Backstory:

Blew my 5-speed (1997 NA) while getting on it in 5th gear. Very noisy, sounded like driving on rumble strips.

Replaced 5-speed w/ a 6-speed from Planet Miata (thx guys!). Dan at Andrewtech used the info I got from this lovely site (thank you lovely people) and used the NB tranny plate, swapped the 2 connectors, used 5-speed speedo gear.

Yesterday, he drove it home to me and had a coolant line come undone, thus overheating. So, we finally got it back on, filled, drove it home (he did). This morning, I drive into work rather cautiously.

I noticed a few things:

1) I've got the polyurethane rear diff mount bushings from 949Racing (Energy Suspension). There was some NVH at higher speeds, but now its rediculous. Could my driveshaft be messed up too? The rear diff appears to work fine (according to Dan and my driving).

2) The tachometer seems to be messed up. It appears to work fine below 4k rpms, but right around 4k, it doesn't seem to move in response w/ the engine sound (revving). Is it possible we messed up something w/ the tach while hooking back up the wires to the 6-speed? Or something else?

3) I need Brain to retweak my tune. It's running like crap. That, and I need to go MS2 and COPS. Just need him to drop what he's doing and book me.

<3 foo

 

what about the front diff?

 

Sorry, coming from a Subaru world.

 

What flywheel and fluid are you using? I have an early 6 spd and it made tons of noise with 7lb fw and mobile 1 synthetic. Changing the fluid to redline made most of it go away.

 

Lightweight Flywheel, ACT I believe. I think it was the 10.5 lb one?

Gear oil was Lightweight Shockproof in the 5-speed. 6-speed has Motul 300 I think.

Now maybe the tranny's making the noise, but it seems to eminate from the driveshaft to diff/rear tire area.

I'm wondering if the diff mount bushings are causing this. I really do not like them at all and wish I replaced the worn stock bushings w/ OEM rubber.

 

UPDATE (Happy ending):

So, drove the car to Andrewtech. Tach was messed up above 4k, ran like crap above 50mph, really rough.

Get it on the lift, put it in 6th gear, get up to 70mph. Aha! Found the source of the vibrations. There's a rubber damper thingy on the diff where the drive shaft meets up. The rubber tore itself off it's inner liner/metal (attaches to the ring/pinion or whatever in the diff housing.

Anyhoo, removed the rubber, left the old part on, and it's fine!

Also, the tach was messed up b/c of all that as well, so now it's better.

 

Glad to hear it was as simple as that man...

 

yay...so no loose driveshaft bolts

 

Yep! What a relief! Hopefully someone else might find this and can use it to quickly troubleshoot.

Regarding the 6-speed, well, I kinda mentally wondered how the eff could Savington find reverse on the track while going over 100mph. Yeah....I found reverse (albeit for a split second and the clutch was half-depressed) while driving ~40-50mph. Wow, there doesn't seem to be some sort of lockout like other 6-speeds I've driven.

I was shifting 5th to 6th and found 4th. So I went to move it over to 6th, and whoa! Found reverse. Unamused.

 

Yep it took me about 1.5 weeks to get used to shifting into 6th gear. I still doubt myself when i go back and worth from the integra to the miata.

 

Haha! I just drove an STI and was apprehensive, then, nah, this is ok. Get back in my car...careful, careful...