Anyone using the Tremec TKX wide ratio transmission?

[Dave Tabor]

I'm considering pairing this transmission with my 3.15 IRS.

Is anyone using such a combination?

Tremec TKX Manual Transmissions TCET18085

https://www.summitracing.com/parts/rem-tcet18085

Thanks,
Dave
Gen III Coupe #17
22,000+ miles

[Jeff Kleiner]

I've considered doing the same for my new build.

When compared to the close ratio TKX coupled with a 3.55 rear the wide ratio TCET18085 with 3.15 rear ends up with a slightly steeper first gear, a bigger step between first and second, longer legs in fourth gear and a deeper overdrive in fifth. For most powerplants I don't feel like those are a bad thing.

Here's the math:
TCET18085 with 3.15 rear
1st (3.27)= 10.30:1 overall
2nd (1.98)= 6.23
3rd (1.34)=4.22
4th (1:1)=3.15
5th (.72)=2.26

TCET17765 with 3.55 rear
1st (2.87)= 10.18:1 overall
2nd (1.89)= 6.70
3rd (1.28)=4.54
4th (1:1)=3.55
5th (.68)=2.41

Cheers,
Jeff

[Dave Tabor]

I've considered doing the same for my new build.

When compared to the close ratio TKX coupled with a 3.55 rear the wide ratio TCET18085 with 3.15 rear ends up with a slightly steeper first gear, a bigger step between first and second, longer legs in fourth gear and a deeper overdrive in fifth. For most powerplants I don't feel like those are a bad thing.

Cheers,
Jeff

Thanks Jeff.

I used to have a 3.55 rear and the close ratio TKO600 with the 0.82 5th gear - I still have this transmission but I'm now running a 3.15 rear.

The car is a bit sluggish off the line but I've become used to it. But now I'm wondering if I can get some of the off-the-line zip back. It's the 1-2 gap that 'might' bother me with the wide ratio TKX - maybe not as I never shift 1-2 on the track once up to speed. Most tracks around where I drive would be run in 2-3.

I'm also after that 0.72 5th gear for high speed rallys - as my car is now (0.82 5th and 3.15 rear) I'm at 5000 rpm at 150 mph.

I use this site a lot:

https://www.blocklayer.com/rpm-gear

close ratio.jpg

Thanks,
Dave

[Jeff Kleiner]

Thanks Jeff.

I used to have a 3.55 rear and the close ratio TKO600 with the 0.82 5th gear - I still have this transmission but I'm now running a 3.15 rear.

The car is a bit sluggish off the line but I've become used to it. But now I'm wondering if I can get some of the off-the-line zip back. It's the 1-2 gap that 'might' bother me with the wide ratio TKX - maybe not as I never shift 1-2 on the track once up to speed. Most tracks around where I drive would be run in 2-3.

I'm also after that 0.72 5th gear for high speed rallys - as my car is now (0.82 5th and 3.15 rear) I'm at 5000 rpm at 150 mph.

I use this site a lot:

https://www.blocklayer.com/rpm-gear

close ratio.jpg

Thanks,
Dave

The 600 has a 2.87 first gear. Combine that with a 3.15 rear and the overall is a soft 9.04:1 overall so it's not surprising that it feels sluggish in comparison to what you had with 3.55s.

Jeff

[CraigS]

I had what I am pretty sure were those gears in my TKO500 w/ 315 irs. I had a 351 and then a 408 so plenty of TQ. When I first did the irs retrofit I thought I might eventually swap to a 331 but I never did and don't think I lost enough to make it worth while.

[stuchman1]

I'm also looking at TKX's currently. Building with gen 3 Coyote, 355 IRS and 15" wheels, which gets ~26" diameter. Not looking to race, rather just driving streets for fun and will put some highway miles on it, and I'd like for my engine to sound happy when we're doing 75 on the interstate.

In reviewing this discussion and others it seems like the 17765 is the way to go, but there have been too many calculations and graphs in the various posts on this topic for me to go out on a limb as a newb and assume I'm drawing appropriate conclusions. Thoughts? Thanks!

tkx.png

[stuchman1]

Sorry - the pasted chart is super small but if you click it, it's reasonable to read!

[rich grsc]

That seems to be good for the Coyote.