For those that have installed the TKX 5 speed transmission I’m looking for feedback on any issues you’ve had or have with the transmission and if you would have done anything different. Installation process, any rattles/vibrations with the shifter? Other issues?

I have a 79 L82 with a BW T-10 4 speed, 3.70 gear. Engine mods include: 268 Comp Cam, Flat top Pistons, Edelbrock RPM Performer Heads, Roller Tip Rockers, Patriot Shorty Headers w/ dual exhaust. Current gears are 1st- 2.43 2nd- 1.61 3rd- 1.23 4th- 1.00. Tire height is 27”.

I’m looking to purchase the complete kit with the Close Ratio gears with 5th being 0.68.

Thanks in advance for your feedback.

 

I found that the force needed to move the Silversport TKX shifter side to side was more than I liked. However, their shifter tower has a set of centering springs than can be removed to reduce this force.
I modified my crossmember to make it removable, this makes trans install a breeze.
No shifter buzz with mine.
You're going to lose your ignition backdrive interlock gizmo, and TCS stuff if you care about that.
Silversport is big on centering the bellhousing, so be prepared to do that procedure.

 

I have a TKO 600 so not exactly the same. I love the transmission but the break in period was longer and worse than I expected. Once it broke in though, it shifts like butter.
I have a 427SB with 3.55 gears and the .68 overdrive. If I had it to do over, I might get the .82 (at least that's the other ratio for the 600 - not sure what the ratio is on the TKX.) The rpm drop from 4th to 5th is considerable. It's basically a four speed with a highway gear. You don't shift in and out of fifth. You wait until you're at highway speed, drop it in fifth and leave it there until the next town. Just a matter of what you want from your overdrive I guess.

 

Any chance you would consider a T56 Magnum 6 speed ? This is worth looking at.

 

I know the TKX is very popular here. And I considered it for my 69 big block. But just FYI.......I own a 2006 base model Corvette.....which has a T56 Tremec six speed transmission. Bought the car last August with 13,000 miles on it. Since then, I have had numerous driveline issues, including transmission issues. Rick at RKT Performance in Frederick Maryland runs a business that strictly works on later model Corvettes.....DRIVELINES ONLY. He knows his stuff and is a great guy, and a very very fair person. He offers an upgrade kit to the transmissions to replace the stupid and junk plastic parts in the shifter mechanisms with brass pieces. He showed me the plastic parts, and its just amazing Tremec would every install them. So.......with all this love for TKX........does it have the same junk plastic in the transmission? And if so....I question if its better than a good Autogear M23 4 speed. I know....it does not have an overdrive, ......but I am not interested in a Tremec transmission if its built like my 2006 transmission. I am not trying to hijack the OP thread here.....but I thought it was a relevant point / question.

 

From what I understand, the Tremec Magnum is not the same transmission as the T56 in a 17 year old C6. Nor is a brand new TKX, which has nearly the same gearing as a certain 4-speed, plus an overdrive, plus an internal shifter.

I'd love to give a review of my TKX, but it's still in the box thanks to scope creep. I ordered the same 0.68 OD, though. I think many here will agree that the SST bellhousing is a robust unit, but you'll need to make sure you zero the runout.

 

I would pick the close ratio version with the .81 overdrive for your setup. "1st gear x rear gear" should be close to ="10" so you would be at 2.87 x 3.7 = with the close ratio and the .81 OD. A very good match.

I have 3.07 rear and went with the wide ratio setup. The OD is definitely used for highway only for me with the 3.07 rear.

 

I have a 79 built L82 like yours with the 3.70 rear end. My initial install had a grinding in 3rd gear. Silver Sport sent an enclosed trailer to take it back to their shop in Knoxville. They couldn't determine what the problem was so they swapped in a new unit that has been flawless. Highly recommend Silver Sport. Only very small issue I have is it sometimes doesn't want to go in reverse.
It makes the car so much more enjoyable to drive on trips. 80 mph and 4000 rpm will wear you out.

Edit: I have the earlier TKO with the .68 overdrive.

 

They're not like the OEM versions. I put the original Tremec TKO in my '71 20 years ago. It's a street car that's also been on a road course and drag strips. Never had a single problem with it and it still works like new.

 

Based on all my reads about the six speed I would not consider it, not to mention the size of the T56. One of the advantages of the TKX is the size of the case, I shouldn't have to the do any mods to the tunnel or have to remove the engine to install it. Also, I do not want to cut the cross member for the installation. The TKX may be a PITA to install but could be installed without any mods.

 

Capt. Shark, since you also have the 3.70 gear the OD you selected is what I question. So far I have two responses in this thread, (yours) one with the 0.68 and (stingr69 w/3.07 gear) one with the 0.81. My calculations show in 5th at 2500 RPM my speed is 80 MPH with the 0.68 and 67 MPH with the 0.81. Seems the 0.68 is the better option but I only get to buy this once and there are no redo's on my budget. Would you keep the 0.68 or would you change to the 0.81, and 5th would be used on roads of 60 MPH or more, otherwise I'd probably stay in 4th.

 

Here's a spreadsheet I worked up when deciding which TKX to buy. The highlighted line is what is going in my wife's 79 with a 3.55 diff. The first line is what is currently in my 80 4-speed. I look forward to doing a side-by-side comparison by the end of the summer.

 

For comparison, you can look at what it would feel like with the old 4 speed and no overdrive.

.68 x 3.7 = 2.5 is what the effective rear axle ratio in 4th without an overdrive would be. Pretty darn low numerically. Doubt you could use 5th much but maybe a judgement call.

The .81 x 3.7 = 3.0 effective rear axle ratio in 4th without overdrive. I can say the L46 with a 3.0 axle ratio runs just fine at highway speeds. Did mine that way for years. 5th would get more use in this scenario for sure.

 

I would absolutely go with the .68 again. Your calculations are correct 80 mph is now 2500 rpm instead of a screaming 4000. And it only gets used on the highway.

One of the best mods I have done to my car.

And my understanding is the TKX has the same gear ratios as the TKO but is beefed up for higher hp engines.

 

Thanks to all that have responded. Once I complete this task, I'll provide some feedback, although due to being in the middle of summer I'll probably wait until Sept to begin the install process.

 

Bikespace posted a great spreadsheet on speeds and RPM's. But for those considering these overdrives, consider this. My 06 base model Corvette has 400 HP / 400 Ft Lbs torque. When I drive the car on the roads of PA,......I typically am at 55-60 mph. It has a 3.42 differential ratio. At 60 MPH.....in FIFTH gear the engine RPM is 1800 RPM. On level ground.....if I want to accelerate, and push gas pedal down.....it will accelerate, but with ANY incline up....even a shallow incline,......its is BOGGING. And that means that with enough gas pedal.....the car WILL accelerate,....but not quickly. If I want to accelerate quickly.....I have to downshift to 4th gear.

So point is......the FIFTH gear (and this is a SIX SPEED), is useless at speeds below 55 mph,....unless you like a bogging engine that is struggling....and this is a 400 ft lb torque engine.....imagine if you have less???. So, when I consider the idea of putting a TKX in the 69, and considering my driving style and speeds I can safely drive in Western PA......I don't really see a big advantage to a fifth gear. And if I did,....it would be the .81 overdrive, not the .68. It is important to know what RPM your engine develops the power / torque that allows it to instantly react to the gas pedal.....and on my 77, nor my 06, is it at 1700-1800 RPM......its bogging there. Not fun. So on level ground.....steady speed, I can shift into fifth......if I want to accelerate, or go up a hill.....its downshifting to fourth. Forget about SIXTH Gear..........It has to be doing 70 to even put it there......and the only place I do that is on the turnpike once a year.

ON the other hand.....IF you drive everywhere at 70 mph.......I am sure its useful. So ask yourself......do you drive everywhere at 70 mph....and that will justify an overdrive. Or....maybe people just are fine with bogging an engine down at low RPM.....I for one don't like it, and its not impressive enough for a Corvette.

The point is.....to the OP.......realize how the car is going to drive with an overdrive....and make sure its in the typical driving range / RPM / speed you intend to drive. Otherwise,....your spending alot of money for something you will never, or rarely use. That is reality.

My 69 is going to have a Mark Jone VortecPro 468 big block, hopefully 500 ft lbs of torque at 3000 RPM.....and I have a Gary Ramadei built 336 rear end......what will be my RPM in fifth gear, with at TKX .81 overdrive at 60 MPH? I estimated with a 4 speed final drive of 1:1,......probably about 2400 RPM.

 

Hmmm, my C5 can pull any hill I've come across around here in 6th gear at 62-63mph with the cruise set. It pulled all the interstate and secondary highway hills through the eastern US mountains in 6th in the 65-75mph range. I don't expect it to accelerate in 6th, or really even much in 5th. That's just silly. But if the cruise is set it'll maintain the speed nl problem. I can't recall a case where I needed acceleration badly without being able to drop it to 3rd or 4th.

With a carburetor, you need to keep above the cam minimum rpm and have enough airflow to keep the carburetor venturi effect working so it fuels properly. For most milder engines that's around 2000rpm or more.

The bottom line is that you need to gear it to be above the minimum rpm of your engine at the typical highway speeds you expect to drive. This is different for every combination and driver.

 

Some people don't even recognize bogging / lugging.....and are oblivous to it, and really don't care. To me......its hard on the engine. In cruise control.....a person would not even know its doing it, other than the obvious low RPM rumble that occurs,......but if you are pushing the gas pedal down yourself....what you realize is it takes alot of pedal to get the car to even move. I don't want to abuse my engines like that. Certainly, a .68 overdrive, putting RPM down at 1500 or below at 55-60 mph is absolutely bogging / lugging. Not for me.

A car with TONS of torque may be more accomodating to that....but even this 400 ft lb high tech, fuel injected, knock sensored, fancy car is not enough. So....some low torque C3 generation 350 is not going to do well at all......but again....some people don't care, and are oblivious.

Truth is, MOST modern cars and trucks today, automatics.....they ALL are designed to bog because the EPA demands fuel mileage, and that requires the engineers to constantly make the transmissions drop RPM as soon as possible......not like pre-EPA cars did. My 2015 F150 in normal driving mode would constantly seek lower RPM....and even on a very slight grade would bog bog bog till I would get so sick of it, I would lay into the pedal....and then it would finally shift,....over-rev, and accelerate. **** poor design. All in the name of EPA BS. I drove it in the SPORT mode all the time to avoid that,.....where it would shift like an automatic should shift. Its the MAIN reason I traded it in on my C6 Corvette.....BS transmission shifting. I drive rental cars all the time.....same BS nonsense.

Do what you want.....its your car. These are just facts to help people understand what they are doing. And there are consequences. Again....if you drive / cruise everywhere at 70 MPH and up.....yep.....that fifth gear is useful. But irregardless of what people say.......I don't believe any C3 is driven more above 70 than below 70 mph. But.....for those that spend the money on overdrive aftermarket transmissions......there is a thing call confimration bias.

Sorry guys if I don't join the club.....but I think I will stick with my 4 speed for my style of driving. A TKX .81 overdrive MIGHT be borderline the right thing for my 69 big block car......but I probably won't do it....considering its another $2500 to spend on top of what I already spent on my brand new Autogear M23Z.

 

I installed the TKX 2 winters ago in my ‘71 big block. Got the kit from SilverSport, they were awesome to deal with. I converted from a TH400 auto, so I already had the removable crossmember, I’d recommend adding the removable crossmember because it makes it much easier to install.

Overall the install was pretty straightforward, honestly indexing the bellhousing was probably the hardest part, and it really wasn’t bad. I went with the hydraulic clutch setup since I had an auto and needed to buy all the clutch parts anyway. I would highly recommend it, the clutch is so easy to push and smooth engagement. I added a McLeod street clutch, wish I’d gone with a bit of a stickier clutch but that’s just my preference.

I have a 3:55 rear and I went with the close ratio with the 2.87 first and .68 fifth. I love blasting through twisties so the close ratio made more sense for me, plus with a built big block I don’t have any issues launching! 4th is fine for around town and fast sweepers, 5th is truly overdrive, I use it when I’m on the highway primarily. At 70 I’m spinning around 1900 versus 3200 before.

Feedback overall: best investment yet on my corvette. I love it, it’s a totally new car vs the auto. It’s easy to shift and makes driving on the highway actually enjoyable. I would totally recommend the TKX and SilverSport.

 

I don't see an issue with downshifting to pass. Drop a gear and disappear? That's the whole point of a manual. I'm downshifting to 3rd either way. What does it matter if I start in 4th, 5th (TKX) or 6th (Magnum)? The ratios are basically the same, you just get more gears. That was the point of the spreadsheet I posted.

@cagotzmann can get over 30 mpg with his 6-speed (and an LS3). I could do over 40 mpg when I made a point of "lugging" my 5-speed manual econobox. There's more than one way to drive these cars, and more gears = more options.