Thunk

[James Morse]

Thought I had this truck totally sorted but per usual nothing happens that easy.

This isn't something I noticed when looking at it. I noticed it the other day then this morning it seems like it's getting worse (louder) but now that I'm testing it maybe I'm just noticing it more. My gut feel is it's getting worse, could be wrong.

If you hold the brake and put the truck between D and R, each shift causes a thunk, or clunk, or poink, it's coming from the rear, and I'm taking a wild guess that there is play where the driveshaft hooks to the rear differential. But that's just a wild guess hoping for something not complicated.
It's pronounced and unmistakable and consistent and reproducible.
Ways to further diagnose?

 

[superj]

u-joint at the driveshaft where it hooks to the diff. put the truck in neutral and lock the parking brake and lay under the truck and twist the driveshaft by hand. see if there is play at that back u-joint

 

[Shran]

Could be a lot of things - slop in the rear axle, bad u-joint, slip yoke on the driveshaft, carrier bearing on the driveshaft if you have one, idle speed too high and slamming into gear, broken motor mount or transmission mount.

 

[James Morse]

I don't see any play at all from the driveshaft to the U-joint. Even if I try to hold the U-joint and turn the driveshaft, I get zero play there.
The play is downstream of that and I can reproduce the noise just not loud. The noise seems to come from the differential.
The amount of play is on the order of a handful of mm. Judging at the holes, or bolts, in the U-joint, at that point it's moving maybe 3mm (1/8")tops but not more than that. It's not very much.

Interesting what you said about the idle. Usually I warm the truck up, this morning I was just pulling out of the shop with it cold. I looked at idle speed cold and it starts 1400 then settles out after a few seconds around 1250. That's just running it like 30 seconds.

Then I warmed it up, so idle around 850 or so. Guess what - no noise. When you shift to D or R, with your foot on the brake, which is normal way to do things, rpm's drop to 700. You feel that you have shifted because of course the tranny is trying to go and you are loading it. But as to clunk, no, or, maybe sometimes very tiny.

This explains why I never paid it much heed. Normally the truck is warm so it either doesn't do it at all or it is so small you would tend to wonder, but discount it. I've only had it a month. I had to order parts and put them in. And since I was working on rad, I'd warm it first and check for leaks. And then the weather was cold, so I warmed it in the driveway. Just haven't had that much experience driving it yet!!

It also explains why there were in fact occasional times when I'd hear it going out of the driveway cold then shifting to D and I started thinking, is something moving in the suspension? (been there, done that). But then I'd never hear it again (because truck was warm later).

DIdn't check motor/trans mounts yet, kind of don't suspect them, but will check.

So............. should I stop worrying, if it doesn't get worse, when truck is warm? Should I be worrying about something wearing out in the diff/axle etc? Or is it all normal for truck w/ this miles (125k)?

 

[James Morse]

PS The '99 B3000 does not do this when cold (or warm) and it has 185k miles. I think it's a different differential, but probably they are "about the same" inside. Just saying.

 

[sgtsandman]

I'm leaning toward the slip joint in the driveshaft binding. Lubing it seems to have fixed similar complaints in the past for others. I don't remember the details on how to do it since I haven't had to do it myself yet.

 

[Josh B]

When you start asking questions about the center bearing, remember it's called just that. Something about Ford's transmission being given a carrier bearing and the driveshaft bearing got the shaft

 

[oldgeek]

each shift causes a thunk, or clunk, or poink,

Well, which is it? I've learned from Andy Griffith that it is important to know just what the sound is.

 

[lil_Blue_Ford]

FWIW, it’s not at all hard to remove the driveshaft bearing and two-piece driveshaft and replace it with a single piece. The bearing was going out on my 92 and contributing to vibrations so I pulled the two piece shaft, bearing, and the bearing mounting bracket on the crossmember. Being the 92 is an extended cab 6’ bed 4x4, I got a one piece shaft out of a newer Ranger similarly equipped and bolted it right in.

 

[don4331]

A 25 year old lsd could have really worn clutches; and when clutches are really worn, the carrier gears no longer mesh tightly, allowing slop in driveline when shifting into gear as a door #3 issue.

If you jack up one rear wheel, (wheels cocked, transfer case in 2wd, transmission in neutral, parking break off) can you spin the wheel and reproduce the issue?

 

[scotts90ranger]

Yes, if this is a limited slip and the other wasn't, the one with the limited slip will have more slop in the differential, it's just how it is, clutches are probably warn but not the end of the world... just refrain from doing burnouts and cookies for hours at a time and it'll last for quite a while longer

 

[James Morse]

I'm going to look up about the slip joint. Noise still there, no different. Warm idle is fine, it's like 650-700. It's like something have some play in it but still chasing it.
Driveshaft has a sticker on it check this out maybe it's not original driveshaft.

 

[superj]

i believe you are right

 

[James Morse]

And I am wondering why would someone replace the driveshaft. Truck always lived here, so, I don't think it went to that shop, I think that's a sticker on a part. But I could be wrong. The pic seems to imply, this is stronger than original.
I'm not saying noise has anything at all to do with driveshaft/u joint it was just weird I never saw this because it must have been turned upside.
Even if let's say it broke, which seems unlikely, why wouldn't the owner not have put a Ford part on it - if what's on there isn't Ford and I don't know how I'd tell.
Looks like they are still in business maybe I write to them and ask them if they have record but probably it was before computers they would never be able to find it.
Clutch & Driveline Rebuilder, Supplier, Remanufacturer - Fort Wayne Clutch & Driveline

 

[James Morse]

They can't track if work was done there without previous owners name I don't have that. Then can't tell from pics is it a repair they did or was it parts ordered online.

They said this:

"As for the clunk noise – double check the uj’s and make sure you do not see major wear/rust coming out of the cap areas. If they appear ok – the only thing left is the slip/stub near the rubber boot. You can press up/down in that area and see if the shaft is really loose. If it is = that may where the clunk is coming from.."

"You may have to drop the shaft out to work the joints by hand and see if they are free or “binding” up."

By "the only thing left" I think they mean the only thing left that has to do with the driveshaft.