4 replies to this topic

[John Clayton]

Option 1: Get another 2H box off eBay or similar (how much do they go for?
Option 2: Replace the 2nd gear sprocket in this box (if that is possible?)
Option 3: Get a straight cut box if it's likely that the standard ones won't be man enough

The Car is an 87 model and has 100 Bhp.

Full Spec is listed on the car’s blog:
http://www.theminifo...howtopic=129848

[bmcecosse]

If it's not jumping out of gear -just keep using it. 2nd gear syncros doesn't last long anyway unless you are willing to double-de-clutch it - and you will have to now!And start saving/looking for a straight cut box......

[John Clayton]

OK. Each time I crunch into 2nd (at high revs on a rally stage it's difficult to avoid a crunch, even when double-declutching it) but I'm slightly worried that each crunch means more metal filings going round in the oil?

How much work/cost is involved in replacing the 2nd gear synchro?

[John Clayton]

P.S.

Just seen the following which is interesting reading:
http://www.kad-uk.com/engine.htm

"At the lower stage of tune it is possible to use A+ cranks and rods, helical drop gears and a standard 4 speed A+ box with a Twin cross pin diff. Whilst this will give reliable service upto 120 bhp, above this it is asking rather a lot from components designed for sixty-odd horsepower.

The standard helical 4 speed can be used but is really only suitable for stage one conversions up to 120bhp. Even at this level the standard diff is an immediate weak link and should be the priority for change since the standard cross pins are very weak. The twin cross pin types on the market are a good fix on a budget as limited slip types require drive shaft and inner CV changes to remain reliable.

Stage two and above must use uprated transmission components throughout with dog engagement gearboxes required for stage three and four. As with the gearboxes, clutches and flywheels also need to be addressed in the same fashion."

Edited by John Clayton, 14 April 2011 - 04:26 PM.

[Cooperman]

For rallying where you will have a more 'cammy' engine and, presumably, a low FD ratio, you do need a close ratio box to keep it 'on the cam', so the best bet is to get a SC Cr gear set and build it into your gearbox casing with new cones, hobs and bearings. The transmission is always the weak point on rally cars and a cross-pin diff is virtually essential unless you are going to run an LSD. That's a personal choice really but some, me included, can't get on with the LSD on loose surfaces. On my historic car which has a 286 cam I run a SCCR box with a 3.9:1 FD ratio. I do have SC drops, but i did 30 rallies with helical drops and now I wish I had not changed as they are simply so damn noisy.
I've broken 2-planet wheel diff pins, so I now run a cross-pin, although I did once snap one of the pins in a cross-pin.