gearbox ratios

[fergus]

Am considering a more robust gearbox than the caterham 6spd unit. Although BGH designed the box, they don't have anything further to do with them in terms of rebuilds, etc.

If I move to one of their E8 specification 5 spd boxes, the ratios are significantly more widely spaced. I have a 220hp k, and was curious if others had mad the move from 6sp to 5sp.

Putting the 5 and 6 spd ratios into the gear chart calculator on Hewland's site shows the massive drop in revs when using the 5 spd box (this is when using 13" wheels and a 3.92 final drive).

Any experiences welcome.

I've had my box rebuilt 4 times by various people and am considering a move to an alternative....

[Dave J]

what has failed on your 6 box previously ?

Have you made all the upgrades to the 6 speeder ? that have been released over the years ?

Phil stewart at road and race has a lot of experience of the 6 speeder and can aplly the upgrades for you.

With a modest 220bhp and probably around 160 ft/lb torque the 6 speeder should be able to cope. Unless you are quite hard on boxes anyway, in which case you may be better off with something like the 5 speed quaife probox ?

[fergus]

Dave J said:

what has failed on your 6 box previously ?

Have you made all the upgrades to the 6 speeder ? that have been released over the years ?

Phil stewart at road and race has a lot of experience of the 6 speeder and can aplly the upgrades for you.

With a modest 220bhp and probably around 160 ft/lb torque the 6 speeder should be able to cope. Unless you are quite hard on boxes anyway, in which case you may be better off with something like the 5 speed quaife probox ?

selector forks, synchros, the cheap R&R baulk rings, which weren't lapped in very well.....

I've had a new 2nd gear with the oiling mods. Modded selector forks. A new indent selector. What else has been changed/upgrades?

I always get everything fully up to temp prior to gunning things (I ran an oil temp sensor in the gearbox for a while!). It's now whining on the overrun (and no, it isn't the diff), and 4th to 3rd, even with a good blip is getting recalcitrant. The 'bomb proof' E8 5 speeder looks good, but the ratios appear quite a lot wider than the very tight caterham 6sp ones. I've not heard good things about the baulk rings that quaife use. Apparantly, even with a lot of lapping in, they can sieze fairly quickly.....

[Red Seven]

"selector forks, synchros, the cheap R&R baulk rings,"

Is this for a road or track car?

If its a track car, then maybe you should be thinking about a dog box?

Edited by Red Seven on Monday 21st September 17:02

[sam919]

What about a 5 speed type 9 with quaiffe internals running in anti shock racing box/diff oil. Should easily be good for 250bhp and plenty of torque.

[fergus]

Red Seven said:

Is this for a road or track car?
If its a track car, then maybe you should be thinking about a dog box?

About 10% road, 90% track. I've raced cars with seq. dog boxes before, so noise isn't an issue. Any recommendations?

My current box is a 'dog of a box'

[fergus]

sam919 said:

What about a 5 speed type 9 with quaiffe internals running in anti shock racing box/diff oil. Should easily be good for 250bhp and plenty of torque.

Sam, can you PM me with more details plse. Unless I have a high 1st, I'm a bit concerened about having massive rpm drops between ratios with only 5 cogs to choose between....