Good morning, hope everyone had a good weekend.

Have been driving (yes, really) the '73 1.7 FI car, honored my daughters request to be dropped off at school in it today.

Hoping to get some help on a rotating noise from the rear of the car, it's been there since I got it running and not gotten better / worse.

It starts as soon as the car is in motion.
Applying the brakes doesn't change it
Sound is proportional to the car's speed
Sound doesn't change when the car is cornering
Sound isn't dependent on what gear I am in (gearbox the correct amount of oil)
Sound isn't there in neutral when car is rev'd

That to me suggests axles need attention, but wanted to check in and see what you all think.

Thanks!

I'd start by jacking up the car and rotate each wheel. You should then be able to narrow down the cause of the sound.

the fact that the noise goes away while coasting in neutral means that it is inside of the transmission


quote name='Tdskip' date='Feb 25 2019, 10:48 AM' post='2692103']
Good morning, hope everyone had a good weekend.

Have been driving (yes, really) the '73 1.7 FI car, honored my daughters request to be dropped off at school in it today.

Hoping to get some help on a rotating noise from the rear of the car, it's been there since I got it running and not gotten better / worse.

It starts as soon as the car is in motion.
Applying the brakes doesn't change it
Sound is proportional to the car's speed
Sound doesn't change when the car is cornering
Sound isn't dependent on what gear I am in (gearbox the correct amount of oil)
Sound isn't there in neutral when car is rev'd

That to me suggests axles need attention, but wanted to check in and see what you all think.

Thanks!
[/quote]

He didn't say "noise goes away while coasting in neutral"

He said "Sound isn't there in neutral when car is rev'd"

We don't know if the car is in motion when rev'd.

Is it Skip?
I would do as Stephen said. Check brakes for debris/wear

Thank you for all the responses, sorry if I wasn’t clear enough.

The noise is not gearbox related because it occurs if the car is in motion regardless of whether the gearbox is engaged, the clutch is in or out, and it’s independent of the gear that I am in.
It is road speed, not gearbox rpm dependent.

My guess is it is CV. Is it a click sound?

Bob B

first check is....rear wheel bearings and axles

can you sort of describe the sound in words here...like low or high pitch...grinding...etc

Could be the Differential.
Which is ...
wait for it...

In the transaxle.

The noise is more of a swoosh rather than a click. Not a grinding noise or rumble.

George-sorry if my response seemed a bit short, trying to make to make sure it’s not gearbox is obviously a very important consideration, I probably should’ve written “ I don’t believe it’s gearbox related because ...”, Hope that didn’t come across the wrong way.

Got the car in the air, rear brakes are dragging some. There is some tension on each side and you can hear a dragging noise when I rotate the wheels by hand.

For some reason I find that I have to adjust the clearance on the rear calipers more than I think I should (and always adjusting them out away from the rotor). The car sits a lot without being driven, but I don't know why that would make a difference.

One of the backing plates is bent and making contact with a rotor?

Ohh, good question. Let me check.

Clever idea, but the backing plates look OK. OK as in not bent or anywhere need the rotor and straight and attached properly.

Can you produce the sound? Engine off, jack it up and spin each tire by hand.

Hi. When I do that I only feel drag from brakes and sound of the brakes dragging. Hard to spin them over quickly enough to simulate road speed. Doesn’t sound the same but that might be speed based.

Check tightness of stub axles ?

if the sound starts when the car is in motion and in gear and when taken out of gear, still in motion the sound goes away, it is in the transaxle

Hi George - did some more testing and it turns out I have two sources of the noise,

With the car moving at under 30 mph but in neutral and shut off I hear a rotating noise that I think is the brakes dragging. Pretty sure my rear calipers are stuck from sitting and that part of the noise doesn't change when I apply the brakes because the rear calipers aren't doing anything.

I also hear a separate noise at higher speeds that goes away when the car is put in neutral.

Ok so you take your daughter to school and later discover your rear calipers are not working.

What do you think the next move will be?

Every time I end up getting rebuilt rear calipers along with all the caps,seals, and parking brake cables in order to properly lassemble, lude, and adjust them to where they work properly and don’t drag. It’s always best to have your brakes and tires be the safest part of a car, ok fuel system too. They pose the most risk to your life.

Can you isolate it to one side? Wheel bearings?

I’m skeptical that the brakes could be dragging such that at 30mph you could hear them. I would think they’d have to be dragging pretty hard. If that’s the case they should be plenty hot after driving just a little ways. Either way, adjust them so they are set up properly.

The noise you hear at higher speeds that goes away when you shift into neutral is your transmission. If it’s noisy in 4th/5th it’s likely your intermediate bearing. Ask me how I know.

...and do what DD said- make sure your cv bolts are tightened to spec with the proper tool (not allen bolt unless they’ve been replaced). Check the inner and outer cv bolts on each side.

The car stops fine for around town low speed use, I'd venture to say that I am far from the only 914 owner who drove a car with seized rear calipers without realizing it.

They will be replaced, obviously.

Let's keep this cooperative please.

Me too, I think that is very low speed. Brakes not hot after use so scruffing off pad material but not anywhere near locked up.

Let me check the noise level again because it is most noticeable at low speeds and hard to hear once up to speed.

Is there a specific gear I should try to isolate the noise in? I ask because in other cars some gearboxes have a direct gear that can be used to help isolate issues.

Thanks for the help.

venting clearance on calipers, adjust the calipers.

Corrosion on the CV boot flange and inside the trailing arm axle pocket ?
Or junk in there like a long string wrapped around or a rock?

Thank you for all of the responses and suggestions.

Just had a break in calls so I did some more testing and I actually have three distinct noises;

1) brake rotors and pads, will address, not a source of concern at this point
2) first gear is definitely noisy and has a distinct sound compared to the other gears
3) once underway and out of first gear ( it’s in first gear that I get that sort of whoosh noise I described earlier, it’s not present another gears) the sound is more of a rumbling, so I think it’s a bearing.

It’s also worth noting that if I am at speed in 2-5th gear and then take my foot off the gas the noise goes away, it immediately returns once the car is under engine power again. So car in gear and at speed but no accelerator pressure equals quiet, as soon as I have pressure on the gas pedal equals noise.

All possibilities of one several or all together...comorbid:

1. Broken or worn transaxle carrier bearings.

2. Worn Gear stack components.

2. Low oil in Transaxle.

3. Worn CV's or not serviced.

4. Bad rear wheel bearings and bushings.

5. Although not likely given the description of symptoms...tire noise.

6. Incorrect vent clearance at rear calipers or warped rear rotors or out of spec rotor.

if the car makes the noise in gear while driving and goes away when the car is out of gear and rolling down the road, there is something going on inside the transmission

Tell her take the school bus home

Rob and gentlemen -thanks for the details responses.

The gearbox is properly full with the correct oil with only 50-100 miles on it, but when I double checked it today it was already dirty and had grey material in it. Tires are new and balanced on straight rims, and I run these tires on another car so I'm familiar with how the sound.

Out the transmission will come.

I drove mine for a while like that if it is the tranny.. what about the CV's those are easy.
I'd pull those and inspect and repack.

Just pull the stack first if you suspect the tranny.

I just sold my spare. John Larson built it. Brand new cryoed bearings....they were $800 friggen dollars. Just drive it till it breaks if your having fun...just make sure the brakes work well.

Good morning, thanks for all of the coaching Rob.

I'll check the CVs just in case, easier than trans rebuild for sure.

If it is the bearings and I keep driving it how much risk of damaging the rest of the box?

If it is a 1.7 there isn't enough horsepower to probably shear the cage the rest of the way and grenade everything.

That thing can whine as it wears for a very long time.

I'd do the CV's and the rear bearings before I'd yank the trans.

Do all the rear suspension rehab work including the calipers and you will never have to touch it again except to adjust the venting clearance.

Thanks Rob, Will follow that coaching /path

Hi guys, hope everyone is having a good weekend.

Follow-on question - I noticed today that the engine does not make that noise when in reverse. Is that expected?

Just curious what, if anything additional, that helps diagnose.

Thanks!

Reverse is on the coast side of the ring gear, this would point at a final drive issue

Thanks Dylan. So consistent with the prior thoughts....