Help diagnosing a "thump"??? (1 Viewer)

[ashooter]

1992 FJ80 I just bought - very nice rig, BUT...

When you're sitting at a stoplight, in gear with your foot on the brake, SOMETIMES (not always) when you let off the brake and just start to roll forward, there's a "thump" that sounds/feels like it's coming from underneath... I don't think it's the brakes. Might be the transmission.

Transmission shifts smooth and perfect as you speed up. Doesn't hesitate going into drive or reverse from park.... there's just that "thump". One other '93 FZJ80 I looked at did the same thing.

Is this a big deal??? Anybody know what I'm talking about?

 

[tarbe]

Pull your driveshafts apart, clean the splines, re-grease.

Or, at a minimum, shoot grease into your slip yoke zerk until the shaft just starts to move (go slowly, not like you are killing rats).

Greasing from the zerk would only get rid of my clunk for a short while. Pulling them apart and cleaning/re-greasing was much more effective.

I use moly fortified grease in my slip yokes...same stuff I use in my birfs.

btw: this is a common issue, discussed extensively on the forum.

 

[baxter650]

Check the bolts on your control arms, i had one come loose that made a clunk on accel.

 

[ashooter]

Thanks guys. Another guy pointed me to this thread -
https://forum.ih8mud.com/showthread.php?t=22649

GOOD INFO!

Hopefully I can figure this thing out. I am a complete newb when it comes to Cruisers, and not much of a mechanic... But I can see from the little time I've spent poking around here that there are a lot of knowledgeable people to tap into for info.

 

[ashooter]

ONE OTHER QUESTION:

I noticed in the thread I referenced above that the yokes on the front drive shaft should be 90 degrees to each other, not both aligned the same, as are the yokes on the rear drive shaft. Mine are not 90 degrees -- the front and rear driveshafts are the same.

I assume this could be causing the "thump"???

If so, a question to illustrate what a non-mechanic I am:

How do I get the driveshaft off and the u-joints back "out of phase"? Just unbolt the "flange yoke", pull the whole u-joint with the dust cover off the shaft, turn 90 degrees, and slide it back on?... (after cleaning and regreasing, of course)

 

[tarbe]

How do I get the driveshaft off and the u-joints back "out of phase"? Just unbolt the "flange yoke", pull the whole u-joint with the dust cover off the shaft, turn 90 degrees, and slide it back on?... (after cleaning and regreasing, of course)

You got the idea. I don't think that is causing the "thump" though. Might cause a vibration.

It is not uncommon for the uninitiated to put both shafts in-phase. We've seen that more than a few times by folks who don't work on cruisers regularly.

 

[4WD Toyota Owner Magazine]

ashooter, i just had my front driveshaft balanced and they put it together in phase, thinking that before it was wrong (90-degrees out of phase). To answer your question, to have it done right you can't just pull it apart and put the yokes out of phase. You should really take it to a driveshaft shop, tell them firmly that yes, it's supposed to be out of phase, and then have it balanced. That'll alleviate worries of future vibrations or problems with it.

You might think about putting in new U-joints at the same time. Toyota spiders are about twice as much as those at NAPA, etc but MUCH better built--tighter tolerances, etc. They're about $67 each or so, need two per driveshaft.

Dave

 

[ashooter]

You got the idea. I don't think that is causing the "thump" though. Might cause a vibration...

So, my best bet is to take the sleeve yoke off and clean it, and the splines, and then regrease? I haven't noticed any "vibration", but this is the first Cruiser I've driven more than about 10 minutes...

Only thing is the "thump" I get when I let off the brake at a stoplight or something like that. Transmission shifts fine accelerating all the way up to 70mph. Brakes feel fine. Only thing I can think of is to drop the shaft(s), relube, and get those front shaft u-joints lined up 90 degrees out of phase.

Any other stuff you guys think I ought to check while I'm crawling around under there?

Also -- If it's not as simple as just realigning the the u-joints, would it be foolhardy to try that first and then worry about balancing the drive shaft only IF I get some kind of vibration? I don't want to cause a bigger problem by half-assing a fix for this one.

 

[tarbe]

So, my best bet is to take the sleeve yoke off and clean it, and the splines, and then regrease? I haven't noticed any "vibration", but this is the first Cruiser I've driven more than about 10 minutes...

Only thing is the "thump" I get when I let off the brake at a stoplight or something like that. Transmission shifts fine accelerating all the way up to 70mph. Brakes feel fine. Only thing I can think of is to drop the shaft(s), relube, and get those front shaft u-joints lined up 90 degrees out of phase.

Any other stuff you guys think I ought to check while I'm crawling around under there?

Also -- If it's not as simple as just realigning the the u-joints, would it be foolhardy to try that first and then worry about balancing the drive shaft only IF I get some kind of vibration? I don't want to cause a bigger problem by half-assing a fix for this one.

If the splines grab when the shaft tries to change length, you get the clunk, thud, thump or whatever you want to call it.

I personally would not balance the shaft before doing the PM and getting the joints back out of phase.

 

[ashooter]

Can I drive with one driveshaft?

Now that I have the front driveshaft off, can I drive it around with only the rear without hurting anything? Ditto if I drop the rear and reinstall the front?

I'm hoping I can see if the "thump" goes away with either driveshaft out, in order to isolate where the thunmp is coming from.

Just FYI - the sleeve yoke was pretty dry and sticky on the outside, but looked like just about the right amount of fairly clean looking grease inside (on the splines) - slides easily on and off, with no hint of "hydraulic lock". Could the black gunk on the outside of the sleeve yoke cause this kind of thump sound?

I will clean it up, put it back 90 degrees out of phase like it's supposed to be, and take it to a shop to make sure it's balanced... then work on the rear driveshaft.

 

[CJF]

Ah. You have a 92. You need to be clear about this in your threads: different engine, different tranny, different quirks. (Edit: You were clear in this one, but not your other current thread that led me here.)

See this:

https://forum.ih8mud.com/showthread.php?t=82229&highlight=clunk

Honestly, other than routine maintenance issues (driveshaft re-greasing, etc.) I'd accept it as normal.

Curtis
91FJ80

 

[CJF]

ONE OTHER QUESTION:

I noticed in the thread I referenced above that the yokes on the front drive shaft should be 90 degrees to each other, not both aligned the same, as are the yokes on the rear drive shaft. Mine are not 90 degrees -- the front and rear driveshafts are the same.

I assume this could be causing the "thump"???

If so, a question to illustrate what a non-mechanic I am:

How do I get the driveshaft off and the u-joints back "out of phase"? Just unbolt the "flange yoke", pull the whole u-joint with the dust cover off the shaft, turn 90 degrees, and slide it back on?... (after cleaning and regreasing, of course)

I wouldn't do that. My 91's front DS is in phase, and I'm 99% certain that's how it's supposed to be. I really think you're not getting the correct info for your year in this thread. (No offense to anyone, of course.)

Curtis

 

[ashooter]

Dang.... Now I am confused:

https://forum.ih8mud.com/showthread.p...ighlight=clunk

So, is the front driveshaft on a '92 supposed to be in phase, or 90 degrees out of phase??? Seems to me that it shouldn't hurt anything, and might be a good idea, to put it 90 degrees out.

Am I wrong?

 

[Romer]

You can get Toyota U Joints from Crusierdan (check Vendors section) for a big discount than from a local dealer. They are better. Take these U joints and your drive shaft to a drive shaft shop and have them replace them and balance. I also have a discount with a local Toyota dealer (thru my club) so to do one shaft, Toyota U Joints and balance was $195.

I recommend doing both shafts, one at a time. Have the spilne cleaned and re-greased while your doing it.

 

[CJF]

So, is the front driveshaft on a '92 supposed to be in phase, or 90 degrees out of phase??? Seems to me that it shouldn't hurt anything, and might be a good idea, to put it 90 degrees out.

Am I wrong?

My FSM shows it in phase. I'm also pretty certain (but not 100% positive) that my front shaft has never been removed, and it's in phase.

Would it be a good idea to change it anyway?? I dunno; try it and report back if you like.

Good luck,

Curtis

 

[ashooter]

How bad is a "bad" u-joint?

After cleaning up my driveshaft and u-joints, I noticed that the u-joint with the sleeve yoke seems to have a little bit of a "sticky" place when you swivel it around. Doesn't feel loose, just doesn't feel "right" when compared to the rear u-joint. My question is: Can/will I screw up the front diff or the transfer case if I put the driveshaft back in with a bad u-joint?

I'm going to order some new u-joints for the front DS from c-dan, but want to drop the rear DS first and see what the u-joints feel like there first. Might be another week before I get around to it... Should I just drive it around as a 2WD until then?

Also, just FYI - I drove it around a little bit today with no front DS and the "clunk" is GONE. So, it was either comeing from the u-joint itself, or from the sleeve yoke hanging up on the splines.

 

[CJF]

Can/will I screw up the front diff or the transfer case if I put the driveshaft back in with a bad u-joint?

No. You might blow out the U-joint (not likely in a week or two), but you won't hurt anything else.

I drove it around a little bit today with no front DS and the "clunk" is GONE. So, it was either comeing from the u-joint itself, or from the sleeve yoke hanging up on the splines.

Woah there. More likely it was coming from all the accumulated AWD slop, both front and rear. If you think about it, all you've eliminated is it coming solely from the rear end. It could still be from anywhere in the front, or (again) a mix of front and rear slop accumulating at the t-case.

Not trying to be a spoil sport; just telling it as it seems to be. Feel free to let me know if I'm wrong.

Cheers and good luck,

Curtis

 

[ashooter]

Roger that CJF - There is a lot more stuff moving/turning/cranking/flexing in front of the TCase than just the front diveshaft.

I guess I should've said, "I HOPE the thump/clunk was coming from the front DS... it seems to have gone away when the front DS is gone."