Re: [Amc-list] Reasons To Use a T-5 and Why?

[adh@xxxxxxxxxxxxxxxxx (Sandwich Maker)]

" From: "John Elle" <johnelle@xxxxxxxxx>
" 
"  
" SNIP 
" " If I had the money and the inclination there are gear sets that would
" " enable me to change the gear ratio of 1st and 2nd to give me a closer
" " to a close ratio 4 speed with a deep over drive which would have
" " done 2 things.
" " Let me keep the 3.54:1 rear axle with out changing
" " it and strengthened the transmission to specifications approaching
" " those of a T-10.
"  
" if you want strong and close ratio, g force and 1 or 2 others have t5
" road racing gearsets which they claim can take 600 hp...  i don't
" think they're worth it unless you're road racing.
" SNIP
" Here is where the major application differences start to show up. It 
" is almost of no significant importance what so ever as to what the 
" gear ratio of 5th gear is. 

this is true, but the g force set is all the gears.  iirc 1st is about
2.43, 5th is about 0.93.  made of strong 9310 nickel steel and $$$$.
not for you if you want a deep o/d.

" That application of the transmission on an earlier muscle car or 
" equivalent is to extend the cruising range on the highway. To whit 
" to give you a 4 speed transmission with a deep overdrive to reduce 
" engine rpm on the open road to increase fuel mileage. 

some of us would like all 5 gears, eg. -not- a -deep- overdrive 5th.

" The Mustang 5 speed was installed in pony cars of the time as just 
" that sort of compromise transmission.
" []
" One of the most reliable ways that can be done is to reduce engine 
" rpm at cruise speeds. This can be done by adding a 5th gear as an 
" overdrive to an existing 4 speed transmission. 4th is still 1:1 for the
" most part but 5th will be typically in the area of .75:1 or so. Why that
" number I don't know as real overdrives were typically 33% or so. 
" Maybe perhaps that is all the room they had in the transmission to 
" put gears in to.

fwiw 5th in the ford 2.95 t5 ['83-5 mustang, svt '7003' series] is
0.63; in the '86-up mustang 3.35, 0.68 with v8s and 0.73 with v6s.
in camaro/firebird 2.95, 0.73.  ironically the tallest 5th are on t5s
with the tallest 1st too, but maybe not a coincidence they're all
teamed with big [for the era] fuel-hungry v8s.

btw in the t56 both 5th and 6th are overdrives, with 6th 0.50.  iirc
1st is 2.66.

the warner r10 o/d is 0.7:1.

" However to get 5th gear into the 33% range one can 
" put a taller rear axle in. Say change a 3.50:1 to something like a 
" 3.07:1 or even a 2.90:1 (High 2's to Low 3's). After all engines of 
" the time had more power than engines of the 50's and could pull 
" taller gears easier in high (usually defined as a gear ratio of 1:1). 
" Now a 1970 AMC T-14 had a gear ratio in first of 2.6:1. 
" if you round everything off to the closest
" tenth and a T-10 4 speed had a 1st gear of 2.23:1 in one of it's 
" permutations 
" there were 4 or so that I am aware of but 1st gear would not be 
" too far away from that. 

2.23, 2.43, and 2.64 in amcs.

" Most 3 speed transmissions were installed in heavy cars with 
" underpowered motors 
" []
" Where as a 4 speed was usually installed 
" in something that might be the same weigh less or with 3X the
" motor in it which would definitely be able to move a car from 
" a dead stop quickly.

random data points: a '68 american with 232 and t-14 weighs about 2700
lbs; a '68 javelin with 343 and t-10 is about 3100.

" By installing a performance axle such as 
" something short in the middle to high 3's acceleration would be 
" enhanced and fuel economy would get worse. 
" 
" Now for the Ford Mustang, if the 5th gear was in the area of .75:1 
" or 25% the only way to get it to act as if it was .66:1 or 33% would 
" be to install an economy axle ratio (tall ratio) in the high 2's. 

it's already 0.68:1.  standard axles were 2.73 and 3.08.

" Once it was in 5th engine rpm would be reduced, fuel economy would 
" be improved
" However the 2.23:1 1st gear ratio was going to be a problem as 
" the rear axle ratio was far too tall to allow any performance at all. 
" (As a side bar to this I replaced the 3.54:1 axle in my Javelin with 
" a 3.15:1 rear axle and then proceeded to go through 3 clutches)

got a bit of cam, eh?

3.55 and 3.73 are popular swaps into the 'stang, even with the 3.35
1st.  but then even the drag racers are mostly running only a 302.

" Thus the solution would be then to shorten up the first gear ratio 
" (and related other ratio's) to allow rapid acceleration. 
" So thus 1st gear of the Mustang T5 became 3.35:1 (in one permutation) 
" to compensate for the economy rear axle. 

this is the second tallest 1st gear used in any sr4/t4/t5.  the
tallest is 2.95.  all the others are 3.50 or shorter.

" These gear ratio's as applied to the Mustang for the W/C applications 
" and I am sure others if applied to a 1950's vehicle with the typical 
" rear axle ratio of the time, 1st gear would be defined as a Granny Gear
" commonly found in Trucks.

not as wide as a real truck tranny, but definitely overkill with the
low speed torque of '50s engines.

" Unfortunately those of us with muscle cars with the objective of
" installing 
" an overdrive to reduce engine rpms at freeway speeds, quickly found 
" out that in first gear the car suddenly drove like a John Deere Tractor.
" 
" How do you fix it? 
" You can search the parts bins and see if you can find a tall AMC axle 
" in the high 2's or low 3's that will mimic the Ford application. 
" Thus it is not important to determine what the precise exact value of 
" 5th gear is. It is an overdrive. 1st through 4th (1:1) becomes a wide 
" ratio 4 speed and the taller rear axle in the car completes the package.

it does matter, if the axle that renders 1st usable makes 5th too high
to pull even on the highway.

" SNIP
" btw everyone - hp doesn't matter to a tranny; they're rated on torque.
" the tremec john mentions above, and the toploader it descended from,
" are the kings in that respect of all the trannies we've tossed about.
" SNIP
"  
" While this is technically true, transmissions are rated in torque
" applications, 
" I personally build horse power engines which as a by product of horse 
" power they will generate torque.

true, but 400 hp doesn't guarantee 400 ft-lbs; it depends on the
displacement, rpm, etc.  that was my point.  a big '60s v8 that made
400 hp might have almost 500 ft-lbs, but a recent bmw v8 that makes
400 hp has little more than 300 ft-lbs.

" ... if I were to build a Purpose Built 
" 400 HP drag racer, and budget was not a problem I would go with the 
" TREMEC. 

is there really enough time to go through all 5 gears in a 10s
quarter?  that's why i thought an iron case 4sp toploader would be a
good solution, much cheaper than a tremec and stronger than a t5.

" ... there is a very 
" important point here I am trying to present in choosing a 5 speed 
" transmission to back fit into your AMC muscle car. 
" It makes almost no difference whatsoever what 5th gear is! But you had 
" better pay very close attention to the gear ratio of 1st gear as you 
" may be very disappointed in the final result. 

i'm not sure 5th is all that unimportant, but i agree 1st is.  that's
why i don't see an ax-15 in a car as much of an idea.
________________________________________________________________________
Andrew Hay                                  the genius nature
internet rambler                            is to see what all have seen
adh@xxxxxxxxxxxxxxxxx                       and think what none thought
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