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Jimi G 10-04-2006 02:25 PM

TKO600---.64 or .82
Hey guys, I was just wondering, which 5th gear do you prefer in your Tremec TKO600's the .64 or the .82, and a brief reason if you don't mind. Thanks in advance for your help.

Zoom This 10-04-2006 02:35 PM

A lot of guys prefer the .82 5th gear since the revs don't drop off so dramatically from 4th to 5th. Personally, I like the cruising rpm of the .64 ratio on long trips. If I were to opt for a .82 in my SPF, I would be much more comfortable if I changed the rear end ratio from 3.73 to 3.27. At 70 mph the .82 is revving around 2500 rpm with the 3.73 ratio. I have no complaints with over 3 years on my SPF with the .64 OD. Last year I changed from a Tremec 3550 to a TKO-600 and I opted to stick with the .64 OD.

xlr8or 10-04-2006 02:44 PM

I have the .64 in my car and don't use 5th unless I'll be driving over 75 MPH for an extended period. I have a 3.31 gear so at 2200 RPM I'm pulling 80 MPH.
I'm sure the small block cars wouldn't be happy at that RPM.

Actually I'm considering pulling it out and converting to the .82.

Jimi, Do you have the parts available to do the conversion? How much?

427SnakeSC 10-04-2006 02:45 PM

It all depends on what your final drive ratio is. Have a look at the Best/Worst Decision for a SPF, thread.

trularin 10-04-2006 02:55 PM

I have a rather stiff rear gear and the .64 is great.

xlr8or 10-04-2006 03:16 PM


Originally Posted by 427SnakeSC
It all depends on what your final drive ratio is.

Ain't that the truth. For a big block car with a 3.31 type final drive TKO600 is a great gear spread on the 1-4 and much better than the 3550. The .82 works great with this combo and is very useful. I couldn't find a .82 when I needed the trans so I settled on the .64 and it's useless except for extended cruise mode.

HSSS427 10-04-2006 03:34 PM

Got the .82 cause I never used 5th gear with my old 3550, even when cruising on the interstate the RPMs just seemed too low.

Tony Aprile 10-04-2006 03:51 PM

I originally had a TKO with a .68 overdrive and the standard 3.73's, I didn't like the useless first gear and the 1000+ rpm drop from 4th to 5th.

I changed trannys to the TKO600 for the close ratio 1-4 and the .82 overdrive but felt if reved a bit too high at highway speeds with the 3.73's, so I went with a 3.27 gear and I feel this combination was a major improvement in driveability


jwd 10-04-2006 08:44 PM

After talking to everyone who would listen, and test driving/or riding in several cars with different combinations, I went with the TKO 600 w/.82 and 3:25 rear gears. This combination will give a usable first AND fifth gears.

turnpike boy 10-05-2006 03:46 AM


Originally Posted by 427SnakeSC
It all depends on what your final drive ratio is.

This is the bottom line.

Went with a 3550 and .68 5th gear....but have 4.09's in the rear. With a 28" tall tire this works out to an equivalent 2.78:1 final drive ratio (in 5th), making for fine cruising on hiways, and dandy performance around town. 4th is good up to about 60 mph (around 3000 rpm).

All depends on your preferences - and on your final drive.

Naumoff 10-05-2006 04:55 AM


Originally Posted by 427SnakeSC
It all depends on what your final drive ratio is.

And what engine you are using.
Cruising at 65MPH at 3000rpm is fine for me.

For most with a 4 speed I think a 3.31 and a wide ratio would be a better street trans.
The Close ratio in a parking lot you are on and off the clutch pedal as the 1st gear speed is pretty fast but I can live with it as the acceleration from a stop light is incredible. Long legs and they go all the way up.:D
I took the car to the 1/4 mile drag strip and made a few passes I was at the traps in 3rd gear at 6000rpm. I shifted but could of finished the 1/4mile in third gear as the engine was still pulling.
Not that this is a drag car.

DonC 10-05-2006 07:13 AM

For what it's worth I went with the 0.82 fifth on the newer TKO 600 with the 2.87 first gear ratio and 3.07 rear end pushing 17" rims. Very pleased with the driveability of the setup.
Cruising at 70 puts the RPM's at about 2200.
Spent a lot of time with the gear calculators before I finalized on the setup with several criteria driving the decision.
First of all I have the car to drive it. 14000 miles in two relatively short (3 1/2 month or so) driving seasons here in the northwest.
Went with the 17" rims for the greater selection of tires available vs the 15".
3.07 rear as a happy medium between acceleration and cruising.
My big block is a very mild build with 450 HP and 475 lb/ft of torque. It allows me to poop around at 35 mph in 4th all day long if I need to and have a very comfortable ride.
If I was more interested in straight line acceleration I'd probably go with a rear end in the 3.27 or 3.31 range but for me this combination works very well.
For straight line I can't really say since I've never gotten around to stripping the car but at the London Cobra Show I was consistantly at 96 mph on the Main Street Burnouts which, as I understand it, was a generous 1/8th mile.

Naumoff 10-05-2006 10:20 AM

See DonC it depends on your engine. Long stroke with low end torque 428.
Engine has to be taken into consideration on rear end gear and trans gearing.
I do think a TKO600 with a .82 would work fine with my set up with 3.31 but I think it would be even better with 3.54s.

The engine you are building has alot to do with the gears you choose.

Chaplin 10-05-2006 01:34 PM


Originally Posted by Naumoff

The engine you are building has alot to do with the gears you choose.

And of course, that has the most to do with the RPM range of the cam you choose. Make sure your final drive ratio works with your cam profile.

Naumoff 10-05-2006 02:06 PM


Originally Posted by Chaplin
And of course, that has the most to do with the RPM range of the cam you choose. Make sure your final drive ratio works with your cam profile.

Thanks Chappie for making that clearer.:)

Chaplin 10-05-2006 04:05 PM

I do what I can :p

Mister 10-05-2006 04:49 PM

Yep, "Make sure your final drive ratio works with your cam profile.", Wish I had.

.64 fifth, 3.42 rear, 15 inch wheels and a cam that isn't real happy til 2,200..........fifth is only good for cruising at speeds that attract unwanted attention in Pa.
I wanted 4 for fun and 1 for cruising which is what I got. BUT the .64 is just too long for my little engine in our West Pa. hills.

Jimi G 10-06-2006 08:35 AM

With the agressive cam ratios you guys go with it sounds as though the .82 might be more desireable since there is less of a drop off from 4th to 5th. But to each his own, I personally would prefer the .82 because I would want to use a light big C.I. small block, that would have a cam range that started around 2,000 rpm and went to around 5,500 rpm. But thats just me,I like'em loud and crisp.

Mike Bartlett 10-06-2006 09:50 AM

This is at the top of my list for upgrades on my car.

My .64 T600 5th is uselsss. At 70 mph I am turning about 1800 rpm's which causes the motor to ping. I have 295/15 rear tires, 3:31 rear gears and a cam that doesn't kick in until about 2200 rpms. I guess I will try to find the .82 5th gear and related parts needed to change the OD ratio. If I drive about 85mph and above all is good. The problem is with the ever increasing traffic it seems 70 on the local freeways is about all you can hope for. Besides the cops are not real wild about me driving 85-plus.


Toby 10-06-2006 09:52 AM

I second what Mister said...

I went with the higher 5th in my TKO600 and regret it because of my cam profile. At 70 mph in 5th it absolutely lugs. I should have gone with the "road race" .82.

3.50 rear gear, 347 at about 400hp.

Hope this helps you,


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