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grotflo

Transmission growling on deceleration

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Wondering if anyone else has had this problem.  I've got a stock 4-speed with a pretty new clutch and T/O bearing.  When I start the car, it sounds normal, but as the engine and tranny warm up after a few minutes of driving, it makes a rattling noise from what I think is the front of the transmission.  Almost like metal balls inside a metal container.  When I accelerate, it seems to get mostly quiet (or maybe it's being drowned out by the engine noise).  Then when I decelerate (in any gear) between 3500-2000 RPM it makes a loud metallic growling noise.  I jacked up the rear and tried to recreate the sound, but it didn't work.  It must need the load of slowing down on the driveline.

 

It's only been making this noise for a few weeks.  Transmission mount is good, giubo (guibo?) is good, diff and tranny both have fluid, car shifts fine.  Other than the noise, all seems to be in order.

 

The only thing I can think of is that several months ago, I swapped in a Wallothnesch upgraded radiator, which is slightly thicker.  To get enough clearance for the fan, I pushed the engine and tranny back as far as I could, maybe an additional 1/4".  I've read you need to push the diff toward the front of that car, otherwise it will make weird noises, but is it possible to be under too much compression?  Or is it just an internal issue with the transmission?

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By pushing the engine/transmission rearward in order to obtain clearance for the fan, you may have introduced excessive axial load on the output flange/shaft of the transmission through the driveshaft, thus accelerating wear on some transmission components.

 

1/4 inch does not sound like much however and it does not feel that the system is that unforgiving. If you kept the differential in the same place and moved the transmission back by 1/4 I would think the center driveshaft bearing would suffer first.. or something else.

 

However there are many sources of strange rattling noises in these cars, have you climbed underneath and checked shift tower bolts, etc.? I would also check transmission fluid too - change it if you haven't, replace with good quality gear oil and check the transmission plug for any excessive, non uniform, shavings when you drain the old. This is an excellent way to evaluate transmission health (you can also have old oil sent out for testing).

 

Someone on the board (Toby comes to mind) will likely have more to say on this, and possibly personal experience with something similar.

 

HTH,

 

Jason

 

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8 hours ago, grotflo said:

Wondering if anyone else has had this problem.  I've got a stock 4-speed with a pretty new clutch and T/O bearing.  When I start the car, it sounds normal, but as the engine and tranny warm up after a few minutes of driving, it makes a rattling noise from what I think is the front of the transmission.  Almost like metal balls inside a metal container.  When I accelerate, it seems to get mostly quiet (or maybe it's being drowned out by the engine noise).  Then when I decelerate (in any gear) between 3500-2000 RPM it makes a loud metallic growling noise.  I jacked up the rear and tried to recreate the sound, but it didn't work.  It must need the load of slowing down on the driveline.

 

It's only been making this noise for a few weeks.  Transmission mount is good, giubo (guibo?) is good, diff and tranny both have fluid, car shifts fine.  Other than the noise, all seems to be in order.

 

The only thing I can think of is that several months ago, I swapped in a Wallothnesch upgraded radiator, which is slightly thicker.  To get enough clearance for the fan, I pushed the engine and tranny back as far as I could, maybe an additional 1/4".  I've read you need to push the diff toward the front of that car, otherwise it will make weird noises, but is it possible to be under too much compression?  Or is it just an internal issue with the transmission?

Mine has the same rattle in neutral only. I have not noticed a decelerating growl though.  The rattle is much quieter when I press in the clutch and go into any gear, It actually almost disappears. I was told it was the TO bearing but I changed that as well as pilot bearing, clutch, and pressure plate when I rebuilt the motor... Rattling is still there. The only thing I didn't change was the tranny itself. I finally found what I'm being told is a non crunchy 2nd gear synchro 4 speed that I'm changing in a few weeks. The rattle is driving me nuts so I really hope this replacement tranny solves my issue. Good luck with yours.

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14 minutes ago, ingramlee said:

Mine has the same rattle in neutral only. I have not noticed a decelerating growl though.  The rattle is much quieter when I press in the clutch and go into any gear, It actually almost disappears. I was told it was the TO bearing but I changed that as well as pilot bearing, clutch, and pressure plate when I rebuilt the motor... Rattling is still there. The only thing I didn't change was the tranny itself. I finally found what I'm being told is a non crunchy 2nd gear synchro 4 speed that I'm changing in a few weeks. The rattle is driving me nuts so I really hope this replacement tranny solves my issue. Good luck with yours.

 Wouldn't be the TO bearing if the sound goes away when clutch pedal is pressed. When clutch pedal is pressed (i.e., the clutch and flywheel are physically separated) the TO bearing will spin instead of the transmission input shaft. So, if growly + rattling when transmission in neutral and clutch pedal is not pressed, it is something else in the system, most likely a transmission bearing somewhere that has given up, or close to giving up, the proverbial ghost.

 

If you are changing the transmission anyway then you will likely no longer have this sound (of course new sounds may emerge)! If you drain the oil on the old transmission first, take a look for bits of bearing or gear just to get a feel for what was going on.

 

The absolute best thing you can do for a non-filtered transmission is change the transmission oil frequently. Keeping that normal wear created metal fragments out of the oil (aka, grinding paste) and stops the transmission from wearing prematurely. Of course, this is really only impactful if you drive your 02 like you would a normal modern car, with normal car miles. Driving it 1-2k miles a year means it will last quite a long time...

 

Jason

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I have a similar rattle, but only in gear and not in neutral. Like the OP, mine 'goes away' as I go faster, but I also think the engine noise is just drowning it out. 

 

My clutch, TOB, shifter rebuilt...all replaceable parts are new. All oils are new. Argh.

Car drives like a dream though.

 

If this is my only complaint, I guess I can live with it. It's not really noticeable, except by me.

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NYNick... Thats funny that our rattle would be the exact opposite. Like yours everything is new on mine, including changing the fluid every 6-12 months. I too cant complain as the car really runs/drives really well, except a recent steering wheel shimmy that I'm trying to track down with new rotors, pads, bearings. Next is the steering linkage but first I think im going to have an alignment as the front tires were worn horribly on the inside before I rotated them to the rear.

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Check your front bottom tranny cover plate if it is still there or if your using one. This cover is sheet metal half moon shape that fits on the bottom of the front tranny and secured by 10mm bolts. Sometime they can come loose or come in contact with the flywheel thus making the described noises on different operating conditions.... mine was like that.... good luck....

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