924Board.org

[positivesale]

I can't find any information on the symptoms I've noticed. I searched google for a few hours - usually I find results. I can't find info. I'm hoping someone here has had experience or can shed the light.

Here's my question regarding transmission troubleshooting, or torque tube, cv joint etc.

When decelerating heavily (engine braking, like down a steep hill) and the transmission is noisy, what does this mean? When you accelerate hard, or accelerate .. the noise goes away. I do have the sound mats out of the car, and the noise is loud. When I feather the throttle I can hear it louder. When accelerating hard I can't hear it.

All the info I can find about transmissions is "the car makes noise when accelerating". But it seems I have the opposite problem. The noise is bad feathering the throttle, and really bad when decelerating.

I will do the regular - change the oil, check oil level etc. but this transmission is bone dry on the outside, no leaks at all.

On front wheel drive cars CV joints make noises when under load and it's a rattle per revolution. This noise I have is constant loud transmission noise - just sounds like you have your ear rammed right up against the tranny, and there's no cover on the tranny. All noise is coming from the back of car - definitely not a clutch or anything near there. It does sound very like you have sand inside the tranny instead of oil. But then when you put the pedal down to accelerate at a medium load, goes away..and also goes away under heavy load.

Other notes:
-Taking car out of gear stops the noise immediately
-Noise occurs in ALL gears, not just some
-Noise occurs at ALL speeds, slow or fast.
-Excessive noise ALWAYS noticed when decelerating.
-NO noise in neutral. NO noise when stopped or idling. NO nosie when clutch pushed in.
-Gears shift great. No problems. No grinding at all.
_________________
82 931

[924RACR]

I had a similar aggravation with my 82. Was concerned about it, naturally - although I should mention that it was really only when hot that it was bad.

Removed the trans, got new diff bearings (which is what I thought it was) and took it to a fellow PCA member who knows his way around trannies. We removed the diff cover to inspect. Bearings and gear teeth (ring and pinion) looked fine. He said don't worry about it.

So I refilled it with fresh synthetic gear lube (Redline) and didn't.

Sure, change your oil, don't be surprised to see some sparkly stuff, that's not abnormal, and make sure you put a good synthetic back in. I use Redline (www.redlineoil.com), MTL90 is what they recommended for this trans. A lot of P-car owners like Swepco too.
_________________
Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

[positivesale]

Thank you. I will change the fluid today if I can get those drain plugs and fillers off with a few homeade 17mm bolts and nuts. Otherwise I'll have to order or find one of those tools or buy one if I can find it at the stores here.

So did you find that the fluid was low or thin? I'm guessing the thick stuff is a good sound barrier, and hopefully mine is just thinned out.

I think I will put dino oil in first, to confirm the tranny is ok and flush it out. Then if the car is good to go I'll spend the 500 dollars on the synthetic oil
_________________
82 931

[positivesale]

I drained it and i couldn't find one bit of metal in the fluid. I squished the oil through my hands with gloves on, and no bits showed up. Suprising... Looked at the bottom of the pan and no sparkles at all.

The fluid was dark in color, and smelled like transmission fluid (good thing, hahaha). The new stuff I put in was light in color..and the car still makes about the same noise as before. Maybe the sound mat in these cars really does make a big difference. I threw mine out. Uh oh. Are any of the spinning wearable parts inside the tranny not metal?
_________________
82 931

[Paul]

Does the noise change if you do "S" turns while decelerating?

Have you checked your tranny mounts?

[positivesale]

Good call! maybe it's just vibrating and enhancing the noise through the hollow fuel tank and body in there.. I'll try that.. doing some really tight S-curves and hairpins. I think i'll go take a drive right now.

It changes a lot when I go down hills, ,when more load is on there. And there are some really tight turns on the hills downtown here, so I'll give it a good run for it's life on the sanfransisco like hills. If the rubber is shot, then the noise would vibrate in there pretty bad in that BIG hollow area, and cause my loudness problem...

After changing the tranny fluid, the car was harder to shift.. so the stuff I put in must have been too thin.. was dino stuff. So I'll have to research the thicker brands (don't know if synthetic will be thinner??).

Thanks for the pointer and we will soon see.
_________________
82 931

[MAAS]

My 924S did this too. My mechanic told be that:

a) all of these trannys are fairly loud anyway.

b) the torque tube amplifies the sounds from the tranny.

c) the noise (under deceleration) was most probably from one or more of the output bearings in the tranny. This is why your tranny shifts fine, and why the gear oil change won't make much difference.

However, (according to my mechanic) if it is the bearings, it's no big deal unless they get very loud.

-MAS

[positivesale]

Thanks MAAS. It's good to hear that these trannies are a bit loud. I did also rip some of the foam out that's above the fuel tank. I do have an idea.. I will put in spray styrophoam around the area above the tranny and insulate it. That will help with the sound. I will try to make a sound mat for the trunk too. The tranny doesn't bother mee too much, but it's almost loud enough so that it could disturb a conversation when going down a hill. (not that anyone is driving with me that much anyway, but still.)

I did take it for a drive, and going around corners didn't change the sound much. I'll check the bushings by hand though.. hopefully they are thin or worn, and I know for sure the foam will stop a lot of noise. I don't know how bad it really is though.. if I'm covering up the sound or if this is just the way these trannies are.

I suppose if there was no metal in the fluid though.. what type of bearing is the one you are talking about, do you know? Like if it was going bad, would it put metal pieces around do you think? I don't expect you to know for sure, but if you have any thoughts let me know!
_________________
82 931