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What rear gears do you have?

Even with 3.31s I was able to use my 0.63 6th gear on the highway.
3.73
I need to switch to a smaller cam
My cam is 250/256 @.050 on a 108
It likes to surge at anything below 1700.
If I had something in the 231/231 range I bet it would be able to handle that .63 OD much better.
 

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3.73
I need to switch to a smaller cam
My cam is 250/256 @.050 on a 108
It likes to surge at anything below 1700.
If I had something in the 231/231 range I bet it would be able to handle that .63 OD much better.

Big cams definitely are tougher to work with at low RPM's in high gear. I wonder how much is the duration itself, and how much is the overlap. Plus I wonder if EFI could be tuned better at those RPM/loads vs a carb.
 

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Big cams definitely are tougher to work with at low RPM's in high gear. I wonder how much is the duration itself, and how much is the overlap. Plus I wonder if EFI could be tuned better at those RPM/loads vs a carb.
I thought I replied to this.. But I may try to richen it up to 14 like yours is. I currently run 14.8 which might be why it surges below 1800. I doubt it though, the cam is relatively large.
 

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My 66 came to me and I drove it for 5 or 6 years with the TH350 and 331 gears. Max trip was 50 miles at 70 or 75 on the interstate. Loud and miserable.

So I skipped right over the four speed deal and tried a T5 with a .90 od. If fit with no cutting, but the Od was not much.

It proved my stick conversion, and a tko 600 found it way in there. Some tunnel tinwork, yes, but now it will cruise the interstate anywhere anytime and stay with traffic. And that's with a 373 gear upgrade.

So much more fun and useful.
 

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I installed a Tremec TKO 600 in my 68 Chevelle last winter. It is powered by a 350 with an Edelbrock rolling thunder top end kit (E-tec 170 heads, hydraulic roller, air gap intake) rated at 430 HP and 3.73 gears. I love the trans and the driveability. I used OEM pedals and clutch linkage. The floor required minor tunnel mods. I ended up raising the tunnel about one inch in the center. It is unnoticeable with the carpet installed. With a 275/60/15 tire, I can cruise 75 mph at 2200 RPM. I put 2000 miles on it during Power Tour with no complaints.
 

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I haven't heard anyone here mention the Richmond 5-speed OD and 6-speed...

The Richmond 5-speed (and 6-speed) will be almost a direct swap for the Muncie: same overall length means using the same driveshaft (may need a different slip yoke depending on the model/ output size/splines), same basic shifter location (on the side), bolts to the stock bellhousing, and uses the stock clutch (but depends on the model and your current clutch, comes in both 10-spline and 26-spline configurations as the stock Muncies. And most important, IMO, NO tunnel mods ( I did use a BFH for the Long shift linkage heim joint).

IIRC, I may have slid my crossmember back on the frame a few inches (I think the front hole in the crossmember lined up with the rear factory hole in the frame).

You might even be able to find an older version (Doug Nash)…


I ended up swapping in a Richmond Road Race version in place of the Muncie. Easy job... But it was the non-OD version (1:1 5th). But I wanted to build a new rearend (the rearend belonged to my other Chevelle), so I built a 12-bolt with 2.73 gears and positraction… With the 3.04 first gear and 2.73 rears, it was similar launch to the factory M21/3.73 or M20/3.31 set-ups. Another bonus, IMO, is the 2.73s kept the driveshaft speed low. Even with OD, you may be spinning your driveshaft too fast for its design (or figure $$$ for a new driveshaft)...
 

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Discussion Starter #29
Hey guys, so I took the ole girl out last night when I went to the gym and there's about 5 miles of straight between here and there. I ran it in 3rd (1:1) and the RPMs are higher than I estimated, its more like 2800 @ 60 mph. I checked a couple online calculators to make sure that was right, and it appears to be. The torque is right under your foot and fun, but that's just too much RPM for my taste. I guess I'll just save my pennies for a McLeod or Richmond, keep my eyes peeled for a nice used unit.
 

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I installed a TKO600 in my 70SS last winter. For what your looking for I would never spend the money on T56. My TKO from Silver Sport went in with no tunnel mods, just had to tap the floor up a little around the shifter hole. Best thing I have done to the car. I have 3.73's and it is a joy to drive on the highway now. I came from an M0 and have ZERO regrets.
 

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There is a mod that can be done to the case of the Tremec transmission that is supposed to make it able to be installed without having to cut the trans tunnel. There may even be info about the case modification on Silver Sports website. Probably can get better info about it from site members that have that done than you could from Silver Sport.
 

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There is a mod that can be done to the case of the Tremec transmission that is supposed to make it able to be installed without having to cut the trans tunnel. There may even be info about the case modification on Silver Sports website. Probably can get better info about it from site members that have that done than you could from Silver Sport.

As I posted my TKO600 from Silver Sport needed no tunnel mods, they trim the case down and it fit as advertised. They were great to deal with.
 

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I'd rather have 3.23s, a wide ratio four speed, a big motor with a smooth ideling street camshaft profile on a wide lobe separation 112-114. No higher than 9 on compression, 8.75 would be best...
 

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big block car with power down low? switch to 3.08 rear gear. small block car with that 450hp up high? switch rear to 3.42. Sounds like you have your Muncie all set up to go....it is a relatively easy swap on a 68-72 - especially the clutch junk... jmho....
 

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Discussion Starter #35
big block car with power down low? switch to 3.08 rear gear. small block car with that 450hp up high? switch rear to 3.42. Sounds like you have your Muncie all set up to go....it is a relatively easy swap on a 68-72 - especially the clutch junk... jmho....
I've got a Blueprint 355, dyno sheet said 425 hp/tq, take it with a grain of salt I suppose, but that's what I'll tell you if you ask ;-)
 

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Yes, the factory drive shaft causes problems many time when using an overdrive transmission with low gears in the rear end. The drive shaft spins too fast and causes a vibration through the whole car.
I used the factory driveshaft in my 68 when I installed my TKO. I had it shortened to fit the new combo and I have yet to experience any vibrations at any speed. Granted the OEM shaft was in excellent condition and I took the time to check the driveline angles when I installed the transmission. Eventually I want to build a new driveshaft, but the OEM piece worked to get the car on the road for PowerTour.
 

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I have an M22 auburn gear trans with 3.73:1 rear, same tires you have.

Sometimes I wish I had overdrive, but, it sure is fun on the street.

My take on the 5 or 6 speeds is, shift, shift, shift, shift, shiftshiftshiftshsaeie[jaf'l;k AHHHH!

With a bunch of torque you don't need a bunch of gears.

If you want better gas mileage and cruise speeds, get a 6 cyll Nova. just sayin
 
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Discussion Starter #38
If you want better gas mileage and cruise speeds, get a 6 cyll Nova. just sayin
I hear ya and the probability of highway travel its relatively low, so I'm inclined to run the M20. I live in the NE, which means winter is 6 months long, I don't get to put a ton of miles on my car every year. Fuel economy is not at the top of my list by any means, it's the 2800 rpm just to cruise the two-lanes that's making me hesitant. The cheapest way to remedy would be to just swap out the rear gear set for something taller, something to make the 60mph more tolerable.

If I'd just hit the jackpot, I'd have the bank to sort out a plan and do everything front to back all at once and not have to revert a change I just made haha.
 

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My take on the 5 or 6 speeds is, shift, shift, shift, shift, shiftshiftshiftshsaeie[jaf'l;k AHHHH!

With a bunch of torque you don't need a bunch of gears.

If you want better gas mileage and cruise speeds, get a 6 cyll Nova. just sayin
That doesn't really make sense. With a 5 or 6 speed one has basically the same gear ratios 1 through 4 as a 4 speed transmission so if fact it should be the exact same amount of shifting . The 4th gear ratio on a 5 or 6 speed trans is 1:1. The 4th gear ratio on a 4 speed transmission is 1:1
The difference is out on the highway with an overdrive transmission one has the option of shifting to another gear where the ratio is less than 1:1. With an overdrive transmission one could choose to never shift beyond fourth gear, In that case it would be identical to having a 4 speed transmission.:yes:
 
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