Chirping/Squeaking over 20mph?

[thehellend]

I took Bacon to the mechanic to diagnose, but they couldn't find the problem. Color me disappointed. They did suggest it was coming from near the transmission, which filled me with dread. So I'm wondering if you wonderful skilled people might be able to point me in a better direction. Note: I'm new to mechanics, so talk down to me a little so I can follow along

Here's what's happening:

Edit to add: Chevy Van G20. 1986, with 109k miles. It started after I drove her back, so it's either a new issue or one that just 'woke up' again after being sat for 2 years. When I drive her at speeds of 20mph or more, I start to hear this sort of rhythmic squeak or chirp coming from under the hood. I can't pinpoint where exactly, but as mentioned above, the mechanic thinks it's from near the transmission area. They were very quick to tell me this was just an educated guess though, as it was tough to diagnose without actually driving the vehicle (and I don't pay them enough to hang on to the underneath while it's moving!)

It seems to move in time with the wheel revolutions - so it gets faster as I speed up. It doesn't change in pitch though. It is constant as long as I'm over that speed, whether I'm accelerating or braking. I had the belts replaced, and they apparently checked the U-joints (it was the desk dude who told me, "yeah they looked good" so I'm not 100% convinced he knew what was going on). I read somewhere it could be something to do with the carrier bearing yoke, whatever that is, especially as I read about a thud noise that can happen and I'm sure I heard that happen last night.


With limited experience of driving her with the issue, I think it happens at lower speeds while the engine is cold, and then reverts to the 20mph rule once warmed up. But this isn't yet proven with a good sample size of experiences.

So with this information, can any of you point me in a good direction to get this diagnosed. Honestly I'm willing to pay for the work, but I really don't want to drop another fee to hear "we can't get close enough to figure it out" - I just want to resolve it before whatever it is breaks on me. I'm of the mentality that cars don't heal, and this issue will only get worse and more expensive the longer I leave it.

Or just words of encouragement in case my transmission is about to explode on me. That'd also be appreciated.

 

[ArtW]

They could have raised it on a proper rack and run it in the air, so IMO they shouldn't have charged you for a 'non diagnosis' for this issue (in fact, IMO a good mechanic NEVER charges a diagnosis fee for failing to find a problem, I never did)
It could well be the carrier bearing, I had on go bad on my old 76 pickup
Do you have a way to raise it so the rear wheels are well clear of the ground? and I mean raise and solidly support it, like on jack-stands

 

[thehellend]

They could have raised it on a proper rack and run it in the air, so IMO they shouldn't have charged you for a 'non diagnosis' for this issue (in fact, IMO a good mechanic NEVER charges a diagnosis fee for failing to find a problem, I never did)
It could well be the carrier bearing, I had on go bad on my old 76 pickup
Do you have a way to raise it so the rear wheels are well clear of the ground? and I mean raise and solidly support it, like on jack-stands

That's what I thought - I was a little put out by it, although they did say they did a jacked up check of the vehicle and still couldn't identify.

I own two 2-ton jack stands. I've never used them though!

 

[ArtW]

You'll need wheel chocks, too
Chock the front wheels properly, raise the rear wheels, and place the rear on jack-stands so the rear wheels are well clear of the ground
Have a helper get in and run it up to squeak speed, and lay NEXT TO, NOT UNDER the van and listen
if it seems like it might be coming from the center support bearing, make a mechanic's stethoscope out of a LONG piece of metal slipped into the end of a length of vacuum or fuel hose, and touch the tip to the bearing housing, and see if you hear the squeak through that

 

[thehellend]

Ok, I just called the mechanic to see if they checked the carrier bearing, and here is roughly what he said.

He got it 'in the air' and 'spun the wheels' so he could look closely, and did not hear any noise coming from the rear differential. When asked about the carrier bearing, he said it's all housed within some cover thing, and apparently is very hard to get at. They might be able to do a visual inspection by taking the cover off, but that might not be useful in determining if there's a problem. Apparently replacing the carrier bearing is very labor intensive and could take several hours.

I wish I didn't feel like all mechanics were talking crap to me

 

[thehellend]

You'll need wheel chocks, too
Chock the front wheels properly, raise the rear wheels, and place the rear on jack-stands so the rear wheels are well clear of the ground
Have a helper get in and run it up to squeak speed, and lay NEXT TO, NOT UNDER the van and listen
if it seems like it might be coming from the center support bearing, make a mechanic's stethoscope out of a LONG piece of metal slipped into the end of a length of vacuum or fuel hose, and touch the tip to the bearing housing, and see if you hear the squeak through that

This is great advice. I'm going to see if my slightly mechanically inclined friend wants to help with this - I'm still SO SCARED of jacking up the van and then running it (I do have chocks).

 

[Gary68]

speedometer cable

 

[thehellend]

speedometer cable

Yes! Another person mentioned that on another forum (not my post) and I thought it was interesting. I will add that to the list of things to check.

 

[Ballenxj]

speedometer cable

Could be, but my guess from the symptoms described is it's likely a squeaky brake shoe. Try this to verify, bring it up to the speed that makes it squeak, then apply brake pedal lightly. If it's a squeaky brake shoe it will either change pitch or stop squeaking. Try that and let us know.

 

[thehellend]

Could be, but my guess from the symptoms described is it's likely a squeaky brake shoe. Try this to verify, bring it up to the speed that makes it squeak, then apply brake pedal lightly. If it's a squeaky brake shoe it will either change pitch or stop squeaking. Try that and let us know.

Braking doesn't change the noise at all. The noise comes on at 20 mph, gets faster as the vehicle speeds up, turns into an almost constant noise once at highway speeds, and does the same thing in reverse, with the noise stopping again once back down to 20mph. I did notice some vague quivvering of the speedometer at very low speeds too, but these did not coincide with when the squeak starts.

 

[ArtW]

Ugh, wish we lived close and I had a lift, he should have RUN the van in the air (just off the ground enough to be safe) and listened, a squeak is a squeak, it shouldn't be hard to hear if it's audible from inside
Can you drive the van with the inside cover off? or get someone else to frive it?

 

[Gary68]

if it was something hitting the mechs should of easily found it but they are probably younger and may have never seen a mechanical speedo cable,modern cars are electrical,an old mech would of recognized it right away

 

[Ballenxj]

Braking doesn't change the noise at all. The noise comes on at 20 mph, gets faster as the vehicle speeds up, turns into an almost constant noise once at highway speeds, and does the same thing in reverse, with the noise stopping again once back down to 20mph. I did notice some vague quivvering of the speedometer at very low speeds too, but these did not coincide with when the squeak starts.

Then it's likely what Gary said, the speedometer cable. That would make the needle quiver too. Easy fix, and nothing to worry about.

 

[ArtW]

So you think it's the speedo cable? I didn't think of that, myself
Ex always said I diagnose backward, start at the worst case and work toward the easiest solution lol

 

[thehellend]

Can you drive the van with the inside cover off? 

You know, I thought about this. I think I will do this next

if it was something hitting the mechs should of easily found it but they are probably younger and may have never seen a mechanical speedo cable,modern cars are electrical,an old mech would of recognized it right away

Maybe I need to go back to my old mechanic, they're pretty old

Then it's likely what Gary said, the speedometer cable. That would make the needle quiver too.

Ok, I'm going to look into unplugging it and seeing if it stops so I can isolate the cause.

Thanks everyone, I was seriously stressing when they dropped the 'possible T' bomb, but I feel a renewed strength that I might be able to fix this

 

[ArtW]

Even if it was the 'T' that's a relatively cheap n easy fix on an old Chevy van

 

[Gary68]

i'll bet Arts next paycheck it's the speedo cable and when you get yours replaced come on over and do mine

on the cheap-sometime you can lube them but usually the are damaged and starting to fray

 

[ArtW]

Hey! Bet your own paycheck, bub!   

 

[thehellend]

i'll bet Arts next paycheck it's the speedo cable and when you get yours replaced come on over and do mine

on the cheap-sometime you can lube them but usually the are damaged and starting to fray

I checked and a new one is $40. I'm lucky that I can afford such luxuries right now (although not if my mechanic keeps billing me for time spent spinning around on their office chair....!)

 

[Ballenxj]

Ok, I'm going to look into unplugging it and seeing if it stops so I can isolate the cause.

If you unscrew it behind the speedometer it will still squeak as the transmission will still be spinning the cable. If you unscrew it at the transmission, be careful as you can loose parts going down the road. Try a little lubricant down the cable from the top by the gauge. Some recommend oil, some recommend graphite. Ask your more mature mechanic.