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

["John Elle" <johnelle@xxxxxxxxx>]

SNIP
" I  have already installed one Mustang Transmission and have driven
" it behind a cooking version of a 390 for about 15 years now and
" really have no complaints.
 
street driving or quarter miles?  the original poster wanted to get
into the 10s in his 343 powered '79 amx.
SNIP
Street racing, occasional drag strip, cross country touring, doing
stupid
things and  general just enjoying my self. This is on top of the orginal
110,000 miles that was on the transmission put on by both owners of
the Mustang it came out of. Until it was wrapped around a tree. I have 
put an additional 25,000 miles on it in my Javelin. 
This should be at least one example that the transmission is reasonably
capable of taking a fair amount of abuse as designed and certainly is
what the thing has a reputation of doing. However there are a number 
of relatively inexpensive modifications that can be easily done to it 
to improve it's performance of which I have only done one of them. 
 
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. 
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. 
This is as a substitute for attaching an overdrive that was common 
on American automobiles from some where in the 1920's up through
the early 70's. 
It is even my understanding if you have a large enough parts bin you 
can remove the tale shaft of a T-10 and replace it with an OEM over- 
drive tail shaft from a similar 3 speed that the T-10 is based on if 
you had the parts or could find them. Or if you have a pocket deep 
enough you can purchase a Gear Vendors overdrive unit and install
it on the rear axle. This gives you the capability of having drag racing

gears and economy gears on the same car. 
 
I am referring to a multi-purpose automobile, one which will see 
multiple applications, not a purpose built drag racing or any other
of race car. 
 
The Mustang 5 speed was installed in pony cars of the time as just 
that sort of compromise transmission. The operative word is 
COMPROMISE!
The need of OEM was specifically to give GOOD performance if 
not in reality but as an illusion AND good fuel economy. 
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. 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. a T-15 
of about the same as a 2.6 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 and that depended on which model T-10 you had, 
there were 4 or so that I am aware of but 1st gear would not be 
too far away from that. 
 
A 2.6:1 is shorter than a 2.23:1 for a reason. Most 3 speed
transmissions were installed in heavy cars with underpowered 
motors and you had to have more oomph to get the thing moving 
from a dead stop. 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.  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. 
Once it was in 5th engine rpm would be reduced, fuel economy would 
be improved and you can have your cake and supposedly eat it too!
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)
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. 
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. Useful only for pulling tree stumps out 
of plowed fields.  This transmission now can be considered to be 
a wide ratio 4 speed transmission with a deep overdrive attached. 
 
Once Ford got all of this straightened out it worked to the benefit 
of AMC people in that the transmission was easily installed in almost
any AMC car, a bolt in application using a composite of AMC and Ford
components. 
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.

 
Snip
thanks to jeepers, 3.31 and 3.07 are also available...
 
" Considering the  3.35 of the FORD camp -
 
remember there's also the 2.95 ford svt t5.
Snip
 
My experience says that a 3.15:1 AMC rear axle ratio is too short 
for a really useful 1st gear application. However for me, there is 
enough cam in my engine that the  3.15:1 rear axle makes driving 
the car in 1st in city traffic easier. 
If I had my druthers I would prefer the taller 3.07. I would not even 
consider installing a shorter 3.31:1
 
Along with some simpler modifications there are gear sets available 
for the Ford T-5 which will give you something closer to a 2.25:1 
1st gear ratio. 
The advantage (along with technology and materials) of a taller 1st 
gear ratio is that the multiplication factor of the gearing decreases
the 
torque rating capability of the transmission the shorter 1st gear is.
Thus 
if you can installer a taller first gear assembly the torque rating of 
the transmission will improve by definition and approach the ratings 
of a T10.
The only thing any of this needs is money, luck to be able to locate 
what you want and more money. Some of us have to make do with 
what we have at the time and go from there. 
I installed my T-5 in my Javelin around 1995 or so after I had lunched 
the T-10 turning it into no speeds forward and erratic reverse. I looked

for 4 months for a T-5 I could afford at the time and bought the one 
that became available. I installed it, it works fine and it is still
there. 
and it still works fine. 
 
SNIP
street driving or quarter miles?  the original poster wanted to get
into the 10s in his 343 powered '79 amx.
SNIP
 
Now for this application, 
Snip
" Now if I really intended to abuse a 5 speed with a 400+ horsepower
" engine I might be inclined to obtain a 150T bell housing and install
" a (Mustang application) Tremec which definitely would take the abuse.
Snip
This would be certainly a way to go that will lead to success. 
Another option would be to rebuild a Mustang W/C T-5 with all of 
the performance updates my guess it would be cheaper than the TREMEC 
but not by much. 
 
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. But my engines perform for me in the 
manner that I want them too and if I were to build a Purpose Built 
400 HP drag racer, and budget was not a problem I would go with the 
TREMEC. 
 
Now if I were to build a purpose built sled pulling tractor I would be 
very much interested in the amount of torque my triple turbo-ed diesel 
international running on alcohol would develop. But I wouldn't be using
a TREMEC. 
 
O.K., It's wordy, if you don't like it don't read it, but 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. 
John. 
 
 
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