'Found an article in April, 1966 "Ford High Performance",'
April, 1966????, where is Phil LeBrun, the accuracy watchdog, when we
need him?
Jeff
______________________________ Reply Separator _________________________________
Subject: Re: engine/trans compatability ?
Author: Steve Laifman <laifman@flash.net> at INTERNET
Date: 11/3/97 9:46 AM
Carmods wrote:
>
> .How about a Tremec transmission?
>
> Tremec transmissions have torque capacities of 350 lb-ft to 500 lb-ft verses
> 265 lb-ft to 330 lb-ft for the World Class T-5's . the Tremec will bolt to
> Lakewood or Ford 6 bolt flywheel housings. It is however larger than the T-5
> and will require some the additional minor work of widening of the rear of the
> transmission tunnel and modification to the body "X" member for the rear
> mount. Steve, from what you say, I assume the bearing retainer hole must be
> machined in the flywheel housing.
>
> John Logan
John,
No, the larger bearing retainer reference was to Ford/Tiger Top Loader
for the 5 bolt, vs 6 bolt design. All these new ones have the 6 bolt
wider retainer.
With reference to the TREMEC:
Tremec Trading Company
DSA of America
23382 Commerce Drive
Farmington Hills, MI 48335
(810) 471-3200
Dealer Info: (800) 442-8011
I spoke to Julio, who was very informative. My first introduction to
this box was in search of a 5 spd for my Mustang. Most transmission
specilaists warned me away from the T-5 to the "World Class T-5", but
also suggested the Tremec was much better.
Found an article in April, 1966 "Ford High Performance", and acquired
Tremec brochure. There is a basic problem with all 5 speed OD
transmissions, manual or automatic. While the 4th gear is a direct drive
(1:1), the OD is ususally in the 0.63 to 0.68 range. This is quite an
RPM drop. Just multiply the RPM you now have at your cruising road
speed, (say 72 mph @ 3,000 rpm with 185/70 13) and you get a drop to
1890 to 2040 RPM, with these two examples. Drive up a mild hill in your
current top gear, at 2000 rpm, and accelerate from just a little to full
power, and you will get the idea about what your car will be like in
5th, only worse because of tire and air drag. The normal "performance"
OD ratio is 0.8, and this is used in most sports car applications. That
would be a drop to 2400 rpm, in the example. a lot more torque available
here, yet still a comfortable rpm. The reason these manufacturers use
such a low number is to acheive the government decreeed C.A.F.E.
(Corporate Average Fuel Economy), not because it's the good choice for
the car. Tremec says they have a set of "racing" gears available, that
include 0.8 5th.
There are at least two models of the aluminum case Tremec. The standard
is the TR3550, the other is the TKO. Here are the specs:
TR-3550/TKO: 1st - 3.27; 2nd - 1.98; 3rd - 1.34; 4th - 1.00; 5th
-
0.68; Torque (ft-lb) 400/490
T-5/World Class: 1st - 3.35; 2nd - 1.99; 3rd - 1.33; 4th - 1.00; 5th -
0.68; Torque (ft-lb) 265/330
I have been quoted costs of $1125 to $1338 for the Tremec, $1400 for the
TKO, and about $1100 for the World Class T-5.
The TR-3550 has three "top load" covers, and shifting linkages bolt into
any of them, but only the rear comes standard. The center location would
be the one Cobras use. Shift Kits are available to move it. The Tremec
has a 3 1/4 inch spacing between the main shaft and the countershaft,
like our top loader, which allows (and requires) larger diameter gears,
which are also wider. Instead of bushings, like the T-5, the Tremec uses
tapered roller bearings on all shafts, and needle bearings on the speed
gears (like our top loader), and brass blocker rings. The input shaft is
the same dimensions as the T-5, as well as the front bearing retainer.
Unlike the T-5, the Tremec has a positive stop on the clutch teeth of
each speed gear, so the transmission cannot be "overshifted". The input
shaft on the TKO is 1 3/4 inch diameter with 26 splines. The output
shaft is a heavy duty 31 spline that uses a C-6 yoke. The TR-3550 is the
same as stock 302 Ford. The transmissions come with the rear-top mount
shifter, not the side-shift type on our Tiger, and various length and
ratio levers are available, as well as location change kits. The
over-all length of the transmission, from mounting face to end of tail
stock, is 24.07 inches (611.5 mm). The stock rear-most shifter is 19.52
inches (495.8 mm) from the dual 4-bolt pattern front face. The front
face to rear engine mount is 15.8 inches (401.4 mm). The TKO (and
perhaps the TR3550) input spline is 7.47 inches from front mounting face
to end of pilot shaft. I know of early Mustang installation kits that
worry about linkages (mechanical), "adapter plates" for input shaft
length, and revised rear mounts. Some drop the rear mount to clear the
drive tunnel, but this increases the driveshaft angle (not a good idea).
I have seen installations where the floor transmission cover is neatly
cut around the firewall, and down the sides to about the Mustang gear
lever hole. The front of the floor cover is raised a few inches,
allowing a taper back to the end of the long cut. A piece of sheet stock
is welded back in, in a "V" shape alongside the tranny, and around the
firewall. This is very neat, gives the required tranny space without
widening the tunnel, and allows the rear motor mount height to remain
the same. Chevrolet uses T-5's stock, and rotates the tranny
counter-clockwise to position the shifter towards the driver.
I have no interest, financial or otherwise, in any product except our
Air Force/ NASA Space Launch Vehicles. This information comes from Bob
McClurg's article and my phone calls to "Julio". Since I sold the
Mustang and bought the Tiger instead, I have had no hand's on
experience, but all the pro's I've talked to like the Tremec.
I hope that answers your questions.
Since this information is a little over a year old, I would double-check
today's specs and prices. They may have released their 0.8 5th (my
recommendation) for a reasonable price.
Curtis Fisher, <Curtis_Fisher@smtp.svl.trw.com>, asked about ratios with
5 spd, close ratio top loader, wide ratio top loader, rear end ratio's,
etc. He is interested in fast street action and autocross. He currently
has a HiPo 289 with a 3.31 posi. I will try to answer his questions, as
best I know, but realize there are a lot more friends out there who have
BTDT, and should add their 2 cents worth.
1) Calculating speed vs rpm in any set of transmisssion, rear end, and
tire size is relatively simple, and the formulas are available on web
sites and in Tiger Shop Notes. I will send some to you, if you want. The
difficult part is transferring your torque-vs rpm data, tire friction
capability, clutch capability (and your tolerance for replacement) and
drag vs speed data into this model to make selections. My general
comments, based upon my own experience, is that the choice of ratio's is
very camshaft dependent. If your car idles like a wet dog, and doesn't
"fire-up" it's torque until 3500 rpm and above, then that's where you
would want to keep your engine. Choose the combination that keeps you in
that FAT TORQUE range. If you've got a more streetable machine, like the
stock or mildly modified Tiger, then I believe your activities are the
key. For road racing, where you spend your time above 40 mph, the
factory close-ratio is pretty good with the stock rear end and slightly
oversized tires. For around town stop-light drags, and freeeway on-ramp
acceleration, the close ratio gets you about 60 mph in first. This can
put a higher slip in the clutch on rapid take-offs, and you take a while
getting up to the rpm the motor likes. The MKII Tiger, with the "wide"
ratio top loader, is more suited to this activity. Shift speed is about
52 mph, instead of 60, giving you less clutch load (slip) and faster
initial acceleration. Getting out of first at 52 isn't too shabby anyway
(used to be 20 mph in my MG). Since you'll be putting effectively 20%
more torque on the road, your acceleration will be better. Shifting at
about 5-6,000 you get an rpm drop of about 1,000 rpm in the next gear up
(or vice-versa if your downshifting). This keeps the "operating band"
around 1,000 rpm - you choose the band nominal by your choice of when to
shift. The wide ratio will drop about 1200 rpm. This broadens the torque
band, and is ok if you've got a 1200 rpm "good" band. You won't "bog
down" on the shift, and will keep accelerating smoothly if you've got
the torque set up by
cam/carbs/valves/springs/ports/ignition/compression/gas. Trouble is that
adding 20% more torque at dead stop take off is the tires may spin,
getting you nowhere, or you can wind-up the suspension, and chatter down
the road with 1 foot burn marks. I'm sure you've seen that Tiger II
picture. While a Traction Master is supposed to help here, it really is
a poor design. The original doesn't have a good structural connection in
front, although newer replacements do (Tiger Technologies, Sunbeam
Specialties (maybe-ask Rick). Trouble is there are two many pivot points
trying to control your axle, and the harshness of this geometry
competition is harshness when your not on-it, as well. The LAT bolt-on
the spring system is smoother, but the load will shorten your springs
life. The really best solution is Dan Walter's design axle locator,
which only requires two holes (I believe) to install. It locates the
axle with a rigid pair of long arms, is well thought of, but is not
original factory or LAT option (if this is important to you. I would
believe not, considering your use, but I would check with classification
on Autocross events before changing anything that will take you to a
competition level your not prepared for.
I hope this answers your questions, without confusing you more. These
are not simple questions, and require trade-offs only you can make. The
factories spend hundreds of engineering and track testing for each
change they consider, and EVERYTHING is a compromise between what you
want, can afford, and are living to live with the other side of each
choice.
Steve
SORRY about the length, but there were a lot of questions out there.
--
Steve Laifman < One first kiss, >
B9472289 < one first love, and >
< one first win, is all >
< you get in this life. >
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