KB - T56 Upgrades (Conundrum)

[scramblr]

My next two upgrades are a KB Mammoth and a T56. It was going to be in that order, but my rear main is leaking (just had it "fixed" in Aug 2019). So I think I have to rearrange my priorities as I don't want to pay to have the tranny dropped twice. Figured do the tranny upgrade now, fix the rear main and do the KB down the road.

Lethal has a good price for the entire T56 kit. My Spec 3+ and flywheel have less than 500 miles and Spec Tech Support stated I can just upgrade the disc to a 26 spline. I've read of other people doing this. Saves 50% on a clutch swap or a lot more if going with a different clutch, e.g., McLeod RTX.

So for the gearing...I have 4.10s and no traction but I love them. Traction issues are going to get worse with the KB. Should I go with 2.97 or 2.66 and swap 3.73s in? Or any other advise is appreciated. I have 3.73s on the shelf so no expense on those parts. I run 28" tires.


https://www.lethalperformance.com/l...ansmission-swap-kit-2005-2014-mustang-gt.html

 

[Midlife Crises]

I am running the 2.66 first with a 4.30 final and I can tell you first gear is very short. I am thinking of giving 4.10s a try.

 

[Silver'nStripes]

I had been running the 2.66 gear set with 4.10s, 28 inch tall tires. The car was a bit of a dog off of the line, though I think the sintered iron clutch I'm running complicated that a bit. The closer ratios of the 2.66 gear set is nice for keeping the rpm up during a run, but you need a lot of rear gear to have a good starting line ratio.

Just swapped to 4.88s, which may have been a little too much gear, but I knocked quite a bit off my best ET. Again, I think the sintered iron clutch disc is going to benefit from a bunch of rear gear.

Don't know how much you street drive the car, but 4.10s was a good rear gear for cruising. I should add I have the .50 6th gear with the 2.66 1st (2.66 1.78 1.30 1.00 .74 .50). The engine would lug a bit on big hills, but on the highway I could cruise at 80 all day long. Now it's more like 65 lol.

A word of warning about the Kenne Bell, you will absolutely battle high IATs that will pull timing and slow you down, regardless of weather. The whole intercooler system is a joke. Most everything can be upgraded except the design of the heat exchanger core in the intake manifold. It necks down to a 3/8" ID fitting with a bunch of 90 degree turns, not good for water flow. Unfortunately I figured this all out long after it made financial sense to make a change.

https://www.s197forum.com/threads/anyone-disassemble-a-kb-intercooler.136387/#post-2451888

 

[scramblr]

Kind of talking myself out of the tranny right now and just fixing the rear main. I really want the s/c first. All about wants. Car is not a DD and mainly street driven although hoping to get back to the track in the future. Looks like 2.66 with 4.10s is a good trade off between street and track. Can always change gears around.

@Silver'nStripes - Yours is one of the many KB threads I have bookmarked. Fully aware of what I'm getting into, but the p/d twin screw choices are down to one unless you take the DOB route which I'm not. The Saleen is pretty much maxed...I need/want bigger and will just deal with the IATs like you guys have.

 

[MrBhp]

I've the same conundrum. Neither t-56 has the perfect gearing for my likes. 2.66 is way too long for 1st. The other isn't much better. I can keep the 4.10 gears out back, but I gain nothing with the t56 final drive. I would like to spin a bit slower at highway speed.
@Silver'nStripes I only see options for .62 and. 63 6th gear. I was sure I had looked at one with the .50 6th. Maybe it was 6060. ??

 

[DBcooper]

I also have 4.10 and am eyeing a magnum xl. I’ve asked about 15 vendors which gear ratio to go with and 2.66 was the overwhelming majority. 2.66 will keep you up in the rpm range a little better after shifts.

 

[Badd GT]

I have 2.97 w/3.73 and have been considering going to 3.90 or 4.10 to be a little more snappy off the line. Second the cooling issues w/ KB. Out of curiosity, why the anti DOB?

 

[Pentalab]

Don't know how much you street drive the car, but 4.10s was a good rear gear for cruising. I should add I have the .50 6th gear with the 2.66 1st (2.66 1.78 1.30 1.00 .74 .50). The engine would lug a bit on big hills, but on the highway I could cruise at 80 all day long. Now it's more like 65 lol.

Lemme get this straight. The T56 has TWO overdrive gears ? So it's really a 4 speed tranny...with 2 x overdrives ? Every time I look at various manual and auto transmission ratio's, it always appears the gears are always in the wrong place. It appears the only...'fix' is to tweak the rear end gear ratio, to try and optimize the entire mess.... and / or tweak the rear tire diameter.

 

[Silver'nStripes]

@Silver'nStripes - Yours is one of the many KB threads I have bookmarked. Fully aware of what I'm getting into, but the p/d twin screw choices are down to one unless you take the DOB route which I'm not. The Saleen is pretty much maxed...I need/want bigger and will just deal with the IATs like you guys have.

Glad I could be of some assistance! The KB is a fun street combo for sure, it's just frustrating when you're trying to run your best at the strip.

FWIW I just finished a tune with Lito, he is not a fan of the KB stuff either. Along with the high IATs he strongly disliked the ridiculously large throttle body and bypass valve location. All workable stuff, but less than ideal. If money was no object and I could do it all over again I've gotta think I'd do a DOB setup with a big ol' VMP supercharger. It's not cheap though...

@Silver'nStripes I only see options for .62 and. 63 6th gear. I was sure I had looked at one with the .50 6th. Maybe it was 6060. ??

Take a look at part number TUKT12019.
https://www.tremec.com/menu.php?m=105

It appears the only...'fix' is to tweak the rear end gear ratio, to try and optimize the entire mess.... and / or tweak the rear tire diameter.

Yep, that's how I landed on the 4.88s. Launching at 5k, shifting at 7k, rev limiter at 7500, and probably using 5th gear in the quarter. All while crossing my fingers that the Eagle rotating assembly stays in it LOL.

 

[scramblr]

Glad I could be of some assistance! The KB is a fun street combo for sure, it's just frustrating when you're trying to run your best at the strip.

FWIW I just finished a tune with Lito, he is not a fan of the KB stuff either. Along with the high IATs he strongly disliked the ridiculously large throttle body and bypass valve location. All workable stuff, but less than ideal. If money was no object and I could do it all over again I've gotta think I'd do a DOB setup with a big ol' VMP supercharger. It's not cheap though...

Yeah, not many people around here are fans of KB, and in some cases for good reason when trying to squeeze every HP out of a system which I'm not. I don't want to piece a system together and it isn't any cheaper...actually I've priced out what I would do and it comes out way higher than a KB kit for the same RWHP. Would've probably gone with Whipple but they stopped manufacturing for our motors. Glad to hear Lito worked through it as he's the one I would contact to do the tune.

 

[Midlife Crises]

When I was digging around for T56 Mag parts I found there was at least three gear sets available for that transmission. Looking at what was used by GM, Mopar and Ford in their version of the T56 Magnum also turns up different synchro designs and overdrive sets, some of which can be interchanged without much trouble. The double overdrive is in the tailhousing and can be changed. I upgraded synchros and shifter fork pads when I did some repairs to an XL.
I thought messing with gear ratios, tire height and RPM was all part of the game!

 

[DieHarder]

Yeah, not many people around here are fans of KB, and in some cases for good reason when trying to squeeze every HP out of a system which I'm not. I don't want to piece a system together and it isn't any cheaper...actually I've priced out what I would do and it comes out way higher than a KB kit for the same RWHP. Would've probably gone with Whipple but they stopped manufacturing for our motors. Glad to hear Lito worked through it as he's the one I would contact to do the tune.

The old adage comes to mind "Pay me now or Pay me later." Depending on your budget IMHO the least expensive option would be to piece together a DOB setup starting with the intake manifold and what parts you can afford now and upgrade later. The installation instructions are available online so you can see exactly what's needed and how to do it including all wiring. I ended up getting a complete kit and after doing the installation myself found it fairly simple and I'm just a shade tree mechanic at best so anyone with a modicum of knowledge/experience will be able to take that information and figure out how to cut some corners on upgrades they'd like to make for more horsepower, cooler running or better efficiency/reliability.

What I wouldn't do is settle for a system that has known/fatal weaknesses going in and are impossible to work around (especially heat issues in hot environments) because you're quickly going to find the limits and wished you'd done it right the first time. In my case I started with a stock motor and found a slightly used M122 which has served my purposes well and been amazingly reliable. Eventually either I'll build the motor and upgrade to a VMP or sell. Not sure which but I can guarantee if I sell the new owner will be thrilled with what I've built or I won't sell (not that I really will ever want to; truth be known having too much fun).

If you're patient, every so often DOB has sales on upgraded manifolds/superchargers and other parts so that's also an avenue to a DOB. Besides, Lito loves to tune them. Got mine done in just 3 rounds; 1 idle and 2 tunes later have never looked back and rock-solid reliable for over 3 years now.

 

[Juice]

Lemme get this straight. The T56 has TWO overdrive gears ? So it's really a 4 speed tranny...with 2 x overdrives ? Every time I look at various manual and auto transmission ratio's, it always appears the gears are always in the wrong place. It appears the only...'fix' is to tweak the rear end gear ratio, to try and optimize the entire mess.... and / or tweak the rear tire diameter.

Yup.
I would love to have the mt82 ratios in the magnum xl case. But I do love the one piece 'old school' driveshaft, and the trans mounted shifter.

 

[Aussie-Parnelli]

I run a T56 in my '06 converted to a Pfitzner PPG Dog Box about 6 years ago it has a 1st gear 2.437 6th gear .77 also run 4.1 rear gears
Current horsepower at engine 746hp but recently done some more mods and having dyno done on Wednesday
Just love the extremely fast shifting of the PPG gears on the track but not really pleasant for street use with lack of synchros
I run the Saleen series 6.5 supercharger 8 rib 2.7 pulley and 18% overdrive with the Extreme intercooler with fans and never had extremely high IAT's
Also have Nitrous Express system 100 shot
The gearbox I used came from an 2006 Australian Falcon GT which has an internal shifter mounting a long extension housing and a 31 spline output shaft which allowed me to run a standard slip yoke one piece tail shaft 1330 uni joints with a normal U bolt connection to pinion. The shifter lined up perfectly with the standard shifter floor opening