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Oh, trouble, trouble!!! Diagnosticians needed...

maestromaestro

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#1
So, I now have an issue and I can't quite pinpoint it. The sounds is almost like clatter/grind, it is quite loud at low speeds - but, it only manifests when 1) the transmission is engaged and 2) I am on the gas.
It gets more pitchy as the throttle gets more open, but if I press the clutch pedal in, it disappears. If the car is sitting idling in neutral, the sounds is *still there*, but softer. I put her on the lift and used the mechanics stethoscope to listen for things in the engine bay and underneath while it was running with cruise control engaged.

The sound is loudest (can be heard without the stethoscope, really) at the transmission end (driver side). Everything else underneath is relatively quiet. But, in the engine bay, the stethoscope picks it up the loudest at the "fuel rail" (the thing that can be seen in the picture).
I am inserting the link to the sound file as well (this one I recorded IN the cabin, while driving - so, hopefully it can be heard even with the road noise and other noises that the intake and the BOV make)

Sound file.

Could really use the "swarm knowledge". People talk about DI chatter, but this is way beyond this, and, as I note, it is quite apparent at the transmission case.
 


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#3
Here I am! Thanks to Erick_V for the mention and thanks to maestromaestro for reaching out. So upon listening to the sound file, reading your description and looking at the photos, I will say it sounds nearly exactly like the issue that I had. The culprit in the end was the input shaft bearing, which is located just on the other side of the cover you took a photo of. Doing my own diagnosis, I did the very same thing that you did. Had the car up on jack stands, ran it, put a little load on it with brakes & gas and used a stethoscope to pinpoint the noise. Same exact spot. It's very loud and crunchy when you use the stethoscope! SO - I would recommend starting there and having it replaced. (You can buy a kit with both input & output shaft bearings; PM me again for sourcing parts help if interested.) This will require pulling the trans, opening it and replacing two easy-to-reach bearings. When I did my rebuild, I replaced everything. The output/input shaft bearings are easy to get to and replace so it would be pretty straightforward to do in a weekend if you are comfortable with this sort of thing.

I don't know why it would sound the loudest at the fuel rail. Perhaps it's how it is connected to the block or maybe there's a bracket that touches the trans. You may have other issues, too. And, as an aside, all of the oily residue on your trans - I had that too. It's trans fluid leaking from the seal around the trans gearshift housing assembly. There's a small o-ring and a lot of surface area there. On mine, a good bit of corrosion had caused a leak. I used some very careful cleaning there with mild steel wool to dress it and put plenty of trans fluid & silicone paste there to prevent future leaks. Would ultimately like to source an o-ring but couldn't find one.

Anyway, feel free to reach out and I'll do my best to reply. I'm not on the forums that often so please PM me. Good luck!
 


OP
maestromaestro

maestromaestro

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Thread Starter #4
Here I am! Thanks to Erick_V for the mention and thanks to maestromaestro for reaching out. So upon listening to the sound file, reading your description and looking at the photos, I will say it sounds nearly exactly like the issue that I had. The culprit in the end was the input shaft bearing, which is located just on the other side of the cover you took a photo of. Doing my own diagnosis, I did the very same thing that you did. Had the car up on jack stands, ran it, put a little load on it with brakes & gas and used a stethoscope to pinpoint the noise. Same exact spot. It's very loud and crunchy when you use the stethoscope! SO - I would recommend starting there and having it replaced. (You can buy a kit with both input & output shaft bearings; PM me again for sourcing parts help if interested.) This will require pulling the trans, opening it and replacing two easy-to-reach bearings. When I did my rebuild, I replaced everything. The output/input shaft bearings are easy to get to and replace so it would be pretty straightforward to do in a weekend if you are comfortable with this sort of thing.

I don't know why it would sound the loudest at the fuel rail. Perhaps it's how it is connected to the block or maybe there's a bracket that touches the trans. You may have other issues, too. And, as an aside, all of the oily residue on your trans - I had that too. It's trans fluid leaking from the seal around the trans gearshift housing assembly. There's a small o-ring and a lot of surface area there. On mine, a good bit of corrosion had caused a leak. I used some very careful cleaning there with mild steel wool to dress it and put plenty of trans fluid & silicone paste there to prevent future leaks. Would ultimately like to source an o-ring but couldn't find one.

Anyway, feel free to reach out and I'll do my best to reply. I'm not on the forums that often so please PM me. Good luck!
You, sir, are a credit to humanity. I am not sure if I’d want to pull the tranny out by myself. Actually, I am quite sure I won’t - don’t have the skills and the right tools. In this the case, it may be cheaper to pay for a tranny swap, rather than a rebuild, I would think. Now, that Clarke one with an LSD looks tasty....
 


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#5
You, sir, are a credit to humanity. I am not sure if I’d want to pull the tranny out by myself. Actually, I am quite sure I won’t - don’t have the skills and the right tools. In this the case, it may be cheaper to pay for a tranny swap, rather than a rebuild, I would think. Now, that Clarke one with an LSD looks tasty....
It looks so tasty. I have already decided that if I do go forward in the future with a track build on this car, I'll swap one in. Some day... :)
 


OP
maestromaestro

maestromaestro

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Thread Starter #6
Upon considering the numbers (cost/ benefit), I am leaning towards sourcing a lightly used tranny and buying a LSD/ kit separately. It looks like I could get a transmission for about $750 shipped, plus $1000 for a Wavetrac. Throw in a new clutch ( perhaps ST200) and a DM flywheel, and I’m looking at about $2400 in parts. Install will run about $1100.

Clarke would run $4100 shipped alone, and I’d have to send them mine because they don’t have any FiST transmissions in stock. And, it is about 45 days without the car. It’d make more sense if I were running a big turbo. I’m not planning on blowing doors off p-cars, so - it makes me think that I’d be OK with a largely stock drivetrain.
 


Erick_V

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#7
Upon considering the numbers (cost/ benefit), I am leaning towards sourcing a lightly used tranny and buying a LSD/ kit separately. It looks like I could get a transmission for about $750 shipped, plus $1000 for a Wavetrac. Throw in a new clutch ( perhaps ST200) and a DM flywheel, and I’m looking at about $2400 in parts. Install will run about $1100.

Clarke would run $4100 shipped alone, and I’d have to send them mine because they don’t have any FiST transmissions in stock. And, it is about 45 days without the car. It’d make more sense if I were running a big turbo. I’m not planning on blowing doors off p-cars, so - it makes me think that I’d be OK with a largely stock drivetrain.
What other cars do we share transmissions with? I've considered picking up a spare motor (easy) but not sure where to find a trans
 


OP
maestromaestro

maestromaestro

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Thread Starter #8
I think ours is specific to the ST. There are 5 speed ones that go into an S or SE. Those *may fit*, but I can’t be certain. They are more easily sourced and are about 40% cheaper.
 




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