pop it out and with a little screw driver you can turn a 'cog'. I don't remember which way to turn it but the idea is that if the shoes have swelled up a bit, backing off the adjustors (allowing the shoes more room) would compensate for it. Try it and drive around for a while. If it cures it then I would say its the shoes.

later!
shane
 

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Discussion Starter #20
Okay, I looked at my records. Here is the history with the brakes/axle seals:

23,301 miles - replace left rear seal, replace oil soaked shoes

80,891 miles - brake insp/service with new brake FRONT brake pads (okay, here is where I thought I had rear brake shoes done, but looking at the paperwork, I guess not)

87,658 miles - major service done - rear brakes are listed as recommended (but looking at the service detail, I don't see it on there?! :eek: memory sucks).

89,000 miles - replace right rear axle seal and bearing

112,000+ miles - replace right rear axle seal

115,000 miles - current mileage. I am thinking I should do these brakes. I took some pics - any opinions on how they look? Now that I look at them, the left side actually looks a bit cruddy and the right side (recent oil leaks) looks clean.

http://www.bajataco.com/brakes/index.htm
 
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