Interesting topic. The new Brazi bays use a 1303 gearbox apparently but obviously mates to the Polo engine. If only you can have an overdrive setup of some sort hence only use it when needed via a switch activator?
if you have a five speed box with a taller gearing. Can you compensate for the slower fan RPM by altering the fan pulley?
Contact Pete Englos at the Cog box, tell him how many galloping horse's you have, how fast you want to go, and he will build you a bomb proof box to suit your needs. really nice guy too.
My t25 has five speeds in my opinion it maybe easier to swap it all ,engine box radiator...watch out for the dogleg ,burnt a clutch out trying to get one up a hill in 2nd or was it 3rd..
The 5 speed t25 box isn't the strongest of boxes. They like to eat 5th gear (mine has anyway). The 5th ratio is the same as top in a 4 speed box aswell. A load of hassle for not much gain. A 091 6 rib bay box has the same top gear ratio as a 5 speed box from a t25 unless you can get one of the much sought after boxes from a 2.1wbx.
dont know what the costs would be but i think some people have fit a subaru 5 speed box with reverse-cut ring & pinion cant see it being cheap http://www.subarugears.com/
I've asked this before. If you search you should fine the thread. If I remember correctly there is two options, one is changing the gear ratios which is hideously expensive and I can't remember the other but equally expensive.
Going off what everyone is saying here you are just better off spending the money on sound insulation and reducing weight of the van. I do long commute weekly in mine and all I did was buy good speakers and turn the stereo up, plus build low weight furniture
It's going to go in my Crewcab not my Westy. Not a lot of scope for chucking things out. The idea is to keep the revs low at high cruising speed, I'm thinking a 4th gear cog swap on a six rib 091 is the way to go?
Or just fit huge back tyres. That would screw up the rest of the ratios aswell though i suppose. I wonder if any of the 4th or 5th gear ratios from a t25 box will fit a 091 6 rib bay box.
Geneberg has a good page about 5 Speed boxes: http://www.geneberg.com/cat.php?cPath=13_387 You could get your 4 speed reconditioned and put in a type 4 final drive instead. Thats about £700 though.
This might not be for you at all, but have a look at this http://www.brick-yard.co.uk/forum/t3-18t-conversion-build-thread_topic76783.html great power, 5 speed box suited to the engine but not that straight forward to fit. It would make your crew cab a lot of fun
