TKX maybe
 

I've been thinking about swapping in the tkx from the original m21 I have in my 70 gto. The 2.87 first gear and the overdrive sound real appealing. I'd keep all the factory clutch linkage and bellhousing. Firsr off all I'd like to know if one of the vendors has a shifter handle that looks the same as the original Hurst competition plus shifter(roundish) and of course comes up through the floor in the stock location. Second is I have 3.31 gears with a 255/60-15 rear tire which is around 26.5 " tall. My car runs around 2800 rpms at around 65-70 mph. The .81 OD drops it around 500 rpms which to me sounds ok. The .68 looks like it would drop it additional 200 rpms more. I think I'd be more inclined to go with the .81 OD but not positive. Motor is the original 455 with a ra4 sized cam. Thanks for any opinions.

One part I'm pretty sure wouldn't work anymore would be how now you put it in reverse and turn the ignition key off and it locks the shifter so you can pull it out of gear unless you have the key on. The original anti theft device...lol.

Yes, they do make round bar handles that look stock. In fact, if you have a Comp Plus round bar handle already, you can simply unbolt that and bolt it directly to a TKX shifter. They use the same sticks and interchange.

It's the shifter itself you'll want to buy with the correct offsets to work properly with your car to come up in the floor in the correct location. They make various offsets depending on which brand you go with.


Yes the back drive linkage will no longer be functional with a TKX. What I do is keep that in the locked position so the steering column won't move and you can remove your key. For the back up lights you'll just jump a couple wires off the switch on the column and run them down to the switch on the side of the transmission. Tremec sells a small weather sealed plug for that connector on the side of the trans to make it simple, or you can make your own.

On the gear stuff, I've posted about that many times and have been pretty set on the .68 overdrive deal. Especially now that Tremec has decided to raise it to .68 instead of the previous .64 In my opinion that was a mistake as I now don't like running as much rear gear as I once did with it. The whole idea with an overdrive is to get the highway cruise rpm down, not up. I mean you'll be investing $4000+ so lets take advantage of what it has to offer. I don't even look at the .80 overdrive deal and have never sold/installed one for anybody either. Quite simply if that's all the overdrive you want, you're pretty close at this point of just making a small rear gear change or maybe tire height adjustment to get the same result at far much less cost $$$ But you hurt the other end of the spectrum. 5 speeds cure both ends, but take advantage of what it has to offer.

What you really gain with the swap is the 2.87 first gear, and the overdrive to boot. Drivability on both ends is improved.

If you're worried about the 3.31's and a .68 overdrive, I wouldn't be.

I run the same 255/60-15's on the back of our camaro and use a TKO .64 overdrive in that one. I'm just running 3.55's out back, and even with the little 302 it's perfectly fine cruising as low as 35 mph in 5th. A big 455 Pontiac will have no issue at all pulling your car around with the 3.31's , especially since the new TKX is now .68 overdrive. In fact with that small overdrive change it comes out almost exactly the same as our Camaro. So in your case, in overdrive it's essentially like cruising in 5th with 3.55's now that they have raised the 5th gear ratio. Not anything I would be concerned with in your case.

I have the TKX with 2.87 1st/.81 OD. 467 cid, 3.31 rear, 27 inch tire.

I totally respect FJs comments and I'm sure you would not go wrong with his advice. But, I think it depends on how you drive the car. If you do a fair amount of driving, cruising at 75 or more, then the .68 OD is probably a good idea. If you rarely cruise that fast for prolonged periods then the .81 would be as good or dare I say a little better. The roads I drive on are 55 mph roads. At 65 mph I'm at like 2100 RPM and I can do that all day long. 75 mph is around 2500 and is still very comfortable. I think if I had the .68 OD I would use it less, but maybe I'm wrong. But, I'm very happy with my overall gearing.

You could also do the 3.27 1st/.72 OD. But even with the 2.87 1st, traction is an issue so I'm not sure how the 3.27 would do.

Do it and don't look back. No point having a weak 4 speed with no OD anymore these days.

Makes the car so much more fun.

Plus with the new TKX you don't have to cut your floor. So every reason to do this swap today.

This is my view as well. Unless you're concerned with utmost originality, put the Muncie underneath the work bench and bolt in a TKX.

I have the TKO with 2.87 first/.64 OD, with 3.89 rear and 255 60 15 tires. First gear is a bit much and someday I plan a change maybe to a 3.50 rear. The .64 OD is perfect with the current rear gear though cruising 70 mph at about 2200 rpm

I assume you've seen this new TKX in the sales section? It has the it is the 2.87/.81 combo: http://forums.maxperformanceinc.com/...d.php?t=866159

Another way to look at this is to compare what your equivalent ratios would be between the M21 and the TKX. With your M21's 2.2 1st, the 2.87 TKX would be like having a 4.32 rear with the M21 (or like a M20 with a 3.77 rear). The TKX in OD (.81) would be like a M21 with a 2.68 rear. 2.68 is a pretty respectable highway gear. But again, if you're cruising for long periods at > 75 mph then maybe the .68 which would be like a 2.25 rear in the M21.

How much power are these TKX transmissions good to ?

600 ft lbs stock. They can be modded for more.

I have 3.31s with the .68 OD in y 69 bird with a mild 455.Tom

To Scarebirds comment, when doing this swap, do yourself a big favor and just have a nice beefy custom driveshaft built so you don't have to worry about critical speed and such. Also with a trans capable of the abuse these things will take, you really should have a driveshaft capable of the same abuse anyway.

In every swap I do I have the driveline shop up the street build me a custom driveshaft that's good for anywhere between 600hp and 1000hp, usually with 1350 joints.

Most of my highway driving has a speed limit of 60 which means I drive at around 65 mostly. Only occasionally do I go on I95 which is a limit of 70. Before my post I went on the wallace site and plugged in a bunch of different senarios but I wanted to hear what real world experiences were from you guys. Didnt want the car running like a high idle at 60-65 mph,,,I dont mind some rpm ,,,2800 cruising is just a bit much for me. Also the 2.87 VS 2.20 with my 3.31 gears sounded like a nice change for taking off whether its a hard or easy take off. With the iron exhaust manifolds it dynoed 480ish hp and 560 trq. Headers it was a little over 490 hp and 570 trq. I do play at the 1/8th mile now and then on bfg t/a street tires and the 2,20 1st gear sucks.

Yes I would definitely have a custom driveshaft done and not cut up my original. Also my original shifter was mentioned. On mine the chrome handle isnt a simple bolt on. and the rear gear ratio and back tire size are not going to change.

How do you like the .68? If you changed it which way would you go? Im assuming you dont run a short tire?

We do a lot of driving with ours on 65 mph roads, which is only 1800 rpm (.64 overdrive, 3.55's, and 27" tire) and the 302 is fine with it. 70 mph is roughly 2000 rpm if I want to squeak a little more in a 65 zone. On the major highways it's 75mph here and I can easily float along at 2200-2300 going 75-80mph but the best part is that it will knock down just over 21 mpg whether I'm doing 65 or 80, it doesn't really care. What many also forget is how quiet the car is now that the engine isn't buzzing 3000 rpm down the freeway. The lower you keep the rpm the quieter the car is. I even find myself using 5th gear in the 35-45 mph zones all the time.

Your 455 makes a ton of grunt and should not have a single issue lugging your car around at lower rpm, even below those highway speeds.
No worries on the chrome handle if it's the factory push in Hurst style. They do reproduce the round bar handles that bolt on to the aftermarket Hurst and Tremec shifters. I run one in the Z since the original Hurst shifter has that push in handle and I didn't want to modify that, those original sticks with the specific Hurst part number on them bring some serious coin. Plus I wanted to save all that with the Muncie and driveshaft as a package deal since it's born with that car.

Here is my opinion on these O/D transmissions. You need to take into consideration your Driving style, Speed limits, Engine rpm which I think is the most important, Rear gear, and Tire size. Where is most of your driving gonna be, on the highway or around your City or Town. I guess if you want the best of both worlds you could move up to the T56 with 6 speed and two O/D's.
I was gonna go with the .72 O/D but that first gear ratio of 3.27 was no good for my setup. A good Friend of mine that is much better than myself with numbers talked me out of it. and he was right. I'm very happy with my current setup.

Anyhow, point is that one size doesn't fit all. Find yourself a rpm,tire calculator online and go from there.

https://purperformance.com/p-29669-rpm-calculator.html

I'm running the new TKX with .81 O/D, 275/60R/15 tire, and 3.73 rear gears. My engine like to cruise at around 2200 rpm. The after market shifter I went with is from Modern Driveline. It uses bellville washers for centering the shifter which I'm very impressed with. https://www.moderndriveline.com/shop...y-rear-socket/

Chuckie- what first gear in your TKX?

Wow that's only 60 mph....yikes You'd still have to buzz 2700 rpm just to do 75 mph.

It has the 2.87 first gear

Most of my " normal" driving is around town,55 mph and 65 mph. The 2.87 first gear is appealing to me as much as having the overdrive. I will admit I'm not much of a putt putt. The car has its original drivetrain but I put it through its paces. Have been since 1986.

If we had the interstates like you guys have I would have a T56 installed. I can cruise at 70 mph no issues. And even 80. But that just gets a guy tickets here. Lol. The fastest speed limit here is 110 klms. Like 68 mph. My car would be no good with a .64 od at that speed.

Just my opinion, but you really need to drive your current setup and find where your engine or combo starts to lug the engine. This will be a starting point of what you'll be comfortable with. After that it will be rear gear change or tire sizes to match up. I was gonna do the .72 O/D, but at 60 mph I'd be at 1900rpm which is not good. My engine starts to lug at around 2000 to 2100 rpm. I can always go back to 3.23 or 3.42 gear if I want more cruising time. So with 3.23 gear at 80 mph would put me at 2500 rpm. but that's not how I want my car to run.

So just for example 60 mph 28" tire 3.23 gear .64 od I'd be at 1500 rpm. My setup would need to go 90 mph just to see 2200 rpm. This is what my friend pointed out to me with the .72 I'd have to drive at 70 mph to keep engine happy.

You'll enjoy the increase in first gear. Much more pleasurable to drive around town. That's the benefit of these overdrives. Not only getting a comfy cruising rpm but you also help out the other end of the spectrum at the same time. You get the best of both.

55-65 won't be a problem with your setup in 5th gear with the .68 but if you really don't want to putt-putt then just don't use it at lower speeds if you'd rather hear the engine spinning.

Me personally, 65 mph with this deal is 1800 rpm (3.31/.68/27" tire), I wouldn't consider that putt-putt, that's just nice comfy cruising, no engine noise, and should return exceptional mileage too. Once you get used to the idea of having a muscle car that actually cruises like a new car in overdrive you'll find yourself using it more and more.

It's hard for people to get used to that idea after decades of driving them without an overdrive, they either feel the engine still needs to be spinning higher rpm or they just have an engine that requires some more fine tuning to make it happier at those lower cruise speeds.

You can look at it this way, how slow do you go in 4th gear putting around before you think you need to drop down to 3rd gear? At what rpm do you bring the engine down to before you feel like it's struggling? Well 5th gear will act the same way.

From my experience driving 4 speeds for decades, a typical well tuned muscle car can drive around in 4th gear in 25-35 zones no problem at very low rpm.
Your setup with 3.31's and a 27" tire does 35 mph at 1500 rpm. That should not be an issue at all. Or maybe you like just leaving it in 3rd gear?? The overdrive just gives you another option ;)

But at those speeds you're buzzing 2700-2800 rpm, not really helping the MPG or the wear and tear like that. You're pretty much stuck at your 60 mph goal and 2200 rpm.

We have a variety of interstates here that range from 55 to 75 mph. I can use a .64 5th gear on all of them, and even climb the mountain in 5th gear.

There would be no reason at all a .64 wouldn't work in your combo, especially the new .68 since .64's are no longer available anyway.

With your 3.73's and a 28" tire and the .68 overdrive you're only doing 2000 rpm to go 65 mph. If that's the speed you want, 2000 rpm is easily doable for a big pontiac engine. If you have an engine that struggles at those lower rpms then something in the engine setup needs to be revisited.

With a problem like that, you wouldn't even be able to use 4th gear in a 4 speed below 45 mph and that just sounds crazy. I don't know of any muscle car that can't use a 1:1 gear below 45 mph that has 3.73's out back.

Got any driving videos??

Respectfully, I don't really care about MPG. lol At this point in my life I'm just glad I can go to the pumps and get gasoline. With the way the world is I figure governments will find a way to push us out of the hobby. I'm not sure what I have for videos. I'll look into it.
You have some valuable points and maybe my engine just needs more tuning. I don't know. It runs so nice and performs so beautiful I leave it along. Just the maintenance each year. I have KRE heads on it with Dave's road paver. 245/252 I think. It made close to 600 hp on the dyno. 32 deg. I am running a vacuum advance on it. Next time I'm out I will disconnect it see how it acts. It doesn't like 2000 rpm. In O/D it starts to lug in lower rpm. It is a blast to drive for what I'm doing.

Really that's all that matters if you're enjoying it as is.

We daily drive ours so MPG is part of the equation. So I tune and tweak things, even on the cars without overdrives, to make them at least somewhat respectable on MPG. It's kind of funny at the pumps, once in a while I'll get the MPG question from someone and they are shocked that these 50 year old cars are doing better than their new SUV's. And that's one of the biggest reasons I look at overdrives. The other is keeping the wear and tear to a minimum, as we know it's not cheap to build these engines anymore either, let alone operate them on a daily basis.

Yeah mine is not a daily driver. I take it out when I'm in the mood or have a minute. I actually googled the tkx thing and found some other forum opinions...found some were asking about tkx overdrive in the same configuration as mine ,gears,tires,etc......68 vs .81.....opinions were down the middle 50/50 also. Like was said either one is fine...try to figure out your expectations I guess.

These two calculators may help you decide which way to go. It certainly helped me decide that the 3.27 TKX was right for me.

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

https://weddleindustries.com/gear-calculator

Yeah you'll get that basically because you have 2 groups of people. Those that struggle to get an engine to run at lower rpm efficiently and those that can.
So you end up with 2 different opinions on overdrive ratios.
Been that way since these swaps became popular 30 years ago.

Usually when I do these swaps I'm also digging into the carb and distributor to tweak and make the engine a little smoother at lower engine speeds.

It's also where electronic control lock up converters have a big advantage in auto overdrives compared to the TV cable mechanical stuff. Not only can I dial in the converter lock precisely but making the engine happier allows me to keep it locked longer.
The only difference here is your left foot is your lock up converter :)

My 7040267 carb has no port for vac advance. Talked to cliff,,he has added the nipples before on these carbs.

I don't know but I think there's a reason why there are 3 other gears between 1st and 5th. You're supposed to use them. I never liked lugging a motor. I suppose it depends on the motor too. Low compression, small cam motors may tolerate that better.

^^^^ Ahhh, That's what I'm alluding too.

Changing the topic a bit, What fluid are you guys running in these TKX transmissions? I ran GM synchromesh in my TKO-600, and I ran the Dexron III in the TKX for awhile then switched back to the GM Synchromesh fluid.

High compression, 254 @ .050 cam and small 302

https://youtu.be/e39e6p7NMY0

I use Amsoil Synchromesh in mine. My sons from G-force they recommended 2 quarts of 85-140 gear oil and a quart of synthetic ATF mixed in.

Thought that was a bit on the odd side but it shifts beautifully.

68 mild 400, 3.55 with close ratio .68 OD TKX with SST shifter mod and 26” tires.
No regrets.
Game changer

Go .68 OD. If you're concerned with lugging the engine, drive faster before you shift, or just stay in 4th (No different from what you have now) longer. Then you have the extra OD for those times that you need to cruise on the interstate.

If you get the .81, juggling shift points will be of little benefit if you ever need the extra OD.

Recap - with the .68 you can always delay the shift into 5th.

Sent from my SM-T817V using Tapatalk

Nicely done video. But in all fairness, you're not really putting much load on it when you're down low in RPM and trying to come out of it. You're easing into the throttle very gently. I don't really chug around like that so I just downshift. :)

He doesn't cruise on the interstate. Did you actually read the post from the start.? Did you watch Formulajones video. Most of us don't drive like that..!!!



Here is his post. ( O/P)


(Most of my " normal" driving is around town,55 mph and 65 mph. The 2.87 first gear is appealing to me as much as having the overdrive. I will admit I'm not much of a putt putt. The car has its original drivetrain but I put it through its paces. Have been since 1986.)

This is me too, I drive the car. Hammer it.

Gears are for shifting. That is the most fun part with a standard. Can you say Grampa. lol. I know I shouldn't post this but that's the way I feel. That driving is so boring.

https://www.youtube.com/watch?v=gtHulbSZOnw

https://www.youtube.com/watch?v=4-YULu5wT18 10.32 at 132 mph

Hammering on the car all the time isn't a normal thing. We do drive these things daily after all. We have to drive civilized most of the time and that video shows that even a big cam in a small engine doesn't need to be downshifted all the time. That's the whole point of the video. If 455's can't do that then the engine either has issues or you guys are telling me a high strung 302 does it better.

I am actually putting a load on it. That's about 1/4 throttle in high gear at very low speed and it picks up speed very well with no need to downshift. You can actually mat it if you want, it just makes 4 barrel sounds and accelerates, but it's honestly just a waste of gas and unnecessary load when your putting around 35 mph zones.
Probably would have shown better what the engine was doing if I put a vacuum gauge up there.

The real point is a 254@ .050 cam in a 302 that has a reputation for being so high strung has no problem with a .64 5th gear and 3.55's out back. If that engine does it then most any other engine shouldn't have an issue

Actually most do drive somewhat civilized on public roads but you are missing the whole point of that video if you think I should be hammering on it.
I have other videos showing that if that's what you want to see. There is a time and a place for that.

How do you treat your daily driver? Hammer on it all the time? Just cause I daily drive a muscle car doesn't mean I should be racing at every stop light. Treat your daily like that every day and it likely won't last very long

That's a sweet running car!

This entire thread is why these kind of decisions are very individual and specific to the owners desires, needs an usage. There is no one-size-fits-all solution. That's what also makes it fun and interesting. Your car is your car. Each if us has to be honest with ourselves about the car we have and how we use it. To pick your setup based on someone else's use that's different than yours, will probably be a mistake.

For me, I always try to keep my car in a gear where I have responsive acceleration if I want or need it, without a shift. That's just me.

And to FJ, I'm not disparaging or criticizing you. You are an awesome dude. You have more car knowledge than I ever will and your contributions on the forum are epic. You've got your stuff setup the way you want it and that's fantastic. We just may disagree on this one a bit. :beerchug:

Nothing wrong with that. That's what makes these threads great. I agree, and have the option of buzzing around in a lower gear if I want to, maybe when I'm feeling a little spunky. Pick which one ya want and have some fun, but I also have the option to just let the engine mosey along, sip fuel, and be just about completely quiet. That's what that video is about.

Honestly a big engine is really good at doing that, should be better than that 302 actually.

Thanks,


And just for giggles, it does zing when ya want to. Here's a short video on a chassis dyno. Interestingly enough, it has a decently flat torque curve that hangs on quite a while and torque peak just about matches the HP peak. Contrary to what is common folklore with these engines.

https://youtu.be/jI2SxDxH8bM

Very nice - must be fun to drive!

The wallace calculator says right now I turn 2730 rpms at 65 mph. With a .81 it would be 2200 rpms and with .68 it would be like 1850 rpms. At 75 mph its 2550 with .81 and 2140 rpms with .68. Either OD would be a nice improvement over what I have now. I guess something to think about.

The Tremec calculator may be useful, it lets you see each gear and switch between multiple transmission options