reverse gear rattle ??

[Exodus]

got a issue somewhere in y drivetrain,, when in reverse and peddle depressed (not fully ) o hear a gear rattle,this is the only condition this happens in
fully or not at all nothing happens

left my 08 5 speed at the mec's for 4 months while at work so there was no pressure to fix it
he went through the entire trans and found nothing at of wack
transfer has been apart to replace the shift fork and nothing found there either

me and the mec really need some insight on this

 

[Jeepwalker]

So, let me see if I understand you correctly: Your H3 has a 5-spd and you hear a noise (rattle) in reverse under certain conditions?

 

[Jeepwalker]

How loud is the noise? Reverse often makes noises because the reverse gear is straight-cut. Where the other gears are helical cut (angled) and quieter. Reverse is almost an after-thought. See picture below ...lower rt. I would normally look at the gear teeth and/or the thrust washer on the drive gear (which drives the reverse). There's a synchronizer and the gear itself. But if your mechanic didn't find anything ...I don't know what to say. You might also check your engine mount since these do fail on the H3's and in reverse a band engine mount could be allowing the engine to lift. Put the engine in reverse, foot on the brake, and look under the hood and give it some 'gas' and watch the engine to see if it lifts up.

 

[Exodus]

How loud is the noise? Reverse often makes noises because the reverse gear is straight-cut. Where the other gears are helical cut (angled) and quieter. Reverse is almost an after-thought. See picture below ...lower rt. I would normally look at the gear teeth and/or the thrust washer on the drive gear (which drives the reverse). There's a synchronizer and the gear itself. But if your mechanic didn't find anything ...I don't know what to say. You might also check your engine mount since these do fail on the H3's and in reverse a band engine mount could be allowing the engine to lift. Put the engine in reverse, foot on the brake, and look under the hood and give it some 'gas' and watch the engine to see if it lifts up.

he put it up on the rack and stethoscoped it also ,so mount is irrelevant i'd think
guess it might just be something i gotta deal with

 

[Jeepwalker]

.....he went through the entire trans and found nothing at of whack

Did your mechanic disassemble the transmission? Or just inspect the trans on the hoist? You don't get the same noises when it's not under load, in the air. The only way to know what's going on for sure, is to remove & completely take apart the transmission. Then inspect all the gears/synchros/beasrings/parts associated with reverse. That would be the 'green gear' & parts, in the picture above, plus the straight-cut gear to the lower right. Could be a damaged gear or a metal shaving pressed on a gear which is causing your tranny's noise. Hard to say w/o listening to it. Manual transmissions are really easy to work on, for a guy with experience. Pretty straight forward. If the noise isn't too bad just wait and see if it gets worse.

Change the fluid using OEM fluid if you haven't already. Use the right GM or asian fluid. Or you might try a slightly thicker fluid ..but know that using a fluid different than OEM may make your shifting feel different (because friction coefficient at the synchro's will be different).

 

[Jeepwalker]

So ok. I re-read your description. Are you're saying with the clutch depressed (trans in reverse), vehicle not moving, ...that's when you hear the rattling noise? But you don't hear the noise when the clutch is out and driving?

If so, that usually points to a failing/worn pilot bearing, or bushing (whichever your H3 uses). That's the bearing/bushing which fits into the rear of the crankshaft (example picture below). It's purpose is to support the tip of the transmission input shaft (# 100 in the diagram ..in the link below, group 3). Most people think the main transmission shaft inside is one long shaft. It isn't. The transmission input shaft which sticks out of the transmission isn't very long, maybe 8-9" (~21cm) or so. It needs that pilot bearing in the crankshaft for support. The pilot bearing is non-greasable. They can become dry and rusty over the years, and also be damaged when installing a new clutch (even if a new bearing was installed). When that bearing or bushing wears or is damaged (..or the wrong size installed new), the end of the input shaft can wobble and make a knocking noise against a bad/worn bearing or bushing. That's what produces the noise. It usually occurs at idle. Once you put load on the transmission (let out the clutch), the clutch sort of centers the input shaft and the load on the gears straighten the input shaft up and it doesn't knock against the bearing.

Those are kind of 'classic' pilot bearing noises. Does that make sense? I had a car which did that for years ...till I figured it out. You cannot see or service that bearing unless the transmission is removed which makes it difficult to diagnose. If that's the issue, you should change it so it doesn't cause downstream damage to the transmission input shaft or associated gears. Don't use a cheap bearing. Hope it helps.

Below is the transmission breakdown if you need it:

Getting a Grip on the Aisin AR5 Transmission - Transmission Digest

The sports or performance cars are still produced with manual transmissions, as are many imports, but the decline is here to stay for the foreseeable future.

www.transmissiondigest.com

This is a general picture from google (as an example) of a pilot bearing.

 

[Exodus]

I have no idea why you would he just "looked" at it on the rack ?? he has had it apart twice now, first time there was a chewed up gear, this time he only found a couple pieces of metal that are from some sort of clip

 

[Exodus]

Did your mechanic disassemble the transmission? Or just inspect the trans on the hoist? You don't get the same noises when it's not under load, in the air. The only way to know what's going on for sure, is to remove & completely take apart the transmission. Then inspect all the gears/synchros/beasrings/parts associated with reverse. That would be the 'green gear' & parts, in the picture above, plus the straight-cut gear to the lower right. Could be a damaged gear or a metal shaving pressed on a gear which is causing your tranny's noise. Hard to say w/o listening to it. Manual transmissions are really easy to work on, for a guy with experience. Pretty straight forward. If the noise isn't too bad just wait and see if it gets worse.

Change the fluid using OEM fluid if you haven't already. Use the right GM or asian fluid. Or you might try a slightly thicker fluid ..but know that using a fluid different than OEM may make your shifting feel different (because friction coefficient at the synchro's will be different).

I have no idea why you would he just "looked" at it on the rack ?? he has had it apart twice now,
it made the same noise when it was on the rack also
first time there was a chewed up gear, this time he only found a couple pieces of metal that are from some sort of clip

 

[Exodus]

So ok. I re-read your description. Are you're saying with the clutch depressed (trans in reverse), vehicle not moving, ...that's when you hear the rattling noise? But you don't hear the noise when the clutch is out and driving?

If so, that usually points to a failing/worn pilot bearing, or bushing (whichever your H3 uses). That's the bearing/bushing which fits into the rear of the crankshaft (example picture below). It's purpose is to support the tip of the transmission input shaft (# 100 in the diagram ..in the link below, group 3). Most people think the main transmission shaft inside is one long shaft. It isn't. The transmission input shaft which sticks out of the transmission isn't very long, maybe 8-9" (~21cm) or so. It needs that pilot bearing in the crankshaft for support. The pilot bearing is non-greasable. They can become dry and rusty over the years, and also be damaged when installing a new clutch (even if a new bearing was installed). When that bearing or bushing wears or is damaged (..or the wrong size installed new), the end of the input shaft can wobble and make a knocking noise against a bad/worn bearing or bushing. That's what produces the noise. It usually occurs at idle. Once you put load on the transmission (let out the clutch), the clutch sort of centers the input shaft and the load on the gears straighten the input shaft up and it doesn't knock against the bearing.

Those are kind of 'classic' pilot bearing noises. Does that make sense? I had a car which did that for years ...till I figured it out. You cannot see or service that bearing unless the transmission is removed which makes it difficult to diagnose. If that's the issue, you should change it so it doesn't cause downstream damage to the transmission input shaft or associated gears. Don't use a cheap bearing. Hope it helps.

Below is the transmission breakdown if you need it:

Getting a Grip on the Aisin AR5 Transmission - Transmission Digest

The sports or performance cars are still produced with manual transmissions, as are many imports, but the decline is here to stay for the foreseeable future.

www.transmissiondigest.com

This is a general picture from google (as an example) of a pilot bearing.

it only makes that noise while in reverse and peddle pressed down,(not to the floor) and moving

 

[Jeepwalker]

Does the sound increase/decrease if you give it a little speed? Does the noise follow engine speed? (possible throw-out bearing issue??). When the clutch is depressed, the input shaft can wiggle if the pilot bearing is worn/loose. Let the clutch out and the clutch helps 'center' the input shaft, sound goes away.

That's all I can think of w/o being there or hearing it in person. Sorry. It's probably going to require a deeper inspection or digging in to find it.

Maybe someone else has other ideas...

 

[Jeepwalker]

Manual transmissions are not that difficult. If he's had it apart 2x ...maybe it IS the pilot bearing/bushing (which isn't inside the transmission). Maybe he's overlooking it (cheap/worn/damaged/wrong size, etc) ...or a clutch component.

Hopefully your guy will figure it out. Best of luck.

 

[650Hawk]

first time there was a chewed up gear, this time he only found a couple pieces of metal that are from some sort of clip

I think I'd be looking for wherever the pieces of metal came from. They don't just appear out of nowhere.