Rebuild a gearbox or get another one

[93_Clubman]

Few years ago a couple of forumites mentioned getting their 5 speed GBs rebuilt for $2k-$2.5k.
Given no improvement from Redline oil change, it might be worth trying another GB oil.

[madjak]

Try Amsoil MTG... still the best oil I've used.

My 4th and 5th are crunching if I shift quickly which indicates the synchros are worn. I am thinking of pulling down the box and replacing them. I expect it to be a large undertaking though as the 6 speed needs lots of special tools to pull apart. The cost for the synchros isnt a lot... however if you add bearings and shift forks in and you're up over the $400 mark just in parts. I am yet to decide if I'll simply change the worn parts and seals etc, or go for a larger rebuild.

I'll document it all when I do it.

[Magpie]

Madjak can you go straight cut gears as well when you rebuild

[zossy1]

Dog gear set from Pfitzner =$5K or so from memory... Is no longer on their price list.

[madjak]

Par do a cheeper set. Could just replace 3rd 4th 5th and 6th. Still $3-4k though.

May as well just save up for a quaife Sequential!

[orx626]

http://www.ebay.com.au/itm/Mazda-MX5-NA-NB-NB8B-BP-1-8L-6-Speed-Gearbox-Transmission-Good-Condition-Used-/272201790812

$990 incl. GST everyday of the week...whilst stocks last.

[Purfler]

It depends on how interested you might be in getting your hands dirty, or what facilities and tools you currently have, but you could consider a DIY gearbox swap. For my NA I bought an engine crane and took the engine and gearbox out together - not that much of a pain, just time consuming. The crane cost about $350 and I needed one anyway for the rebuild of my Datsun 2000 Sports (as I said to SWMBO ) I replaced the gearbox with a low KM jap import (cost all of $230), did the clutch, all seals, timing belt, pump etc. Very easy with everything out of the car. I now want to rebuild the original gearbox as a learning experience, and a good excuse to buy a press. (that's going to be an interesting conversation at home)

Of course the whole idea might seem absurd to you - you might much prefer just driving the thing!

Regards,

Tim

[dzammit85]

Just thought I'd give you an update on this, turns out it's not worth rebuilding, Most people on here are saying it's going to be more money to rebuild then get another one, I also called mx5 mania to see if they can get it rebuilt and they don't, they just replace it
like orx said, automotive plus $990 everyday of the week, I'm just better off buying one
I've got the clutch ready to go, I got the exedy sports tuff (non button).

Now I know this next question has been covered a lot, and there is so many different opinions on it, though I will ask it anyway

My nb8b will soon have a torsen 3.9 in it, thus making it rev a little more

Now here's the big question, that will open a can of worms.
Will a lightweight flywheel be worth it for this set up, or is a heavier flywheel better, the car is going to be used for track/everyday

Thanks for everyone's input also

[greenMachine]

Lightweight.

Ditch the 3.9 and get a 4.1. If you are going to the trouble of doing the swap, make it worthwhile.

[billybunter]

As to that plastic bush on the bottom of the gearstick mine looked alright at 55,000klm but didn't change too well. I picked up a new plastic bush from ebay for $20 and the end result was a much better shift.
Prior to that I had tried the delrin or whatever bush and although it shifted fine it was very high on the vibration factor. Holding on to the stick was like the vibes on my motorbike. So I removed it and went back to the original plastic factory bush and then did a 11.000 klm road trip north and the end result - very happy I did the change back.
It may or may not help you but for $20 to find out if it helps or not - i'd give it a go.

[Mr Morlock]

you are right about the worms.