I am experiencing this annoying thud in the rear of my 1998 4runner when I release the foot brake from a stand still. It occurs more so when I'm on a downward slope. I first thought it was my spare tire somehow moving, but its not. I dont know whether it is my brakes or something more serious. Has anyone else had this problem? There are only 75k miles on the rig. Any help would be much appreciated.

 

It could be the U-joints in the rear drive shaft, check them and while you're there shoot some grease in all the fittings.

 

I would bet that you have an axle seal leaking into the rear brake drum. Pull your drums and check. The thud that you hear is the shoes becoming unstuck from the grease on the drum.

If you dont regulary grease your driveshaft you should, lube keeps things from rusting and wearing out.

Good luck!

 

Grease your rear driveline at the slip yoke thoroughly also check the upper and lower bolts on your pan hard bar...mine loosened a bit and caused the bar to shift under load.

 

my money is on the axle seal or the brake cylinder in the drum....ive had the same problem.

Mine still do it b/c i had some junk on my drums...just need to take it off and spray degreaser on it

 

Thank you for all your help, I will definitely look into all of what you have said.

 

Might also be axle wrap if you have worn rear shocks. That is that was doing it to my forana.

 

Most likely it's dry slip yokes in the drive lines. You're supposed to lube the u-joints and slip yokes at each oil change (You HAVE read your maintainence booklet, yes?), but lots of dudes don't know this or don't bother. This is the usual outcome, and a classic 4Runner problem.

First, your truck is 4WD, right? If not, the cause lies elsewhere, as 2WD trucks don't need this.

Go to your local good auto parts store and get a grease gun and good-quality NGLI-2 grease that contains Molybdenum Disulfide (MO2s). Valvoline makes an excellent synthetic grease with moly disulfide that's readily available.

Jack the truck up so all four wheels are off the ground. Put it in neutral so the drive shafts can be rotated. Crawl underneath and get the grease gun ready. You'll find grease fittings at each end of both drive shafts, six in all. The fittings in the centers of the u-joints are for the u-joints. Give these a couple of pumps until you see old grease start to squeeze out of the joint. The fittings on the outside of the u-joints are for the slip yokes. These need lots of grease, like 6-8 pumps. Don't do more than this at first, as too much grease can "hydrolock" the slip yoke. Put the truck back on the ground and go drive it. You may need to repeat the greasing of the slip yokes if the problem isn't fixed. Trust me, the clunk will go away as soon as the grease gets distributed throughout the slip yokes.

At each subsequent oil change, repeat this and you should have no further problems. My '98 stayed clunk-free after I initially fixed the problem when the truck was new.

Best regards.

 

My bet would either be axle seals (pull drums to verify) or sticking driveshaft joints (slip joint is most common problem...so lube all zerks anyway).

 

Thanks for the detailed description Karl and thank you Jamie.

 

Well, after I had my slip yokes greased the thud has officially gone away!!! Thank you everyone for your help.

 

Glad you got it fixed!

 

I posted on another thread with this same topic... I should have searched

Can anyone explain how the slip yoke is malfunctioning due to lack of grease to cause the "clunk"?



Erich

 

x2...

 

The lack of grease increases the friction in the slip joint of the driveshaft. So now that is requires more force to get it to move, when it does let go it has alot more force behind it and thus the audible "clunk" sound.

 

This was a great thread and hit the nail on the head with my problem. I have had the "clunk" as well and had my mechanic father in law take a look at it. He said that it was either the joints needing to be greased or the axle seals leaking into the drum just as has been mentioned here. Sure enough we opened the brake drum and there was some grease build up on the skids.

I plan to put it up on the lift this weekend with him and grease the joints and also replace the axle seals. Could anyone help me with a couple things to make sure I get the right parts etc...he lives an hour and a half away and there is no toyota shop out his direction at all so I have to get all the stuff before I go out:

My truck is a 3.4 99 4runner:

1. Is there somewhere online I can get a diagram of the rear axle assembly?

2. I believe there is an inner AND outer axle seal in that assembly. If it is a leaking axle seal do I need to get both or just the outer seal? Are these "simple" to replace? I think if my dealer told me right they are about 15 bucks a piece.

3. What kind of grease and or oil solution should be used to refill the axle assembly?

I know he may know a lot of this (father in law), but I want to make sure I am as set to go as possible when I get out there on Saturday to make the most of his time and get the correct fix and cover all bases.

Thank you!

 

the haynes manual helped me out alot for the rear oil seal fix

 

To theryanator:

There are quite a few great write-ups around here. Searching for real axle seal should net you some pretty good stuff. Also, search for threads started by JasonB, as I recall his thread about it was pretty good.

The problem is actually with the inner axle seal, but that's a good thing. The outer seal I believe is pressed in with the bearings and would require disassembly of the hub (sucky). Again, there are some pretty good write-ups around on this.

Here's how the process basically goes (I've done it before):

1. Take off the wheel.
2. Disconnect the emergency brake on the back of the hub assembly.
3. Disconnect the brake line and figure out some way of stopping flow.
4. Take off the brake drum (can be troublesome...get a rubber mallet or some sort of beating device).
5. Take off the four bolts on the back (inner) side of the hub assembly (these are holding the hub to the axle).
6. Pull the hub/axle out. This thing is a little heavy but can be done by one person. Try not the scrape anything as you pull it out. You can just set this down with the axle pointing straight up.
7. You'll see the axle seal, as it's pretty obvious. Before you go destroying it look around and see if you can find where the hole is.
8. Remove the axle seal. This can be a pretty big PITA as you want to be very careful to not scrape or damage the axle housing.
9. Put the new axle seal in. You're going to wanna get it all the way in. When it seats you should feel it. This is also kind of a PITA.
10. Put everything back together (axle/hub in, bolts, brakes lines, drum, wheel).
11. Bleed the brake.

Some other tips:
- 3rd Gen rear axles use 80W-90 GL-5 gear oil. I'm not sure about other models.
- You will want the inner axle seal and the axle o-ring. When you find a diagram somewhere around here you'll see what I'm talking about.
- Having a lift will probably make this easier...except getting the axle in and out. It's not exactly light.

Hope this helps.
-Beau

 

This is the part that drove me NUTS when I replaced mine!! I couldn't for the life of me figure out what to use to stop it. Any suggestions? I tried paper towels, Q-tips, even chewing gum I just ended up sticking it in a can and going as fast as I could while checking the reservoir. They should include a little cap in the kit for brake jobs so you can keep it for later

Erich

 

i just used an ole regular clear flexible aquarium tubing, put that on the end of the brake line and then clamped it, works pretty good if you can find the right diameter tubing