Which Tremec TKX Do I Get

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srduster340

srduster340

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I plan to purchase the new Tremec TKX transmission to go in my '71 Duster behind a 414 small block with 3.55 rear gears. I want the 3.27 first gear but I'm afraid it might be too much. The wide ratio gear set is preferable because the engine makes a ton of low end torque. I spoke with Jeff Kaufman from SST Transmission and he stated since I have 27560R15 tires my 3.55 is more like 3.23. Now this is a street car not a track car. I'm kinda indecisive right now and need opinions.
 
srduster340 said:
It's a P27560R15 on the rear.
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That is 28" in diameter. Stock was approx 26".

upload_2020-12-22_9-7-23.png
 
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srduster340 said:
I plan to purchase the new Tremec TKX transmission to go in my '71 Duster behind a 414 small block with 3.55 rear gears. I want the 3.27 first gear but I'm afraid it might be too much. The wide ratio gear set is preferable because the engine makes a ton of low end torque. I spoke with Jeff Kaufman from SST Transmission and he stated since I have 27560R15 tires my 3.55 is more like 3.23. Now this is a street car not a track car. I'm kinda indecisive right now and need opinions.
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I got a qoute from American Powertrain for a complete TRX conversation kit, auto to manual, right at $5500 shipped.
I also favor the 3.27 gear with that tall of tire
 
Should be worth it no matter the cost. Manual trans are just so damn fun. They fit my personality perfectly. LOL

im looking forward to your progress !
 
512Stroker said:
I got a qoute from American Powertrain for a complete TRX conversation kit, auto to manual, right at $5500 shipped.
I also favor the 3.27 gear with that tall of tire
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5000.00 ? What all does the include ?

Can you use the exhisting clutch , pressure plate and flywheel ?
I have a couple grand in my Mcleod setup currently
 
mbaird said:
5000.00 ? What all does the include ?

Can you use the exhisting clutch , pressure plate and flywheel ?
I have a couple grand in my Mcleod setup currently
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I’m pretty sure the tkx has a 26 spline input shaft as opposed to the 23 spline a833.
 
512Stroker - did they say it will fit without cutting up the floors?
 
How much could it cost to machine a few various input shafts ?
Out put yokes are relatively cheap and driveshafts are easy to shorten so I understand not having too many variables there . It wouldnt be that hard to make a near direct drop in trany and they would sell the Bajeezes out of them if they did .
 
mbaird said:
5000.00 ? What all does the include ?

Can you use the exhisting clutch , pressure plate and flywheel ?
I have a couple grand in my Mcleod setup currently
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They offer two differant kits
One kit converts auto trans to 5 speed manual, it comes complete clutch, bellhousing, TKX, driveshaft, peddle set, cross member, the works. - $5500
The other kit converts from 4 speed to 5 speed TRX. Price $ ?
Contact them I think they will sell you what ever you want.
 
mbaird said:
5000.00 ? What all does the include ?

Can you use the exhisting clutch , pressure plate and flywheel ?
I have a couple grand in my Mcleod setup currently
Click to expand...

I used most of mine for my TKO Swap, just change the disk out to a 26 spline. I have a McLeod Flywheel and clutch too. This is if you get the TKO bell for a Ford which used the 72-up Z-Bar pivot. Even my stock drive shaft was the correct length, just bought a conversion u-joint for the output yoke. I think I was $3300 including trans into my swap. I have a Hurst kit which they no longer make but still sell the mounts the last I knew. Rebuilding the tunnel is most of the work, hopefully the TRX limits that.
 
Ok .. I understand now . I thought we were talking about the new 5 sp.
 
mbaird said:
Ok .. I understand now . I thought we were talking about the new 5 sp.
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I believe we are, the TRX is a drop in for the TKO except with less tunnel mod work. Hopefully its a matter of a few notches and some strengthening plates on the stock torsion bar hoop for the TRX vs remove and replace and widen the tunnel for the TKO.
 
Question on the first gear ratio, with out getting into the drag race starting line ratio. Another reason for picking the 3.27 first gear for a streetcar is the lower gear will keep you from constantly riding the clutch at low speeds in slow moving traffic, such as getting in an out of fairgrounds for car shows, traffic jams, or any place where you would be putting along at 5 mph or less. Save yourself a lot of wear and tear on your clutch and leg and in a streetcar with a high torque engine that wide ratio between first and second won't be nearly as bad as most would make you think. Those 4.6 and early 5.0(302) mustangs never seemed to have a big problem with the wide ratio T5 and TR3550 they ran.
 
The caviat to that scenario is that the reason to go to it is because of the O.D. so you can run low gears and not be turning 4k @75 mph.
So if you are using 3.55/3.91/4.10 gears your 1st will be like a John Deere ! That could get old and would suck at the strip.
 
mbaird said:
The caviat to that scenario is that the reason to go to it is because of the O.D. so you can run low gears and not be turning 4k @75 mph.
So if you are using 3.55/3.91/4.10 gears your 1st will be like a John Deere ! That could get old and would suck at the strip.
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My dad did just that with a 5.0 Mustang. Put 3.73 and a Tremec 3550 (pre TKO stuff) in with the 3.27 1st and it was useless unless you wanted to rock crawl over speed bumps. He switch to 3.27 and it was a much better car. But it didn't have a 28" tall tire either.
 
19DART66 said:
Those 4.6 and early 5.0(302) mustangs never seemed to have a big problem with the wide ratio T5 and TR3550 they ran.
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A lot of those early manual trans 5.0 cars has 2.73 gears, 3.08 if you were lucky. The 4.6 cars had 3.27 but didn't have the low end torque of the 5.0 but they would spin higher. There are exceptions to special cars like the Mach 1, some Cobra's and auto cars.

I had a 92' GT withe 3.08 and a 3550 with a 3.27 1st and it was a good match, mainly because the 3550 was designed to replace the Mustang T5 and was used in the 1995 Cobra R.
 
mbaird what first gear ratio do you run at the strip and how bad are your 60 foots. dano the quicker mustangs at the track all ran those transmissions with a minimum of 3.73 rear gear. Your cruise rpm and fuel economy will be based more on were your engine rpm wants to be, for instants I bought a new Durango in 2003 with a 4.7 and 3.55 gears, it had the 265/70/16 tires on it. At 65 to 70 mph it wood get 15 to 16 mpg at 85 to 90 mph it wood get 20 to 21 mpg, that engine preferred to run at over 2000 rpm than under 2000. I have an Eco Diesel truck with 3.55 gears now and that gets its best mileage between 55 and 65 mph at 70 and over it drops 2 to 3 mpg, it prefers to be under 2000 rpm's. Every engine is different and the engine will dictate were its best efficiency is not the gear ratio you think it should be. My Dart smooths out, quiets down and pers like a kitten between 3000 and 3200 and that is its efficiency rpm range, it's between 60 and 63 mph.
 
I prefer the wide ratio T56 gear set with 2.97, 2.10,1.46,1.00, .80, .63. I actually wrote to Tremec about why not make a modular mounting plate with multiple bolt patterns, bearing retainers to mount to a Mopar, AMC, etc. We'd only have to change clutch disc. Of course they directed me to one of their many distributors like that's gonna do any good. I think the "safe" bet is the 2.87 first gear for me. That .68 OD will make my 3.55 a 2.41. I could hit 80mph @2300! Right now I run 60@2600.
 
19DART66 said:
Question on the first gear ratio, with out getting into the drag race starting line ratio. Another reason for picking the 3.27 first gear for a streetcar is the lower gear will keep you from constantly riding the clutch at low speeds in slow moving traffic, such as getting in an out of fairgrounds for car shows, traffic jams, or any place where you would be putting along at 5 mph or less. Save yourself a lot of wear and tear on your clutch and leg and in a streetcar with a high torque engine that wide ratio between first and second won't be nearly as bad as most would make you think. Those 4.6 and early 5.0(302) mustangs never seemed to have a big problem with the wide ratio T5 and TR3550 they ran.
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I'm not concerned with the gear split but the 3.27 first gear multiplied by the 3.55 rear axle gear winding out to fast like a granny gear. You get a 11.60 overall first gear with the 3.27, a 10.18 with the 2.87 first gear. Stock 2.66 you get a 9.44.
 
Yes the same as my 2012 Challenger R/T 6 spd, with a 2.97 first and 3.92 rear gear(11.64) and even that first gear is to high when stuck in traffic. When drag racing with a stick car you want your starting line(first gear) ratio to be between 13.0 and 15.0 for best launch and 60 foot. I run a 3.04 first and a 4.10 rear in my Dart which is a 12.46 first, I am slipping the clutch at this ratio more than I should to put down 1.50 60's. The Dart would work better with a 4.30 rear gear(13.07 first) and put the engine right around 6500 rpms in the traps(some day the 4.30 will go in), hell it's only another 160 rpm at 65.
 
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