Transmission selection dilema

My engine build target completion is late October.

The new engine specs will have torque numbers that exceed the ratings of my T-45 5 speed (which is like new.) 615 hp 550 tq Torque is at 400 ft pounds at 2000 rpm and just goes up from there.

As an alternative I have the 4 speed Toploader that I removed and rebuilt with a David Kee Road Racing rebuild kit. I believe it is more than adequate for the power levels. I also have a relatively newer Hurst shifter that is in excellent condition.

The T-45 also has an unnecessarily steep 3.37 1st gear ratio as compared to the wide ratio Toploader's 2.79 1st gear ratio

I have drive shafts to fit either installation and cross members for either as well. Clutch assembly is the same and I have a Lakewood bellhousing to fit either as well as a ford bellhousing that will work with either.

The Toploader will require a milder rear end ratio than the current 3.91-that is the only significant expense I will have to incur if I go with the toploader. Even at that the 3.91 gears are fine for 90% of my driving, so I could wait on that until I have everything broken in.

Keisler told me their transmission was rated for 400+ ft lbs of CONTINUOUS torque and that it could handle more on an intermittent basis.

I'm running a Kevlar clutch, though that may change. Right now I am concerned that my transmission is the weak link and I don't want to go through having my car down again.

I am looking for all thoughts on the best solution. I care about money, but not as much as doing it right.

Far from a genius but what size tire are you running? The only thing that I didn't see mentioned which can vary those gears a reasonable amount.

Personally I am fan of the Top Loader it is a good trans that can take some reasonable punishment especially with good rebuild parts. Under normal DD activities I wouldn't think you would be pushing it that hard. Track day activities though I could definately see.

Almost sounds like you need a few different geared center sections laying around......

Like me with 3.50, 3.70, and 3.91's in the garage

255-40 17's for the time being-I figure they are the true weak link, but if I put anything bigger and they dead hook-something will break and I don't think it will be my 31 spline axles

One thing I will never get over is the tire size used on Mustangs in general. Coming from the performance truck sect(Ford Lightnings/ Harley F150's). We are used to running 295's, 305's, 325's and such. Lots of contact patch for the torque.

Just the thought of 275/60r15 is alot of tire for many cars.

Jeff I've never like the dump truck first gear ratio in a T-45. I vote TKO-600 all the way.

TKO-600 gears:

TKO600 2.87 1.89 1.28 1.00 0.64

Assuming 26" tires...With a 3.91 rear it would give you a decent overall first gear ratio of 11.22:1. You mph at 7000rpm in 1st would be 48.3mph.

For comparison

Currently with the T45 you have:

T-45 gears: 3.37 1.99 1.33 1.00 0.67

Overall first gear ratio is 13.18:1 which as you know is useless.

Toploader

4 spd Toploader gears: 2.78 1.93 1.35 1.00

Overall first gear ratio is 10.87:1. Which is in the perfect range (9-11) IMHO.

However, 4th gear RPM at 75 MPH is 3,790 rpm. Would sound great though!

Jeff,

The 2014 Shelby 1000 sports 1200 horsepower at the flywheel; figuring that the upgraded six-speed manual transmission saps has a driveline loss of about 15 percent, we’d predict that the 1000 S/C makes between 1020 and 1050 horsepower at the wheels. Shelby didn’t release any acceleration or top-speed figures, but we’d predict that they’re somewhere between “oh wow” and “holy crap.”

http://wot.motortrend.com/shelby-gt500-based-shelby-1000-sc-has-1200-hp-345149.html#axzz2gUxkxiF0

Trying to find out about the Shelby 1000 transmission specs. has been a bit difficult. The articles states that it is a beefed up six speed. Expensive, anybody! We all know the Top loader 4 speed is a great transmission, but, with today's technology, there has to be something out that can handle your specifications.

White Knuckled Driving Shelby 1000

mustang7173

Mmm, Tremec is your friend in this case

I was just reading some reviews on that TKO 600 and it gets some real nice reviews. How hard would it be to bolt one into our Mustangs as far as fitment goes.

It is definitely doable, though the tunnel is probably going to be a bit tight. My concern with the TKO series is poor high rpm shifting. That may be a thing of the past though.

Here is one http://www.summitracing.com/parts/fms-m-7003-r58c that isn't priced too badly-but add a clutch and pressure plate and yoke and altering/replacing a driveshaft and that is still 3K and I'm not sure I can afford that right now.

It is definitely doable, though the tunnel is probably going to be a bit tight. My concern with the TKO series is poor high rpm shifting. That may be a thing of the past though.

Here is one http://www.summitracing.com/parts/fms-m-7003-r58c that isn't priced too badly-but add a clutch and pressure plate and yoke and altering/replacing a driveshaft and that is still 3K and I'm not sure I can afford that right now.

Click to expand...

There are fixes for the third gear shift issues.

Sell the t45 and toploader and go with the tko 600

Based on your cited power level and what you have already done with the Top Loader, Jeff, I would actually go with the Top Loader.

Just my $.02.

BT

Just wondering, can the T45 first gear be changed out to a different ratio?

I've put the toploaders through a lot of abuse. Some intentional and some not. I wasn't however running your set up Jeff. But I still think toploader to start, refine later.

I've put the toploaders through a lot of abuse. Some intentional and some not. I wasn't however running your set up Jeff. But I still think toploader to start, refine later.

Click to expand...

+1. Good idea Mark - cost effective too since he already has one and it will do 90% of what he wants to do with the car. I didn't think about it in those terms of swapping it later.

I am leaning towards the toploader at this time. I am going to wait until I see the actual dyno runs before I panic too much. I can always change my cam to one that is milder if necessary.

Since we're spending YOUR money... Jerico! Clutchless shifting and nearly indestructable. Then, upgrade the rear end, driveshaft, clutch, suspension... etc.

I ordered a Jericho this morning . . . . lol

Jeff,

i kinda ran into the same problem a little while ago,.. 1 of the first things i asked myself, how much do you actually use the car?

for me , i have a company van, so dailydriving is out of the question ( the van is filled with tools/parts ) and i only use the car for recreational purpose,.. so, is it then worth it to put in almost 3K for just a few lower revs on the highway,.. because that the only thing that makes the difference,.

now over here , i dont have to drive that far for a cruise or meeting. so what i did is put in a lower gear,. i went from a 3.89 to a 3.70,.. i have 285-40-17 tires,.. it still breaks them loose with ease, so don't worry about that..

i stayed with my Toploader,.. its durable, it can withstand lots of abuse,. if you wanna go 5 speed, , in your case/ engine, i would go TKO600..

for me, i would trust it to place a build T5 behind it.. my engine only makes about 400-450hp,.. but i dont do dragracing, so breaking the trans because of to much grip is out of the question.. and i dont ride it that hard,.. but if it blows,.. theres only 1 to blame and thats me..

there are lots of stories out there of guys putting t5/45's behind pretty stout motors on the strip, and staying in 1 piece. some blow up,.. even a TKO 600 can blow up..

my 2 cents

If this is going behind a SBF bellhousing pattern I wouldn't waste my time with anything other than a Tremec. You can choose a TKO-600 or a 3550 with the right parts, but you won't go wrong with a Tremec in there. I've been abusing my 3550 with 730 crank hp for years and the transmission hasn't complained. I've munched a few rear ends (literally crushed the main support bearings in an 8.8), but the transmission is going strong.