Any opinoins out there weather to go with a .82 or a .64 OD for a 5 speed trans.

Swaping in a 454 HO Create engine in a 1974. The car has 3.36 rear gears. Kiesler recommneds the .64 OD with higway cruising at 70 MPHs RPMs would be around 1700. Hurst adivses that the the engine will be loading up and I should go with the .82 to bring the RPMs up to 2100 to 2300 Range

Live in LA lots of freeway driving just want to cruise no road racing in future Really interested in anybody who has made the upgrade

Thanks

 

With lots of freeways, you might want to go with the .64. I have 3.70 rear gears with a .74 5th and .50 6th T56 trans.

 

The engine manufacturer is right. I have more power than your 454 with 3.55 gearing. The jump to .64 overdrive is too big and the rpm drop is so much that your lugging your engine.

I would not recommend the .64 to any one. I wished that i had bought the .82 Down the road when my tranny needs work I will rebuild it with the .82 gear sets

 

I went .64.... MISTAKE. :toe tap: next time i trop the transmission for a new clutch disk set, I will switch out to .82

 

The .64 is great if you have a stock or mild cam that makes strong torque down low in the RPM range. If you have mild to wild cam, you will be battling fouled plugs, surging and horrible gas mileage!
From what I've read the 454 HO is a mild cam with ok compression. So IMO you can go either way depending on your driving habits. I'm a fast driver 80+mph on the highway so I would go with the .64! If you're the 70 mph guy that go with the .82

 

I have the rs500 from Kiesler which I believe is .66 with a stock zz4 crate engine and 3.36 rear
No problems at all. The combination can still excellerate from 40mph in 5th.

 

As others have stated, if you cruise at 70 MPH 90% of the time, I guess you could go .82 but I would not. If you routinely cruise at 80 MPH, I would definitely go with the .64. I don't know which 454 crate engine you are going with, but the GM crate 454 listed below is fairly mild and makes 500 ft-lbs torque at 3,250 RPM-500!!

454 HO Technical Information
Horsepower ..................... 425 @ 5250 RPM
Torque .......................... 500 @ 3250 RPM
Max. Recommended RPM ..... 5500
Compression Ratio ............. 8.75:1Block ............................ 12550307 Cast Iron - Four bolt mains
Crankshaft ...................... 14096983 Forged Steel
Connecting Rods ............... 10198922 Forged Steel
Pistons .......................... 10215228 Forged Aluminum
Piston Rings .................... 12523921
Camshaft ........................ 24502611 Hydraulic rollerLift: .510" I, .540" E.Duration @ .050: 211o I, 230o E.
Timing Chain ................... 10114177 Single Roller
Cylinder Heads ................. 14096801 Cast iron 118cc combustionchambers
Intake Valves ................... 14097045 2.19"
Exhaust Valves .................. 14097049 1.88"
Valve Springs ................... 14097002
Rocker Arms .................... 12523976 1.7:1
Torsional Damper .............. 10216339 8"
Flexplate ........................ 10185034 14"
Valve Lash ...................... Net lash
Fuel ............................. 92 Octane
Spark Plugs ..................... MR43T Gap .045#10 Rapid Fire Gap .045
Ignition Timing .................. 4° BTDC


The engine above has OVER 400 ft-lbs torque at 1,750 RPM!!!

With that kind of torque in a mild/moderate street engine, the .64 OD will be fine and should be no issue, especially with a 454. You always have 5th if you need less OD. Heck, my 10 Z06 will cruise all day at 70-80 MPH in 6th @ 1,800-2,100 RPM because it has tons of torque. If you are not racing, .64 ,and if you want the best fuel economy you can get cruising. I bet that baby could get easy 20 MPG with that overdrive or more.

 

Zz4 is a nice all around engine and I agree the motor can grunt it's way up from low rpm but at cruising speed you want that 2000-2200 rpm for a mild cam. That's probably right where your at at @70. At 80mph it might start revving 2500-2700 rpm
When Din stated he was going 454 high output. That can mean many different combos to many different people. I assume he was referring to GM crate.
His real time driving habits will be a major factor. I run the stock 2:67 rear with .68 overdrive and I'm dead on 2000 rpm at 80 mph. I was thinking of hunting down a 3:08 rear because they're all over but this rear needs to blow first!

 

I just added an OD to my 3.73 rear end 427/390 '69.
Mine is a convertible with side pipes.
Roaring down the tollway at 65 spining 3,000? rpm was friggin loud. Plus, I was in the slow lane. Yeah, Joe Cool in the yellow Vette was poking along because I was out if gears.
I bought the American Powertrain 5 speed and it has a .64 OD. Now, cruising at 80mph is quiet.
It does seem like a big jump from 4th to OD, but even cruising on the boulevard at 45 in OD is very tolerable. The big torque of the big block can move the car just fine without lugging. Granted, I'm not stomping on it in OD poking along at 1,300 rpm, but I can definitely accelerate.

I thought my first gear ratio would almost be superfluous with the 3.73:1 rear. I can easily get underway from a standing start in 2nd gear.
But now that my clutch has a hundreds of miles on it, I've stomped on it a few times starting in first gear. Holy smokes my car goes!

I think you'd have more fun adding the 5 speed and changing to rear end with lower gears!

 

The GM 454 HO crate engine has 150hp and 450ft-lbs of torque @ 1750rpm so it's quite capable of pulling the car down the road at that rpm without lugging and loading-up.

It has nothing to do with peak power, it's the power available at the cruising rpm that determines how it'll work. A small block with more compression and a larger duration cam will need more rpm to keep it happy even if it makes the same 425hp that the 454 HO is rated for.

As hugie82 pointed out, the answer also changes depending on how you expect to cruise on the highways. Is 70mph the max or will you often see > 70mph? Also, give some thought on how often you might go on trips or cruises where you are wanting to do say 60mph or 65mph.

gkull or pauldana - have either of you got dyno curves for your engine down that low?

 

The engine specs I posted above were for the 454HO GM crate engine-425 HP. I did not post but referenced above also the >400 ft-lbs torque on the graph that was on the page where I got the stats above-Thus my comment that with 400-425 ft-lbs of torque at 1,750 RPM (from the GM chart)-zero issues. If any engine is made for a .64 OD, it's the 454. I really think that the issue has nothing to do whether the engine can cruise at 1,700 RPM (it can easily-end of discussion, ESPECIALLY with a 454) but whether you want low revs or slightly higher revs.

 

With my 3.55 and .64 I generally don't shift until about 65-70 It can do it seems happier to drive around 75 and up. The poster has even lower gearing at 3.36

The real truth is a motor gets the best MPG in its efficiency rpm range. So under rpm is as detrimental as over rpm. I would rather run 2000 rpm on the highway than 1750 and be lugging

 

Here's a thought ... with .64 you can always drop into 5th OD (or direct 1:1) if you experience "lugging" on your 454 CI @ 1750 RPM ... which I doubt with 450 lbs torque at that RPM ... that's humongous torque down low. BUT if you get the .82 OD then you can never go higher.

An engine is just an air pump and pumping less air/fuel means better gas mileage period.

 

I recall you having a rather stout small block, maybe a 383 or 408? If that is true then it would not be fair to compare the best operating point of your engine to the 454HO.

So far there is a fairly equal mix of yes and no. I don't see either answer coming out on top because every car and engine is different and how the car "feels" to each owner can also come into play. Different people want their cars to have different amounts of "go" in high gear.

 

434 and 454 aren't that far apart and i have lots of compression to build TQ throughout the rpm.

the big jump to fifth is like a freeway gear only. Even when I ran 4th to red line and shifted to 5th it just looses the power band

 

That's because 5th is a freeway gear,

I'd bet your cam has a higher operating range than the 454HO.

 

Thanks everybody for their input. Gkull and pauldana's argument is consistent with Steve's over at Hurst. And that is the .64 with my rear gears, engine and tire size would too much of a RPM drop.

With my set-up the .82 will have me cruising around 2200 RPM at 70 MPH which would avoid the engine lugging and keep it in the power band in case I need to put my foot into it

Once I get the tranny I will do the engine swap, old engine is out now and the new one is ready to go, and update the forum hoping I can help someone like you guys have helped me

Thanks again for all your input

 

The dual OD of my ZF6 is much more functional

 

i had no problems with my 383 cursing in od, ... thats not the entire point here... the jump from 4th to a .64 od is just to much for ANYTHING other than cursing and gas savings... throw all hopes of ANY performance 5th type gear out the door...

 

well I only have a 406.....I drive on the hiway all the time and my engine with the .64 OD is happy most of the time...unless someone is going 50 mph. I can easily pull out and pass at 60 MPH without shifting down, and there aren't any complaints from the engine.

Oh...I have 336 gears also. I think I'd be happier with 355's though