I run the TKO 600 behind a warm 496 wedge. Street and road course. I have been happy with it... cross country and on the road course.

With this transmission, you have a choice of OD ratio. ~.81 or ~.65. On my setup, .81 makes a perfect top speed gear and .65 a perfect fast cruising gear. I went with .81.

A 6 speed reduces the trade-off... you can have both a top speed gear and fast cruising gear.

There is also strength to consider. After freshen and tune-up my torque is pretty well maxed out for the TKO600. Any more and I would need something stronger.

The TKO's are 5 spd, the T56/T56 Magnum is a 6 spd, double OD

Agreed, the .64 OD is often my recommendation for customers I do installs for, and my personal toys as well, as I like rear gearing in the 3.90- 4.50 range, the .64 OD responds well at highway cruising speeds and offers a comfortable RPM range for the engine, esp if outfitted with multiple carbs, and the MPG increase is often mind boggling, on cross country jaunts, HotRod Power Tours. etc I could muster up to 20-22 MPG cruising at 70-80 MPH with a 450 HP 440/6 pack and 4:10 gears, including a 472 HEMI running a TKO .64 OD and 4"10's could pull down 15-16 MPG on the events/runs, as long as you weren't tempted to put your foot into it

I would choose between the 4sp OD gear set or T56 Magnum. The TKOs are not worth cutting the car up.

Silver Sport 6sp kit is nice but after you add bell, hyd setup and clutch to the base kit you are over $6k.
Passon gear set is $2K if you have a 4sp car.
So is a modern designed trans with 2 extra gears worth $4k more?

Worth 4K more?
Depends on how long you are going to own the car.

After driving my 2010 Challenger with 3.91 gears and a 6-speed 12hrs I think it's worth pulling my Hemi 4-speed from the RR and doing the T56 Magnum swap.

I put a Passon OD gear set in my car. Doing the math,"4th" gear puts the 3.54 dana right at 2.8. It does a very comfortable 75mph at 2700 rpm. It made my car much more of a pleasure to drive on the interstate.

How's the RPM drop between shifts... do you have much of a cam?

Your going to cut the floor with either a TKO or T56 regardless if you want it to fit/clearance correctly, and achieve YOUR desired/needed driveline angle, for some the trade off of cutting the floor is no issuse, for those that have issues with cutting the floor there's other alternatives...

but for those that have a build that's going to see some stout rear gearing, a deep OD 5 spd or double OD 6th gear is the only way to go...

As to your question: "So is a modern designed trans with 2 extra gears worth $4K more", look at it this way, if I told you I could add 250+ hp to your current engine build for $4K more you'd be looking to round up some cash, same as if I told you your .80 gear set 4spd OD for $2K running a 28" tire and 4:10 gearing will be turning 2500 RPM at 70 mph or 5000 RPM at 130mph, you might be OK with that?, but if I told you for $4K more that same tire/rear gear set with a T56 .50 OD can still turn 2500 RPM but your cruise speed is now 110 MPH, and at 5000 RPM you have a 205 MPH capability, I think you would be inclined to spend the extra $4K, unless you don't like going fast?

Rpm drop between gears "feels right", unlike the factory pick up overdrive I ran before, maybe because of the lack of a granny first gear?
Hemi box to Passon OD box ratio comparison:
1st H 2.65 : 1,
POD 2.66 : 1
2nd H 1.93 : 1,
POD 1.59 : 1
3rd H 1.39 : 1,
POD 1.00 : 1
4th H 1.00 : 1,
POD .80 : 1

As for camshaft, I tried to source one slightly larger than a factory sixpack cam:

INT .470" EXH .504"
214 223
112

jess

Cutting the floor is no biggie but cutting the torsion bar cross- member is a bit more involved. I would not cut my cross-member for a TKO but a T56 magnum might be worth it.

I like how Silver Sport replaces the upper hoop with a newly designed cross-member. A chassis guy suggested that to me a couple years ago instead of raising the hoop like most do. Not sure which is the better approach.

For a B/E body TKO install you don't cut into the torsion bar crossmember, for A body yes, the upper tunnel loop is too small

the T56/56M you'll need to cut out the upper loop/hoop, and trim out some of the lower torsion bar brace to fit the new upper loop/hoop in, but the torsion bars/area remain intact

To me the biggest shame in the hobby is that Passon missed the boat with his 5 speed by a few years.
Had that transmission been available in quantities where you could have just picked up the phone and had it in a week they would have sold thousands of them.
Every other option is far from perfect...but they are readily available.

68 Charger, 440 with 484 cam, 4.10's and the Keisler 5spd. It was a pain to get right in the car and the thing shifts clunkier than a Getrag hooked to a cummins. It's also too much OD for the cam. In retrospect I really wish we had just put a Passion 4spdOD in it.

Sounds like you may have one of the earlier Keisler kits, you really need to remove some of the webbing on the transmission case that interferes with the floor crossmember, use a 4 spd hump, to get the transmission up into the tunnel to correct the driveline angle, and if you have a first generation shift tower, you need to upgrade to a 3rd gen tower for better shifting

I run a Keisler TKO 5spd .64 OD behind my 70 Charger 440 6 pack/450 HP, Dana 60 4:10, 27" tire, cam is a .470 with 1:6 rocker so in essence it's .520 lift and pulls fine in all gears, OD cruise RPM's are ideal for my set up, could be your cams duration that's killing your OD RPM's, one of the reasons I went with a smaller cam for shorter duration, but increased the lift with 1.6 ratio rockers

lift of the camshaft has nothing to do with lower rpm drivability, it is the duration & overlap that can make or break the cam choice with High gears & OD, my cam is a solid flat tappet 248 @ .050 in a 512 cid, it works great in my 68 Charger with 3.54 gear & .69 OD.

Anyone run the Passon 4 speed overdrive at the drag strip?

I'm sure the 18 spline overdrive gear set is more than strong enough but how much RPM drop is there shifting through 1st, 2nd and 3rd gear when the car is really run hard?

Is it a major performance loss?

Any idea how much ET is lost with the Passon 4 speed overdrive setup compared to a regular Hemi 4 speed?

Agreed, well aware of that, I mentioned the "lift" of cam that I chose as being the determing factor of the duration I desired, I achieved the lift value I wanted by going with 1:6 rockers, this was to avoid having a cam made to spec...I mentioned above several causes for the poster to help determine his ills with his TKO set up...duration was one of them, as the poster released no information to help in that aspect

Thank You

The kit was bought in 2008 or 2009, so maybe 'older'? And yes, the lumpy purple shaft is a poor choice but for doing what my dad wanted - that sound. The engine is happier in 4th @ 60mph than it is in 5th, really need to be going 70mph for it to be happy up in 5th, and it's really happy @ 80mph, which is fine when the commuting traffic is actually moving.

What's this shift tower swap? I hate the way this thing operates currently, I can almost never get it to go into 3rd with any kind of gusto (far away from power shifting).

In 2001 I helped a friend install one of the first Keisler TKOs in a 1970 440+6 RR. It was so early that they sent him a prototype pistol grip shifter to use. He drove it to the Nats and we exchanged it for one of their newly finished shift handles.

The car really dove nicely and the 3.54 gears seemed to want speeds above 70 when in OD. MPG dropped at 60-65 mph.

If you have a first generation shift tower it will be gold cad plated, the 2nd/3rd Gen towers were red/blue anodized, the fist gen towers were real crappy, no spring support, loose tolerances, ratchety shifting and often the shifter experienced "buzzsaw" vibration at various RPM's...As far as the 2-3 shift you can't force that, shifting a Tremec isn't like shifting a 833 4spd, you need to learn just how much you can get away with rowing the gears

Keisler is now owned by Silver Sport Transmissions, but the product is pretty much the same but with newer refinements and offerings, I'd talk to them to see if their shift tower is compatible, which I sure it still is, or appears to be...

if you do swap out the tower, it's just 2 Allen bolts, make sure the transmission is in neutral, unbolt the tower, bolt in the replacement, make sure the machined flat where the shifter handle bolts on is facing the driver's side when installed


Bottom pic is with shift tower removed, this is what the shift forks inside should look like in orientation when the tranny is in NEUTRAL position

Mike