82 drive train noise

[Guest simpsy82]

I've got a funny grinding type chatter noise coming from the from either the diff or tranny only when the car shifts. at first i thought it was the CV axles but after cahnging both of those i have discoverd thats not my problem. just wondering if anybody can point me in a place to start looking now. is it possible to be the drive chain on the tranny? any help would be great thanks.

[Guest pfloro]

Hello simpsy82:

Let's try to isolate the problem:

1) Do you hear these noises at ALL shift points? (1-2, 2-3, 3-4). What about at the torque converter lock-up point (about 40mph on a level road with a light throttle)?

2) While stopped, shift into '1' and drive off on a smooth & quiet road. Since the transmission will not shift out of first gear, we eliminate at least some of the transmission components. Do you hear the problem noises?

3) Repeat the above but start off in '2'. This 325-4L Hydramatic should start off in second gear and stay in 2nd (my '84 Toronado with the same trans does). Do you hear the problem noises?

4) While maintaining a steady speed (about 25mph) in '2', quickly apply a little throttle and then quickly back off completely. Do you hear the problem noises? This will provide a 'load' and 'coast' situation on the entire driveline. Excessive gear lash or other slack will come into play.

5) While in 'P', open the door & listen. Better yet, lay next to side of the car & listen. Have someone open & close the throttle a bit. Listen... Do you hear the problem noises. While in 'P' or 'N', the drive link (chain) is turning on it's ball bearing sprockets. If the chain is very slack, it will knock against the rear cover. Worn bearings will make a whirring kind of noise.

Your findings will help narrow down the problem. Having owned my '84 Toronado since it was new & driven it over 180,000 miles, I'm fairly tuned into

the entire car.

Keep us posted.

Paul

[sosuzguy]

Follow Paul's test above but yes I bought a parts car one time that sounded like a chain slipping off the shoulders of a sprocket. It had bad sprocket shoulders somewhere in the transmission.

[Guest simpsy82]

Ok let me try and answer all those questions.

1) ot only makes the noise when it shifts hard and in all gears

2)it wont make the noise in first or second when accelerating easy but if you make the 4 barrels open up it will make the noise.

4) i dont hear any excessive diff lash

5) i can only haer a faint noise if any and i dont think it is to bad probably just chain noise.

[Guest pfloro]

Thanks for providing more information...

After re-reading your findings to questions 2 & 3, a light went on in my brain!

Can you please clarify again: If you start out in '1' and apply easy throttle, no noise? If you then start out in '1' and apply a heavy throttle, the noise is heard?

Let's try one more test: Warm up the engine & trans with a short drive. Pull off the road and make sure <span style="font-weight: bold">nothing</span> is in front of you. Set the parking brake,

<span style="font-weight: bold"><span style="text-decoration: underline">firmly</span></span> step on the brake pedal with your left foot & shift into any forward gear. NOW..., press the accelerator pedal to at least half to 3/4 of it's travel.

Don't hold the throttle open for more than 5 seconds as this 'stall test' rapidly heats up the trans fluid. <span style="font-weight: bold"> Do you hear the noise?</span>

If you do, I suspect the problem is a bad torque converter. Assuming there is no slippage within the trans, the above 'stall test' locks <span style="font-weight: bold">everything</span> from the drive wheels back to the turbine within the torque converter. Unless this noise is coming from the engine itself (?), it must be coming from the converter.

That 'grinding' / 'chattering' noise could be due to damaged vanes on the impeller, stator or turbine within the torque converter. Unfortunately, the transmission must come out to replace the converter. While it's out, it's prudent to rebuild the transmission (OUCH / $$$$).

How many miles are on the car? Do you know if the transmission has ever been rebuilt?

Keep us posted.

Paul

[tim63riv]

Simpsy,

I worked as a technician at a Oldsmobile and a Cadillac dealer in the 80's. I had a Toronado with the 307 Olds engine that made a similar noise. There was a momentary clicking or ticking noise as the vehicle accelerated, and was most noticable right before the transmission shifted. Had me stumped for the better part of the morning. What was happening was unique to the design of GM's full size front wheel drive cars from 79-85. When they are accelerated, the front of the engine torques upward, not to the side like a rear wheel drive vehicle does.

What had happened was the starter drive return spring had fractured and was coiling up on to itself,reducing the spring force that keeps the starter drive in the retracted position. As the engine torqued upward, the starter drive slid down and just barely touched the flexplate, making a ticking noise! Pulled the starter, replaced a $2.00 spring and the noise was gone. Its worth a look, and the starter has to come out to remove the transmission anyway.

Also, most transmssion shops are more than happy to give you a free roadtest and an estimate on the cost of repairs. Good luck with the noise!

Tim McCluskey

[Guest simpsy82]

thanks guys. I had a mechanic take it for a drive today and he thought it may be the flex plate he said hes herd that noise before and said the flex plate was cracked and when the torque powerd up it made a grinding noise so im going to have a look under there and make shure the bolts are tight aswell. pretty shure i put locktite on them but you never know when youres in a hurry.

also can you guys tell me if the fluid in the diff is shared between the tranny? because honestly the sound to me seems to be coming from the diff. you can feel it in your feet.

thanks.

Kevin

[Guest pfloro]

Hello Kevin:

The differential oil is NOT shared with the transmission fluid. SAE <span style="font-weight: bold">80W GL-5</span> gear lubricant is specified for your Canadian climate. The transmission is separated from both the engine & the differential when it is removed.

The two transmission mounts bolt to the frame near the firewall area. Vibration can easily be 'telegraphed' into the frame, through the body mounts and into the body.

I would perform the transmission 'stall test' which I discussed earlier. Since the differential internals are locked (as well as everything from the drive wheels back to the converter turbine), the suspect noise (if heard) rules out the differential... During a 'converter stall test', the only internal transmission component turning is the pump (supplying fluid flow & pressure).

My gut tells me the noise is somewhere between the end of the crankshaft and the transmission input shaft. Your mechanic's flex plate theory makes sense as well.

You're getting closer.

Paul

[Guest simpsy82]

sorry, i guess it should of mentiond thet the mechanic did a stall test and it would not make the noise untill he let off the brake a bit and the car moved. but while the converter was torqued up it made no noise. thanks for the conformation on the diff oil.

[Guest pfloro]

Kevin:

I have more information which may be of help.

An easy way to get a peek inside the differential is to remove the cover. With the car on a lift, a helper can rotate each tire so you can at least see the spider gears turn. Check the drained gear lube for metal particles or contamination. Instead of a cover gasket, RTV silicone is used to seal the cover to the pumpkin. Fresh gear lube is a good thing too!

IMHO, the stall test confirmed that the flex plate is OK and it's attachment to both the crankshaft and the torque converter is sound. During the stall test, engine torque is being transmitted to the converter via the flex plate. If something was amiss, you would have heard the noise.

I'm still not convinced the torque converter can be ruled out as the noise source. During the stall test with the brakes applied, only the impeller (converter pump) is turning (at engine speed). When the car was allowed to move, the turbine began turning & transmitted power to the input shaft of the transmission. While turning under load, the turbine may be hitting the stator which is in between the turbine & the impeller. Since the converter also has a 'torque converter clutch' (pressure plate), it may also be involved with the suspect noise.

As Tim63riv suggested, I'd let one or more transmission shops lend an ear...

Keep digging...!

Paul