Mike6811

In an attempt to quiet down the sidepipes on my '74 4-speed with the base 195 hp 350, L82 cam and 3.36 rear end, I'm thinking of getting the Hurst Drivelines 5-speed, but can't determine which final drive ratio I should get--the .64, .68, or the .82, even though I know the RPM at 70 mph for each. Any suggestions?

Thanks in advance for all replies.

c3_dk

If it was me, then I would go for 3.70 or 4.11 rear and 0.64 transmission.
Then you get the best of 2 worlds.

79L48

If/When I go restomod, I settled on 3.55 final drive with a TKO with the .68 O/D. Crunching the numbers, it seemed like the best compromise for acceleration, cruising and mileage.

If the noise is the biggest factor, then my suggestion would be to determine at what revs you like the noises best and shoot for that. That said, go drive at a steady-state engine speed that represents where your RPMs would be for each O/D ratio and see which sounds best with your pipes.

Mako72

TKO600 /.64OD combo here. I had my engine built with torque in mind. With my original 3:36 rear end this combo works great for me. It will pull from 40 mph in 5th around town and I can run with late model Corvettes on the interstate. The .64 5th gear makes road trips a breeze and quiets the sidepipes down.

7T1vette

I think the OP is asking what the ratio of the 'High' range in the 5-speed box should be.

Not much difference between .64 and .68....UNLESS the other gear ranges in the transmission are better proportioned. Either of those is about 2/3 ratio from 1:1 and the difference in engine speed in 5th range on the highway (70 mph) would be negligible between them; either will yield about 2000 rpm at 70 mph.

All things being the same, I'd go with .68 for your 3.36 rear gear.

Mako72

TKO 500 - 3.27, 1.98, 1.34, 1.00, 0.68
TKO 600 - 2.87, 1.89, 1.28, 1.00, 0.64 or 0.82

Lupigiato

I just bought the TKO 600 with .64.

flyeri

I have a .64 TKO with 3.55. That works fine with my ZZ454. The previous engine had too much cam for that setup and was not happy trying to drive anywhere below 60mph (1700-1800 rpm). If I had your 3.36 I would get the .68. My two cents.

lowbuck72

I have a T5 with a .63 5th and 3.36 gears. This works out fine as long as you treat the 5th as just an overdrive for freeway cruising. It's a pretty big gap from 4th to 5th.

terrys6t8roadster

With 3.73 in the 6t8 I went with 0.82. Would rather have the 0.64 RPM always to low for any power in 5th. T

CPTCroaker

I would plug the numbers into an RPM calculator like this one:


http://www.tremec.com/calculadora.php


Then take those RPM numbers and run your car at those levels. This way you can actually gauge the noise your side pipes will make at the rpm levels these different gears put you at. From there you can gauge how fast you want to accelerate keeping in mind your cruising RPMs.


Personally I would go with the .64 fifth with your 3.36 as it would give you around 2000 rpms at 70mph and keep your noise down.

Dynra Rockets

What ratio is best is very subjective, everyone likes something different and different engines have different powerbands.

My 350 is built around torque (11:1, .390/.410, dual plane intake) so the .63 5th in my T5 is great.

Mike6811

Thanks for the replies, especially the ones pertaining to the RPM-and-exhaust level test, which I'll perform.

Since my motor is the base 195 hp version, with no upgrades in the future, would I still have enough power to use the .64 or the .68 final drive without lugging?

7T1vette

As long as you have rpm higher than 2K and aren't overloaded or going up a steep hill, you should have no problem. 350 SBC engine has plenty of low-speed torque. But, I wouldn't go into fifth range unless at highway speeds (65mph or higher). This issue is why I would recommend the .68 final ratio; it's more useful in normal working range.

Remember that 4th range in either TKO tranny is the same as what Hi-range in the present trans provides now.

Tiger Joe

one thing to remember with the .64 vs .68 is the entire gear spread for the trans is changed. Mainly the .68 s in the TKO-500 and comes with a 3.27 first gear and the .64 is the TKO-600 and comes with 2.87 first.


I think there were 2 muncies available in 74 (wide and close ratio) but the tallest first gear is only 2.52 other is 2.20. either would be a big jump to 3.27 first.


Id go with the tko-600. that's what I have in my 67 C10. like already said, you don't have to use 5th around town, which you wont most of the time, but man its nice to have that 1/3 rpm drop on the highway.


ps- I used hurst driveline for my trans and couldn't be happier.

c3_dk

With a 195 hp engine, then a T5WC 5 speed maybe enough.
I have 1352-176 that will come into my 69 convertible.
It is the first year for WC, and the last year for man. tach drive.
Also 1352-176 has a nice fast 1th gear, and 5th gear is 0.63

1th 2.95
2th 1.94
3th 1.34
4th 1.00
5th 0.63

http://www.britishv8.org/articles/bo...t5-id-tags.htm

Ibanez540r

This is very subjective. I did the same research.

The .64 is the more popular option, as you have seen here. IMO this comes from most guys haven driven their 3 speed auto or 4 speed man for years and years, sick of the high RPMs and wanting the best drop possible. However, your area, driving style, and intent come into play. Will you be going on road trips or traveling on the interstate for extended periods of time? Do you use your car as a cruiser? If yes to most of those then the .64 is the right choice. OR Are you more suburban around town, jump on the interstate for a short time with only occasional longer trips, and maybe get out on the back roads for a cruise? Then the .82 may be better especially with the 3.36.

With the 3.36 and stock motor the .64 is going to be a highway OD gear only. Around town etc. you'll have a 4 speed. Get on the highway, get up to speed, drop it into 5th and cruise. Need to pass strong? Downshift, do what you gotta do, and drop it back to 5th to lounge down the road. The .82 will be more useful day to day with a smooth transition through the gears on everyday roads and cruising around town. You'll be able to row 1, 2, 3, 4, 5. It will still be a comfortable improvement at highway speeds, but not nearly as drastic as the .64.

Lots of happy .64 owners (even more popular with higher numerical gears) but people like GKull and Pauldana regretted the .64 and opted for the .82 because of the drastic separation from 4th.

If I would have taken the popular vote for face value with all the forums I read through on the subject, I would have went with the .64. But I noticed a trend with the occasional guy that preferred the .82, usually more performance oriented driving the car hard and not too interested in getting on the highway for extended periods of time. That more closely matched my build and goals so I chose the .82

Dynra Rockets

Ditto. I have the -176 also and love it with my my engine.

M. Young

I have the TKO-600 with the .64 and love it.