Hi Guys, building up my Close Ratio Gearbox at the moment, all going together well and will post some pics soon. I've just noticed that there are three o ring style seals that seal the selector shafts as they pass through the gearbox case. As there is a big hole in the bell housing for the rods to pass through this is a bit of a leaking point. Does anyone know where i can get new ones from? I'm going to try a normal seal supply shop during the week but they appear to be a strange combination of a square and a round o'ring. Anyone else come across this problem?
Col
Suggest you have a chat to Bruno, Vin or Hugh as they are very experienced with these units
Barry
Hi Colin,
Later gearboxes have shorter shafts that don't protrude and the bellhousing is cast closed in that window area; problem solved by the factory......not much help for early boxes though. In any case, I'm looking at the same thing at the moment with 2 original GTA 'boxes I have up for rebuild, so I don't want to change the bellhousing etc.
Firstly, the O rings started life as just plain round section: wear and squeeze fit cause the wierd shape. Not hard to source at seal place.
Secondly, I'm thinking of making up a small cap with gasket and attached by 2 screws into the bellhousing to effectivly close over the ends, with a minimal hole for the reverse light switch shaft.
Quote from: vin sharp on May 21, 2011, 09:17:07 PM
Hi Colin,
Later gearboxes have shorter shafts that don't protrude and the bellhousing is cast closed in that window area; problem solved by the factory......not much help for early boxes though. In any case, I'm looking at the same thing at the moment with 2 original GTA 'boxes I have up for rebuild, so I don't want to change the bellhousing etc.
Firstly, the O rings started life as just plain round section: wear and squeeze fit cause the wierd shape. Not hard to source at seal place.
Secondly, I'm thinking of making up a small cap with gasket and attached by 2 screws into the bellhousing to effectivly close over the ends, with a minimal hole for the reverse light switch shaft.
That's a great idea. I've got to go through this on the box for my 66, Never thought to look there when I was chasing down the gearbox leak before I took it off the road...
Hi guys
Looks like the original O ring is an imperial one
Round
Code 113
Cross section 2.61mm
ID 13.76
OD 18.99
I also got some square section ones and am going to try them as the feel like they seal better, also looing into making a cap as Vin suggests but it is a complex shape to seal against.
Other leak points I have found
- the drilling hole for the interlock pins is sealed up with a 40 year old rubber plug, mine was has hard as a rock and completely useless so I've tapped a M10 thread into the hole and going to seal it with a grub screw and sealant
- The long through bolts just pull up on thick steel washers that pull up hard against the ali case. I'm currently turning up new steel washers with o rings on both sides to try and seal up this problem
- Not sure how much oil comes out the breathers but planning on running some tubes off the breather to a catch can
When Vin Checked out my gearbox build he commented that the machined sphere on the output shaft I had used was very worn. I had never really looked at this before but unfortunately I had to agree so I located a new one and rebuilt the main shaft. Since I'd gone to this much trouble I thought I'd better check out the bush that the sphere locates in in my drive shaft. Glad I did, it was really worn and wouldn't have provided much centre location at all.
After a bit of mucking around around getting the old bush out of the shaft (ended up welding a plate to it and bashing it out with large hammer) I machined up a new bush and pressed it in
Once I receive my flex disc from the us I'll need to get the whole assembly balanced, anyone know a good place to get this done?
I once read/heard that the Beninca workshop has a '3 plane' balancing machine - not sure if that helps.
Thanks Pancho
Here's a couple of photo's of the gearbox, just waiting for the front and rear seals to arrive, then i can finish putting it together
Shiny !
So Colin, is this an off the shelf CR gearset?
It's an off the shelf item
http://www.spruellmotorsport.com/alfa-gearset-close-ratio-gearset-free-syncros-p-2380.html (http://www.spruellmotorsport.com/alfa-gearset-close-ratio-gearset-free-syncros-p-2380.html)
It's a bit confusing as they stated it fits a 1750/2000 gearbox but it is for gearboxes with a circlip rather than a nut on the input shaft, and i think those gearboxes are from earlier cars.?, so i ended up getting 2 donor gearboxes to get all the bits i needed
Let us know how the car drives with this box in it, I am looking to go get one based on your fedback. What made you go with this gear set over others out there?