Here is his problem. Maybe an expert can help.

Sorry if this is in the wrong forum. Mods please move if it is not correct





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HELP..... Tranny Woes!!

I am hoping someone can shed some light on my Tranny situation in my 2nd gen RX7.

My manual trans is currently making a ticking noise. I use the analogy of it sounds like the baseball card taped to the front forks of your bicycle with the card running on the spokes (come on we've all done it).

I had better start the story at the beginning.

A couple of months ago I was running my usual autocross series (This is about all the car (90 RX7 N/A) is used for). When I had a horrible 2 - 1 downshift; It just crunched in real nasty. That is when this tranny (A rebuilt 86 model) started to make the "card in the spokes" noise.

I figured I bent something a bit but wasnt going to quit.

2 runs later on one of my massive launches (about 7000 out of the hole with 15 feet of wheel spin to keep from bogging) just starting to hook up real nice and the tranny GRENADED!

Toss a grenade under your car and see how it feels!



I have now rebuilt my original tranny (new bearings, synchros, shift forks). Did Imention I am very fussy and I also have a lot of industrial mechanic experience (in my defense).

It has worked great! I put on about 80miles around the country side and then to my closest event. I was staging and noticed a very faint ticking from below and went out on my first run and immediatly upon starting the ticking got extremely loud.

EXACTLY LIKE LAST TIME (FOR F*$% SAKES)

I didnt race any more but I did drive the car home 60miles without incident.



Let me try to explain the ticking better

When the clutch is engaged and the tranny in neutral all i hear is the usual gear whine (at any RPM or duration).

When I speed up or slow down (reverse included) the ticking changes frequency relatively.

In first gear the ticking is very loud.

In the other gears it is very faint. I cant usually hear it over my very loud exhaust untill I am decellerating.

Again I will say that the ticking doest not exist when in nuetral bu tranny rotating.

The noise is also very distinctly coming from in front of me (sitting in seat).

Fresh rebuild and I didnt even crash the gears (yet). Does anybody have any idea what may be wrong.

I know I have to take it apart.



Very, very, very frusterated!



Thanks.

hmm, was there any wierd damage to the parts you changed last rebuild?



mike

The gears themselves may be damaged. First gear sounds likely.



At the factory we describe it as a "tac, tac" A high spot on one gear tooth. With a load on the gear it would be louder. A tooth slightly bent might do it, too. Broke in first gear both times right? If a gear tooth is bent and very heavily loaded it would force the 2 shafts apart when coming into contact.



Just a theory from doing warranty inspection on industrial gears. Hard to determine without seeing it.



Are you talking about Greg or Derek?

yeah but he put it back together and it was fine?!?



mike

It's only a theory, but:



If a tooth is slightly bent it's really hard to tell. Automotive gears don't have that close of a fit tolerance. If the bent tooth was also not in contact while he put it back together it would still go together easy.



Driving around only lightly loaded in first before changing gears would keep all the load off the bent tooth allowing play between the gears to take up the slack. It would make the tap tap tap sound because one spot is not contacting as cleanly as the rest.



Heavily loaded on hard launch first gear is jammed hard together. The misshapen gear tooth would be like jamming a 3mm steel ball through a 1mm space. It would force the two gears and shafts apart pretty abruptly.



You should see what happens to a gear when the key between the shaft and gear tries to turn in the keyway! The gear usually breaks into 3-4 pieces.

Derek B.

yeah, you could be right. in fact you prolly are, its just odd that it worked after the rebuild



mike

I actually have never removed first gear from the shaft on eithr of my rebuilds. only done synchros and shifting stuff.

The tranny that grenaded has not been dissassembled any further than to remove the main shift rod out of the tail housing. Lots of gear chunks etc fell out of the oil passages. I didnt bother to tip it up to see if more was ther.

I find the bent tooth theory very plausable and it does make sense.

That will be a very expensive problem to fix considering the design of the secondary shaft

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Well this was certainly a shock. I had to look at your profile pics to place the face, Tyson, hahaha. Yeah it's Derek, not me. I'm silky smooth on my 306K tranny. https://www.nopistons.com/forums/pub...1047683473.gif

Had this happen on a VW, it was a very slightly bent shaft. Also had a clattering type noise when a shift fork got tweaked but that was pretty constant no matter what