TKX or Magnum in 70 Nova

[Steel409]

Hey all!



I'm ready to make the transition from a TH400 to a 5/6-speed transmission. I have a Blueprint Engines 383 (405 hp/440 tq), and 3.73 rear end with 26.65" tall rear tires. I'm going back and forth with SST on a TKX (.68 OD) vs. Magnum (.80/.63 OD). I initially wanted the 6-speed, but am wondering if the 5-speed might suffice for me. The 6-speed made sense for 75-80mph highway cruising around the state of WI. Car will be street/highway driven with occasional sprint around the autocross if the situation presents itself. I'm also interested in an LS swap a few years down the road and would prefer not to buy another trans. Anyone make one decision on a 5 or 6 speed and wish they had gone the other way? Given my parameters, any feedback would be great from folks that have lived it. It's an expensive decision!! Many thanks, in advance.

[Just 1 More]

I wrestled with this same decision and went T56 Magnum and love it, no regrets. The 5th is great for that 55-65 cruising and then 6th for the 70-80+, The 5th gear makes for a nice step rather than jumping from 1:1 to a .63

[Pro Touring Store]

Often times there is tunnel modifications needed for the T56.
The .68 and .63 are so close that highway cruising RPM is different by 150rpm. That shouldn't be enough to sway one way vs another.
If your cam allows, the wide ratio .5 is nice for cruising 80mph.

[Just 1 More]

Often times there is tunnel modifications needed for the T56.
The .68 and .63 are so close that highway cruising RPM is different by 150rpm. That shouldn't be enough to sway one way vs another.
If your cam allows, the wide ratio .5 is nice for cruising 80mph.

IMO, there's a lot more to consider than just the finale drive ratio.. How many times are you actually going to want to jump from 1:1 to .68 or .63? You'll find the .80 step much more useful and easier on the lugging of the engine with the drop in RPM from 1:1 to .68 or .63. I spend a lot of time in 5th .80 than I do in 6th or what would be 5th on the 5sp. The 5th and 6th add what I would consider "Driveability"

[Steel409]

Thanks, all. This was the exact conversation I needed to help make a decision.

Good point. If the difference between the TKX and Magnum at 80 mph is 188 rpm's, what does upgrading to a 6 speed get you? More shifting? Beneficial for autocross? The shop that will do the work recommended the TKX, but I'm looking at WI expressways at 75+mph, so am looking forward to the trips.

Fair point about final gear rpm's... I don't want to compromise 1-5 just to get double OD at .63?

What am I missing?

[Lonnies Performance]

I have both in different cars.

TKX
What I like...
Ease of fitment with no floor cutting.
Similar OD ratio to the T-56 Magnum in high gear, for highway use.
Works with stock manual clutch linkage & belle housing.

TKX dislikes...
Too low of a first gear.
Would like a tighter gear spread.
5th gear is a big drop & not really suited for maximum acceleration. drops from 7000 to 4800 on a gear change.
In case you didn't notice, my only gripe if the gear ratio selection... If I had my choice, I would take a TKX using T56 Magnum ratios with a missing 5th gear.

T56 Magnum likes...
Excellent gear spread less rpm drop between gears.
Direct fit to an LS engine with factory slave cylinder & parts.
5th gear is another "gear" with a reasonable step from 4th if you want to stay in it longer & not just for cruising. 7000 to 5800 on a gear change.

T56 Magnum Dislikes...
Heavier
Better suited for a hydraulic clutch
May require floor modifications.

I've found that 4.10's are too much 1st gear for the TKX in my opinion but 4.10's with the T56 is a great combination for a moderately powered vehicle if drag racing (using 4 gears up to about 135mph), with 5th available for more top end.

3.73's seem like a good compromise for both & you would not need 5th under power unless in the 140mph+ range.

[F-Body International]

I personally would do a TKX but many pro-touring people like the 6spd. My reasons would be TKX uses the traditional style bellhousing, is lighter (easier for working on the car) and easier to fit in any chassis due to being a smaller case.

You know what you’re looking at. Pick what you feel is best for your build. I’m just over the border in IL. I completely understand you about the WI roads. I go to Lake Geneva and sometimes Milwaukee in the summer and the road’s definitely open up once I cross the border.

[Olds.PhD]

I've not used the TKX, but can echo what others have said about the T56/Magnum: that 5th gear is real nice to have. Freeways around here run 75-80 mph, so the deep final overdrive is necessary to keep RPMs reasonable. That leaves a hell of a drop from 1:1. I actually spend a lot of time in 5th - way more than I thought I would.

Tunnel modifications also aren't that difficult. I had to cut a substantial portion of my floor, and found SilverSport's template to not work well in my car for whatever reason. So I was on my own for the tunnel. It took me awhile, but it wasn't difficult.

That said, I understand being averse to cutting up a car - in which case I think the TKX is a wonderful second choice.

By the way - super happy with SST's customer service. Absolute top-notch. Hopefully you'll have the same experience.

[BobinFL]

I too vote for the 6 speed. 5th gear is ideal for that 45-60 mph range, where .63 is just too much of a drop in rpm and my engine can struggle. 1,800 rpm and up it is a happy camper. I also like the evenly spaced ratios in the lower gears. Feels a lot like shifting my old close ratio Muncie.

[mikedc]

Different opinion -


God didn't give Moses a commandment that 5spd trannys must have a huge gap between 4th and 5th. People order them that way by choice.

Compare a TKX with the lower 3.27 1st gear + .72 or .81 overdrive . . . the overall spread is almost the same as the typical Tremec 6spd Magnum (2.66 1st & .63 6th). But the drop from 4th-to-5th is reasonable.

What's the downside for a street cruiser? One less gear in the 0-40 mph area? That fails to bother me. In fact I like it better.


BTW Tremec's wide-ratio lower gearset for the 6spd is inferior to their 5spd wide gearset. It's a 2.97 1st and a goofy wide gap from 3rd-to-4th.


Try messing with a calculator. Google search for "blocklayer rpm gear". It visually graphs the rpm drops.

[Olds.PhD]

What's the downside for a street cruiser? One less gear in the 0-40 mph area? That fails to bother me. In fact I like it better.

0-40 is 1-4 with both transmissions. Literally no one on this thread was talking about the extra gear helping there. Com'on. You can make your point without being disingenuous.

[mikedc]

0-40 is 1-4 with both transmissions. Literally no one on this thread was talking about the extra gear helping there. Com'on. You can make your point without being disingenuous.

0-40 is only 1st-to-4th if those bottom gears are close ratio. If it's a wider ratio then you may still be in 3rd gear when you hit 40 mph. That's what I meant.


The setup that I'm suggesting is wrong for a competitive track car. But the OP isn't building that. He said: "the car will be street/highway driven with occasional sprint around the autocross if the situation presents itself."

[Olds.PhD]

0-40 is only 1st-to-4th if those bottom gears are close ratio. If it's a wider ratio then you may still be in 3rd gear when you hit 40 mph. That's what I meant.


The setup that I'm suggesting is wrong for a competitive track car. But the OP isn't building that. He said: "the car will be street/highway driven with occasional sprint around the autocross if the situation presents itself."

He's already got 3.73s and all of the transmissions are 1:1 in 4th. The only way that comment makes sense is if he swaps his 3.73s for 2.80s to run the wide ratio TKX.

Personally, I'd go with the lighter weight TKX for track, given there are very few tracks you'd actually manage to hit 6th gear in, but everyone has their own preference.

[mikedc]

He's already got 3.73s and all of the transmissions are 1:1 in 4th. The only way that comment makes sense is if he swaps his 3.73s for 2.80s to run the wide ratio TKX

Yeah, 2.80 sounds about right. A gear swap is a gear swap.


The setup I'm suggesting (tall axle gear + wide-ratio trans gears + deep 1st ratio) is normal OEM stuff in a sporty touring sedan from Germany or Australia. It only sounds bizarre to the muscle car hobby.

[vcho455]

Yeah, 2.80 sounds about right. A gear swap is a gear swap.


The setup I'm suggesting (tall axle gear + wide-ratio trans gears + deep 1st ratio) is normal OEM stuff in a sporty touring sedan from Germany or Australia. It only sounds bizarre to the muscle car hobby.

"Compare a TKX with the lower 3.27 1st gear + .72 or .81 overdrive . . . the overall spread is almost the same as the typical Tremec 6spd Magnum (2.66 1st & .63 6th). But the drop from 4th-to-5th is reasonable.'

I've argued for this combination lots of times. It's a close approximation of my old Doug Nash 4+1 set up. Which for me was great.

I am a fan of the blocklayer gear calculator too.
https://www.blocklayer.com/rpm-gear
I also like the calculator at the Weddle Industries site.

https://weddleindustries.com/gear-calculator

[TANKMASTERJ]

I have the magnum wide ratio. Several people's in my core tried talking me In to the close ratio but I love the wide. Magnum that is. I like stated above use 1st-5th and cruise 55-65 always in 5th. So every road but interstate I don't use 6th. But give me interstate and 6th is great cruising 65 -+++++ at low rpms. I got 4.11 rears. Car is down right a handful through 4th with 575 to tire and the 4.11s with wide ratio trans.
I used the tremec gear calculator to build my setup.

[Steel409]

Hey everyone,

Sincerest thanks to all of you for the responses to my post. This site never disappoints and it's people like you that help the hobby flourish.

After talking with SST, I decided on the T56 Magnum w/ .63 overdrive. They said I'd love the 1st gear ratio and I'm looking forward to 1st-5th for most driving and 6th for expressway cruising 75+ mph.

Here's my ride...

[Lonnies Performance]

Beautiful car... I miss my Nova all the time.

I think you will really like that trans with a 3.73's.
Even with 4.10's it was fine unless running 75+mph for extended periods, where less rpm would help reduce the engine/road noise.

[BA Barakus]

I have a TKX in my 69 Ford Falcon and love it. Didn't have to do anything going from the old 3-speed automatic to the TKX and it will hold more HP than the current 408 is capable of putting out. Great transmission!

[Steel409]

Beautiful car... I miss my Nova all the time.

I think you will really like that trans with a 3.73's.
Even with 4.10's it was fine unless running 75+mph for extended periods, where less rpm would help reduce the engine/road noise.

Thank you!