Did my first rebuild on a CTR S80 tranny i have had for years that i took out after getting the normal 3rd gear grind. I took it out early so there was minimal to no damage other than the normal wear to be expected.

I bought the synchrotech carbon master rebuilt kit along with the 3-4 gear hub so that i could replace everything that might have some wear/damage from 3rd grinds. Went through it and replace all the synchros, bearings (except diff bearings), sleeves, and the 3-4 hub. All went smoothly and the tranny went back together easily. Got it in the car and filled with honda MTF. Cranked up the car and let it run at idle for 10 minutes to get the oil all over everything and proceeded to shift 1-5 and R while up on stands with no wheels on. Shifts great, goes in all gear without issue (1st is a little "tight", but not enough to cause concern).

I went and took it for a spin last night to it drives great. The issue i am worried about is a whirl noise in the higher gears, 3-5th that only happens under acceleration or a little less under decel. Its not a grind or a scary noise, its just something of concern since all the gears and diff are the same and it has fresh bearings.

As a note, i also did a new clutch (CC stage 4, resurfaced flywheel, and new pilot/throw out bearing), and also pressed in ARP wheel studs while i had the arms off the car. The wheel bearings are new koyo's with maybe 2k miles on them. When i pressed the hubs out of the wheel bearings the race stayed stuck on the hub which is normal, and when i pressed it back in, the bearings were tight as if the race wasn't sitting correctly so i used some old spacers to hold the inner race of the wheel bearing while pressing the hub in so it sat in correctly. After doing this they felt nice and smooth again. Clutch also had some first gear chatter that deceased as i wore it in on the test run.

Any thoughts on what might be off? The only thing i remember being different was the counter shaft nut went on past where it had previously been staked. it is possible i put this on to tight? i used an electric impact to get it tight since i was holding it in my lap, but i didn't pound it on excessively i thought.

 

As an update, i took the car out again this past weekend and it drives and shifts perfect. Its just the noise, which sounds similar to dragging brake rotor that has a little surface rust if you have heard that noise before. i even started to think it could be coming from the front suspension/hubs, but it is so easy to isolate to 3/4/5 under load.

I am going to take it out and put the gsr tranny i had in before. ill confirm if was the tranny and then pull it apart and take a look a 3/4/5. Has anyone put in a washer or something in a wrong orientation that has caused any issues? I know about the input shaft wash and its concave direction and made sure that was correct when reassembling. i just don't know if there is something on the shafts that may be pushing 3/4/5 just off of each other enough to cause the noise.

 

Replace the wheel bearings.

 

I just did new koyos just a couple hundred miles ago. I'll admit that was a concern since I did just press in new studs and had to press the splindles out of the hub. But I will know for sure when I swap the tranny back to my old perfectly fine unit. If there is still noise I will know to look elsewhere.

 

So as an update I did pop my old gsr tranny back in and there is no noise anymore. It is certainly the tranny.

I got a manual with the specs for the clearances so I am going to open it back up and inspect/measure for what maybe the issue.

 

the noise is most likely coming from the diff, specifically due to either; wear on the diff bearings, incorrect preload on the diff bearings, or both. replace the diff bearings and make sure to measure and adjust pre-load properly with the correct size shims. Even with brand new bearings, if the pre-load is not correct, it will cause noise and premature wear.
If it's not the diff, it could possibly be the pre-load on the main shaft. That needs to be measured and shimmed correctly as well.
diff pre-load is measured with a dial type torque wrench that measures inch/lbs, and requires a custom "socket" to be made so you can spin the diff with the torque wrench.
Mainshaft pre-load is measured by measuring various thicknesses, distances, and tolerances.

 

Thank you. I haven't cracked it open yet, but the diff/bearings/shim was all oem. Other than removing it to clean up, I put it all right back in. I'm glad I pulled it though as I do think one of those items are not where they need to be.