Derek,
There are as many opinions on gear boxes, rear end ratios, conversions, and
overdrives as there are people who mess with them. For what it's worth, here is
my own personal view and experience.
Don't know the specified torque rating capacity of your Getrag, or the others,
but
doubt they are in league with a Top loader, which takes on a 427 Cobra with
ease.
The T-5 early models were only 330 ft-lbs and were burned out quickly. They
were
built, I believe, by Mazda for their cars, and adapted by Ford. A "World Class"
version was issued, with a better, but still low, torque capability, of about
380
ft-lbs. The TREMEC is rated a 400 ft-lbs, and is still much lower than a Top
Loader. The T-5 is not renown for it's reliability under stressful conditions,
which is why TREMEC sells. Both transmissions, by the way, are currently built
by
the same company in Mexico. They also acquired the license for the Top Loader,
and built spare parts, although original Ford parts are still available. They
appear to make quality material.
The overdrive (5th) gear of all these transmissions is 0.63, which is
ridiculously
low, and meant only to meet the Corporate Average Fuel Economy (CAFE)
regulations. The engine speed on the highway is quite low, and nice enough, but
you can't use it to accelerate, as your engine doesn't have the power at tat low
an rpm, and the car 'lugs'. A 'good' performance overdrive is 0.8 (a 20% drop
in
rpm from 4th, not a 37% drop (nearly twice - like skipping a gear when
shifting).
All of these transmissions require substantial modification to the transmission
tunnel, and special bell housing, rear support, clutch operation considerations,
as well as nearly impossible to obtain AMC tail stocks for minimizing rear
support
and drive shaft mods
In my personal opinion, there is a better solution.
The Top Loader on the Mk I and Mk IA came with "close ratio" gears. This sounds
good, and is for racing use after the start, but suffer from a speed of 60 mph
in
low gear. This is like starting off in second on any normally geared car, and
it's no wonder people are upset with the 'of-the-line' performance. Most
knowledgeable Ford fans convert these gears (they fit right in) to the "wide
ratio" set. The top gear is still 1:1, but the first gear is moved down to a
much
more usable ratio that gives about 45 mph in first, and gets that Tiger off the
line with a lot of rubber on the road if you don't use traction masters bolt-on
LAT 6 option, (still available new and cheap). A Jaguar Salisbury limited slip
is
a a Dana 44 unit that additionally holds your stock 2.88:1 rear end gears on the
carrier without drilling the carrier holes larger.
The "Wide Ratio" is a misnomer, as the actual gear spacing is quite uniform and
evenly spaced. You will find that a high rpm shift will drop (raise) your rpm
1,000 in a 'close ratio' between any gear set and 1,200 in a 'wide ratio',
depending on whether you are up-shifting or down-shifting. That V-8 just
doesn't
care about 200 rpm at those revs, the torque is still good. This is the
transmission used on the Mk II Tiger and is much better. Cruising at 3,000 rpm
is
72 mph, with slightly larger than original tires (185/70R13's) And the engine
is
quite happy to do this.
Most change their rear end ratios to get better first gear performance, and
suffer
greatly in fourth from 3.56 gears, so they go for a 5 speed overdrive to get it
back down. My personal opinion is that this is like wearing rubber gloves
because
you have a leaky fountain pen.
The Mk II had a 6 bolt engine and two pattern (wide and narrow) bell housing
mounting. The narrow set fits the 5 bolt, and the unit bolts right in. These
may
be hard to come by, and the Tiger mainshaft and tail housing are fairly unique.
You could take yours, and put them in a wide ratio box, or just convert your own
to hold the wide ratio gears - a bolt in! The beauty of the use of a 8 bolt
hole
bell housing attach pattern case is the ease of dropping in a 6 bolt engine, if
you desire. The two patterns are for the two different housings. The only
difference is the front bearing retainer casting is slightly larger on the six
bolt, so you would need to use your 5 bolt case retainer on the rebuild, and
keep
the larger one for a quick change-over if you go with a 289/302. If you are
already there, then all you need is the main shaft and tail stock from a Tiger
or
early Fairlane. These parts are widely available new, and they are not
expensive. A completely rebuilt gearbox might cost you $800. depending on
whether
you had the proper core (tail shaft and tail stock being the significant items.
Do watch out for which internal speedometer drive gear they use, so as to match
your speedometer. The Mk II was different than the Mk I, and who knows what's
on
an other car's box?
Hope this helps.
Steve
--
Steve Laifman < Find out what is most >
B9472289 < important in your life >
< and don't let it get away!>
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