Vandy2018

Does Tremec make a 6 speed for the 61 or is a five speed adequate. What about cost?

Factoid

Here you go.

https://shiftsst.com/articles/cat/ge...erfectfit-kit/

GTOguy

I like the idea of a 5 speed for an overdrive gear. I have zero enthusiasm for an extra overdrive gear, though. I think 5 gears would be enough. 4 are good enough for me currently.

Lotsacubes

Wouldn’t want or need another gear. Have the TKO600 with .64 OD and 3.70 rear. I think it’s about perfect for me.

Vandy2018

Thanks
I put a 6 speed in my 427 ‘68. Love it. Still pulls hard in the lower gears and only 1800 rpm at 80 mph. Saves gas and the motor. Just wondering if anybody put one on a 61.

GTOguy

One issue I've run into with the deep, deep overdrives is exactly that: the rpm at cruise is so low that the engine is running 'off the cam' and is lugging. Which is not optimal, especially if you have any kind of performance cam. For modern engines with variable valve timing and mild camshaft profiles, it is the norm. None of the engines in my classic GTO's or my Corvette would be happy running 1800 rpm at 80mph....they need to be at about 2100-2400 rpm to be at the beginning of their powerbands and to not be lugging and mushy. A good friend put a deep OD in his '48 Ford F1 pickup with a Boss 302, and we were unable to use the overdrive due to his already lazy 2.75 rear gear. Changing that to a 3.50 rear gear solved the problem and brought the engine rpms back up to about 2300 at 80 mph....and into the beginning of the engine's powerband.

mark6669

I have both transmissions even if you never use 6th gear the smother shifting of the 6 speed is worth it. The 5 speed shift rail system dosen't like high RPM shifts it has been discussed in a few previous threads.
Mark

Vandy2018

I Agree The 6 speed is sooo nice my 68 runs very comfortably on the highway in 5 th gear so having the extra gear is nice for a long trip if you wanna save some fuel. Did you have your 6 speed in a C2?.

mark6669

I have the 6 speed in a 69 with a 3.42 rear the 5 speed is in my 63 coupe I did not want to raise the tunnel but I am rethinking that decision. Both cars are LS powered restomods.
Mark.

Vandy2018

How many RPMs in the 70-80mph range? I would rather do the TKO 600 if they dont have to modify the tunnel.
thanks

toddalin

Well...,

I have the TKO600 with the 0.64 OD and 3.70 gears and 225/60/15 tires, and I wish it was a 6 speed.

It's a long way down from 5th to 4th coming off the freeway and you can easily "lug" 5th gear in freeway traffic where that extra gear would be just right.

Crunch527

For the TKO600, I’ve always thought the .64 was too big a drop and the .82 not enough. I’d rather see a TKO600 with a 5th gear ratio in between. To kind of address it, I like to run a 4:11 gear with the .64. As GTOGuy pointed out, I have found the 4:11s give enough RPM in 5th (2300-ish) to keep it off the cam. It’s still all done when you get to 5th. However, I get it, its more about marketing the “overdrive.”

Since it sounds like you are using a LS platform, I’d say do the tunnel and run the 6 speed. I love how the LS motors pull like freight trains through all the gears and you can have an overdrive...much fun!!!

Factoid

You guys just need more torque down low!

solidaxel

And after running thru the gears 4th 5th 6th, just how fast do you think you will be going?

95% of my driving is in the city and can not go any faster than the guy in front of me

The other 5% is 45mph to highway speed in Az is 75mph...........and no one in front of you!

I have a TKO600 with the .64:1 OD with 3:73:1 and stock ZZ4, with factory cam with 74000 miles and I use 5th
as soon as I can, skip 3rd most of the time

I think the 6Speed O D is .80 for 5th and .64 for 6th gear

Have fun driving in the city between stop lights!

Drothgeb

I have a 61 with a 383, 3.73s and a TKO 600 .82. It works perfect for driving the country roads I normally drive. The gear spacing feels good to me. Normal driving I use 1-4. On the open road I get in 5th. For driving on the highway at 70mph or more, a 6th .64 gear would be nice. The engine still only turns ~2600 rpms@70mph, so it’s not bad. But in the areas with a 70mph speed limit, the traffic is normally doing 75-80mph. Rpms still aren’t bad, but a little lower would be better. A .70-.75 5th would have been perfect.

I originally wanted the T56, but didn’t want to do the tunnel mods. After driving the TKO 600 for a year now, I would still like to have the T56. As has been said, it just shifts much better.

Lotsacubes

It must be around 2050 at 70. I routinely putt around at 1400-1600 rpm just to reduce noise for conversation. My car doesn’t have a shortage of torque. The 2-3 shift is not like the Muncie, but I’m not racing or reving hard 99.9% of the time. I think SST offers an upgrade now that allows faster, smoother shifting to address the shift criticisms. But frankly if your like me cruising with your honey you’ll get used to the 2-3 shift taking 200 milliseconds longer. I’d definitely not want more revs at cruise for higher noise and unnecessary spinning. .82 just wouldn’t be significant enough drop for me. Ask SST about the carbon shifter option and tell us what they say. I’m with you. I wouldn’t be interested in cutting the glass. Cheers

Frankie the Fink

My Tremec 5-sp OD in the 61 on the highway; 270hp dual quad; 3.7 rear: The car basically cruises at a fast idle on the turnpike...the only mod is cutting off the bottom of the ashtray depression....keep the "cup" part you cutoff and it can be replaced someday for a purist.

Another speed is just for bragging rights IMO, but high RPM 2-3 shifts take some finessing - you have to learn not to "fight" the transmission; plenty of youtubes on the topic.


My car had a metal ashtray bottom installed and I never thought twice about it afterwards - you WILL have to do something with the ashtray though..


I also used an early Volvo shifter boot for the taller repro gear shift lever - the original style just kept tearing:




There is a thread on here somewhere about the details on that boot swap. Apparently a bunch of members went the same route after I posted the info.

Lotsacubes

^^^^^ great way to tell the story. I’ll be copying that Frank. Looks like yours was the .64 also. Thx

Drothgeb

I lowered the trans mount on mine slightly to improve the driveshaft angle. The ashtray fits fine with no mods.

Frankie the Fink

I don't want to get in an argument about it but there was no way that Tremec would go in my bone stock '61 with the stock ashtray - I'd have to dig out my install instructions but I think they even tell you that. If you can avoid it fine - but I wouldn't count on it. Checking bell-housing runout and driveshaft angles are imperatives to avoid vibration ore premature U-joint wear,etc...