02 gt grinding sound

Discussion in 'Other Hobbies' started by 07gts197, Nov 18, 2019.

  1. 07gts197

    07gts197 forum member

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    I know there is another section for all s197’s but I cant find it on tapatalk. Anyway my 02 gt has been sitting for a few months because work has been so busy. I just got it back up and running but theres one issue. Theres a grinding sound like a circular saw cutting a 2x4 when in 3rd and 5th only. Easing off the gas seems to pretty much eliminate it. It sounds like its coming from the flywheel/clutch area. Any ideas what it might be?




    By the way it has a tr3650.


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  2. SPeace-ATL

    SPeace-ATL forum member

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    That sounds a lot like the sound the rear cluster bearing makes when it is getting loosened up.
    The dynamics of pressure on that bearing are different for different gears and with/without load.

    I don't know what sound the front cluster bearing makes when this happens, but on a TR3650 the nylon fork pad inserts tend to crumble and the plastic debris always seems to get trapped in the front cluster bearing cage. I can't see why that would affect only a couple of gears, but again, the dynamics of the cluster shaft do change with the different gears - particularly if the bearings have loosened up.

    My suggestion is to replace the bearings and shim it up properly.
    May as well replace the synchro rings too while it is apart.

    Stan
     
    Last edited: Nov 20, 2019
  3. 07gts197

    07gts197 forum member

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    Before I get too deep Im going to dump the fluid but if that doesnt work I might just upgrade. It wasnt making a peep until after it sat.


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  4. 07gts197

    07gts197 forum member

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    Yesterday I dumped the old fluid and refilled it with dex/merc, no difference. I though if it was internal it would be affected by new fluid but no it seems there is no change at all. Id hate to buy a new trans and find out this one isnt broken. Any other suggestions? Its odd how its only affected by certain conditions. Like if Im in 5th and press the clutch in it wont do it, like only when there is no load. It just seems odd to me as 5th gear and the input shaft is still spinning.


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  5. SPeace-ATL

    SPeace-ATL forum member

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    I still think it is the rear cluster shaft bearing. Listening to the video, it seemed fine in all the other gears. I've heard that sound once before and that was the issue. The noise would come and go. It mostly did it in fifth gear and it had to be traveling "at speed" before it would do it. That one bearing is a "slip-fit" on the cluster shaft and is not pressed on. If those rollers aren't turning freely the center part of the bearing will spin (metal to metal) on the cluster shaft and make strange noises.

    Stan
     
  6. 07gts197

    07gts197 forum member

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    Not that I don’t believe you I’m just not sure. I’m assuming you’re referring to the output shaft bearing, and from what I’ve read is that it would keep making noise as long as the driveshaft is turning. It doesn’t make sense that it only happens in 5th.


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  7. SPeace-ATL

    SPeace-ATL forum member

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    That is true about the output shaft bearing and that one rarely goes bad because it is so large and heavy-duty, BUT, NO, I am talking about the rear CLUSTER SHAFT bearing. Now, if that cluster bearing went completely bad it would make noise anytime the input shaft is turning, (input shaft gear turns the cluster shaft all the time) BUT for the TR3650 there is a curve-ball setup for that one bearing in that is does not press onto the cluster shaft (AKA Counter Shaft). It is a slip fit and under some conditions, especially when the bearing is stiff, or the shimming is loose, it will spin on the shaft rather than roll on the needle bearing rollers. This is pretty rare.

    I am not making this up. I am into these transmissions on my workbench almost every day. I built a transmission that immediately had that same noise in fifth gear on the highway. There were no other complaints. I found the rear cluster bearing was spinning on the cluster shaft. I replaced that one bearing and re-shimmed the bearing and it was fine.

    The dynamics of the cluster shaft change when fifth gear is pulling because the fifth gear is beyond the rear cluster bearing. All the other gears that use the cluster shaft are between the front bearing and the rear bearing. Lateral stress on the fifth gear makes the shaft tend to pivot on that rear bearing and if the shimming is loose then it can move. The T-45, TKO, and the T-56 family of transmissions have a third bearing on the rear tip of cluster shaft that can prevent the shaft from wallowing in the bore in fifth gear, but not the T-5 nor the TR3650.

    Stan
     
  8. 07gts197

    07gts197 forum member

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    I wasn’t insinuating that you didn’t know what you were talking about, I’m just not convinced but if you think thats what it is you’d know better than I would. Do you think this bearing can go bad after sitting for a month or so?


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  9. SPeace-ATL

    SPeace-ATL forum member

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    Almost anything can happen... When I think "I've seen it all" something new surfaces! If there is some debris in the bearing so that it doesn't want to spin freely it would be easier to spin on the shaft than to "roll".

    I'm not offended. I just know that there are lots of people on forums that don't have the experience and are tossing out advice that is flawed. I needed you to know I have lots of experience with these transmissions. It isn't proper to actually plug my business on a forum since I am not a sponsor here but I want to share my knowledge and help people with transmission issues as best I can.
     
  10. 07gts197

    07gts197 forum member

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    Well I appreciate the help.

    So I took it out for a short spin to see if anything else popped up and I got a few interesting tidbits. The noise is also happening to a degree in 2nd and 3rd but only during engine braking in 4th. Also its affected by suspension (ie. bumps in the road) and I noticed my clutch engages really close to the floor. While in reverse if I don’t give it any gas with my clutch maybe an inch off the floor it’ll stall. I’m thinking there is more than one issue going on now.


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  11. SPeace-ATL

    SPeace-ATL forum member

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    Hmm, something seems to be going on in the clutch area if the pedal engages so close to the floor. It could be a stretched cable, or the quadrant adjustor could have slipped. The adjustment for the cable is to pull up on the pedal. You did say this is a 2002? A bad throwout bearing can make similar sounds, but that only varies with pedal pressure and RPM. The TOB won't care which gear you are in. I know that noises deep in the transmission often sound like they are in the bell housing and sometimes differential noises sound like they are in the transmission!

    I tend to agree that these two issues are probably not directly related.
    The rear cluster bearing CAN make noises in any gear. Even in neutral with the clutch pedal up, but from experience, I've seen it be really noisy in fifth gear at highway speeds. Again, I attribute that to the dynamics of the fifth gear being to the rear of that bearing and putting a different stress on the bearing.

    Stan