[Fot] T5 conversion

[J.C. Hassall]

Who makes a bell housing adaptor?  Does the crank have to modified for the
input shaft bushing?  I assume (uh oh) that clutch/PP can be adapted to the
wet sleeve crank?  My curiosity has been piqued.

Jim

Fat-thumbed from my iPhone

> On Dec 22, 2014, at 7:54 AM, "Robert M. Lang" <lang at isis.mit.edu> wrote:
>
> Hi,
>
> I'm not an expert on this, so I'm totally open to ither comments on the
matter...
>
> My first comment would be that it's not clear that a T5 would give any
benefit other than being an inexpensive replacement. For most T5 setups, the
first gear is basically useless for road racing. Because of this, my first
suggestion would be to skip the T5 and think more seriously about a T10. I'm
suggesting this because you're more likely to find a good ratio mix in the
4-speed T10 and T10 knockoffs than with the T5 unless you want to not use
first.
>
> Also, I know we're talking current E Prod SCCA gearboxes here. That means
that you are limited to NON overdrive replacement trannies. Most of the ratio
sets for the T5 that I've seen are 1:1, so that's working in your favor.
>
> That said, all the "successful" Triumph racing gears setups seem to be in
the following range:
>
> 1st   2nd   3rd    4th
> 2.20, 1.75, 1.25,   1
>
> The Dolly Sprint setup is:
> 2.19, 1.57, 1.23,   1
>
> In the T10 world, the T10 c/r sets are in the range:
> 2.20, 1.66, 1.31,   1
>
> If you want a usable first gear for road racing, you need to be closer to
2.0:1, the Kastner first was 1.88:1 - 2.20 is a bit too much gear to be really
usable in anything but the tightest corners...
>
> So, if you found a Muncie "Rock Crusher" aka M22 (I think), you'd be pretty
close to ideal gears, although 2nd is a tad too low compared to that 1.57
dolly gear. If you want, I could chart out the RPM ranges for you.
>
> Now here's the thing: T10's are replicated in NEW gearboxes from everyone,
but Summit Racing sells Richmond Gear T10 4-speeds for about $1800. If you
have more $$$ to spend, then you cannot go wrong with a Jericho and the ratios
that Kastner spec'd back in the day: 1.88, 1.42, 1.24 and 1 which I'm pretty
sure is what Sam H runs in his boxes (plus or minus) - and he can chime in on
that, if he wishes.
>
> The bottom line is that if you are looking for a junk-yard replacement, you
have to make some compromises in the gearing. From my research - that's pretty
much "toss first gear from the mix" if you road race.
>
> Note that wikipedia lists a lot of info on gear ratios for the B/W T5 and
T56, you might be able to use that to zero in on a donor.
>
> Last - there's lots of info out there, but Summit Racing lists the gear
ratios for all the different boxes they sell. They have a number of Richmond
Gear T5 clones and they list the ratios - you may be able to use that info to
zero in on a particular box.
>
> In the spirit of transparancy, I'm also looking at this conversion so I'll
def. keep you posted on whatever I find.
>
> Regards,
> rml
> ---------------------------------------------------------------------------
> Bob Lang              Triumph TR6!!            |  This space for rent
> Former NER Solo Chair                          |
> Voice:617-253-7438                             |  Cell: 339-927-4489
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