87 rx7 with a swapped s5 drivetrain. been having this problem for a while now. in 4th and 5th gear at around 2-4k when you hit the throttle I get this weird metal noise. I did a pull with a friend and it did it in 3rd when I was at WOT but only for an instant. its inconsistent, like there's not rhythm to it, it does it more than it doesn't but sometimes it doesn't make the sound. I had 2 people take a ride and both of them said it was coming form the tranny tunnel, though there is no insulation there so it might be louder there because of that. Here is the video so you can get an idea of what it sounds like, any help will be appreciated:

 

Likley something on the exhaust is rattling against the chassis. There are a lot of rubber hangers down there, and if any of them are removed and the hangers bent in different ways, it will rattle not in time with anything

 

well the only thing I can think of that would be doing that is a piece of heat shielding by the exhaust, which I had to take a bolt out of to get enough clearance to slide the downpipe on. its the one right by the turbo on the firewall. ill slide under the car and take it off if I can do it without removing the downpipe to see if it makes any difference. Any other suggestions?

 

Just removed that heat shielding I taked about. still doing it. have no idea what is causing this and I have no way to diagnose it other than driving it but everything echo's. does ANYONE have any ideas?????

 

Do you have problems shifting into 5th or reverse? Could be a self-disassembling synchro

 

I would just put it up on jackstands, put it in gear then get you or your buddy to look and listen as it runs.

Remove the driveshaft and run just the transmission and see if it still happens

 

No, no problems shifting into 4th or 5th at all. in fact they are the smoothest gears to change into.

already did that, found nothing. I work at a dealership and one of the other techs are going to pull out the big guns and set up microphones inside the engine bay so we can hear what's going on because I have no doubt that sound is echoing from somewhere I just dont know where.

 

It is clearly coming from in the transmission tunnel though? I am looking to add some felt on my ashtray latch because of its rattle, is just the video is moving around too much to place sound direction, is just the passenger pointed directly at it at 7 seconds in

 

There is also a potential that the detents that hold your shift forks in place are allowing them to slop around under acceleration or deceleration. Have you checked out the transmission for glitter or to see if there is slop in the shifting?

 

another tech told me this a while back, wassnt sure if that was it because the engine bay echos so much and there is no foam insulation by the gear shifter anymore.

 

there is no insulation there anymore. if you take the shifter boot off your staring right at the pavement. it could be the tranny but it could also be echoing from somewhere else.

 

Update, drained the tranny and the fluid had glitter and some small chunks stuck to the magnet. going to pull it apart next week and see what exactly broke.

 

What color was the glitter?

Also, after my experience taking these apart, there are a couple tools you are going to want to use. Learned from experience.
1. Get a good set of snap ring pliers. Nothing with replaceable jaws. Those will just bend, you will get angry, possibly lose an eye when they break. Get a good set of pliers, it will save your time, your hands, and your sanity.
2. For the bearing puller, use a puller like the one shown in the FSM that has the ability to squeeze perpendicular to the shaft axis. If you use a standard puller, you will bend or damage the shims and retaining rings for the bearings. The jaws on the standard pullers spread when you put pressure on them if you try to use them on these bearings. You need the extra constraint to keep the jaws in place on the bearings because the transmission case doesn't allow for a good hold. If you have to make a set of jaws to do this, it WILL be worth your effort. I took apart one of these before I knew better, and because the transmission case is made of aluminum, trying to manhandle the bearings out wallowed out the holes in the case. Other than that, it is fairly easy to work on. The bearings and synchros could be replaced while you're in there, but are probably otherwise fine.

If you have questions, let us know. Good luck!

 

Thanks for the tips. I had a friend of mine who is a tech inside the shop take a look at the pieces and he said they looked like brass, so possibly pieces off the syncro's. Ill learn more when I get deeper into it.
trying to find a rebuild kit for this because he also recommended getting new snap rings because the ones we've come across have been so hard to get out we've ended up bending them, also bent the roll pin in the shifter housing because I was being stupid but that shouldn't be too hard to replace. i found a rebuild kit on rock auto but it doesn't say it includes the snap rings or roll pins.
also because this was swapped into my car Im not sure if this is an s4 or an s5 transmission. I initially thought it was an s5 but I have nothing that proves that. what makes it worse is I cant find any ID number and the car the tranny came out of was also a swap. any suggestions?

 

You will be able to tell which transmission you have after you open it up. The S5 transmission has a dynamic damper, which is massive drum type weight, bolted on to the rear of the main shaft. The S4 transmission does not have have a dynamic damper. The nut holding this on the S5 is about 40 or 42 mm but a 1-5/8" socket will fit. It's a big PITA to remove so just hope that you've got an S4 transmission.

 

Take it easy when you're taking this thing apart. It gets easy to chip a gear tooth.

Also, when you get to removing gear stacks from the upper shaft, take the whole stack off for each gear and put a ziptie through the stack. That way all the needle bearings and stuff stay with their appropriate gear.

 

Good idea. Im about to get to that point now.
Also, I found this in the tail shaft.! you think this could be causing the noise? when I pulled off the tail end of the tranny for the first time there was a ton of bronze pieces that seemed to come from this. also im taking my driveshaft to a shop to get fixed because that has a kink in one of the U-joints

 

Reminds me of a similar noise I had in my S5-T. Extremely rare but only at WOT around 5-6k or so, was like a ball bearing rolling down a metal washboard. Nothing was interfering with the fan, apex seals are all fine, stripped the tranny down and not a glint of metal or chipped teeth, no slop in any bearings. Never found out what it was, haven't had it happen in years.

 

You could replace that rear bushing while you're there. However, until you inspect the synchros, you can't be sure that is the source of your problem. It still looks in operable shape, just not so pretty. It would just be a scraping whenever the rear wheels were in motion. If you were in neutral at a stop, it wouldn't do anything.