Question for the guys running 3.73's with a 6cyl and manual trans

[curvedglass]

I bought my 63 last year for use as a daily driver. It has been awesome albeit with one caveat. The previous owner swapped out the original 3.73's in favor of 3.08's for highway driving. I don't do much highway driving and I average about 16.5-17.5 mpg. My problem comes when I go up steep hills. It is worse from a dead stop. I'm lucky if I can make it to 30-35 mph. On the move I need to build up speed so I don't lose momentum or slow down the traffic behind me. Engine has plenty of power. Even at highway speeds it just seems hard to keep it in the power band. 230 stock with Weber 2bbl replacement and an HEI, 3spd on the tree.

My question is for you guys running the original 3.73 rear. What is top speed on the highway and what rpm's are you seeing?

Back when I bought the weber I asked Tom over at Langdons about adding power and he recommended that I revert back to the original ratio and put in an overdrive trans as opposed to hopping up the motor.

I would like to start with changing out the gears but the trans will have to wait. I want to keep driving the truck daily and don't want the 3.73's to kill me too bad on mileage and wear at higher rpm's.

[jayoldschool]

Keep the gears, enjoy good mileage, downshift to 2nd on the big hills?

[curvedglass]

Originally Posted by jayoldschool

Keep the gears, enjoy good mileage, downshift to 2nd on the big hills?

That's ok for the side streets. On the major roads at cruising speed I do not want to drop down a gear. Most of the time I'm happy with the slow cruising but it is frustrating in traffic and I can't even pass a VW Bus )

[vince1]

I think 3.08 is a car ratio, in the trucks it is 3.07.

My original diff in my 66 was trashed so I put in a 3.73 from a 64. Teaching my daughter how to drive a standard (4Sp), she asked where is the next gear? I said that's it, which was met with peals of laughter.

Now it has a 3.07 that I like a lot more. If I were to use the 3.73 again it would have to have an overdrive in front of it. In your case a 5sp? Or maybe there are overdrive units available for the 3 sp?

If you look up RPM calculator you can get all that info by putting in tire size and axle ratio.

[curvedglass]

Originally Posted by vince1

I think 3.08 is a car ratio, in the trucks it is 3.07.

My original diff in my 66 was trashed so I put in a 3.73 from a 64. Teaching my daughter how to drive a standard (4Sp), she asked where is the next gear? I said that's it, which was met with peals of laughter.

Now it has a 3.07 that I like a lot more. If I were to use the 3.73 again it would have to have an overdrive in front of it. In your case a 5sp? Or maybe there are overdrive units available for the 3 sp?

If you look up RPM calculator you can get all that info by putting in tire size and axle ratio.

Copy that. I want to convert to a 700R4 at some point. One of the reasons for this truck was that you can swap in just about anything in to a Chevy. My knees are on the way out and the clutch leg is going first (

[TJ's Chevy]

3.73's will not kill your top end to badly. 3.73's and 30 inch tires for me was 3000 rpm at 65-70 I had a 292/sm420. An OD trans which I'm putting in with my new 292 will give me about 2500 rpm at 70 mph which will be perfect. Your 230 is a smaller engine, though yes indeed it has great power and luckly plenty of torque at the lower range...you'd be making ANY engine struggle to be in 1:1 with 3.07's pulling grades. Heck, I get another axle from a 66 with 3.73's....swap it out...drive it and see how you like it...and if you don't...simply swap your old axle back in. I've done it and it takes very little time.

[geezer#99]

Originally Posted by curvedglass

I bought my 63 last year for use as a daily driver. It has been awesome albeit with one caveat. The previous owner swapped out the original 3.73's in favor of 3.08's for highway driving. I don't do much highway driving and I average about 16.5-17.5 mpg. My problem comes when I go up steep hills. It is worse from a dead stop. I'm lucky if I can make it to 30-35 mph. On the move I need to build up speed so I don't lose momentum or slow down the traffic behind me. Engine has plenty of power. Even at highway speeds it just seems hard to keep it in the power band. 230 stock with Weber 2bbl replacement and an HEI, 3spd on the tree.

My question is for you guys running the original 3.73 rear. What is top speed on the highway and what rpm's are you seeing?

Back when I bought the weber I asked Tom over at Langdons about adding power and he recommended that I revert back to the original ratio and put in an overdrive trans as opposed to hopping up the motor.

I would like to start with changing out the gears but the trans will have to wait. I want to keep driving the truck daily and don't want the 3.73's to kill me too bad on mileage and wear at higher rpm's.

Don't blame the gear ratio!
What size of tires are you using? Height??
What's your initial timing set at?

[curvedglass]

Originally Posted by geezer#99

Don't blame the gear ratio!
What size of tires are you using? Height??
What's your initial timing set at?

P235/70/15 BFG T/A's
No idea on the timing.

[geezer#99]

Originally Posted by curvedglass

P235/70/15 BFG T/A's
No idea on the timing.

Try a poor man's underdrive trick to see what a 3.73 gear will be like. Swap on some shorter tires. Like 205 60 15's.
Figure out what your initial timing is!
That's the key to your lack of power.

[curvedglass]

Originally Posted by geezer#99

Try a poor man's underdrive trick to see what a 3.73 gear will be like. Swap on some shorter tires. Like 205 60 15's.
Figure out what your initial timing is!
That's the key to your lack of power.

Thanks Geez. I will throw the light on it. What should my timing be set to? I swapped out the stock dizzy for an HEI unit so I might not be spot on anymore. Although I had the same issues before the Weber and the HEI swap.

[geezer#99]

Originally Posted by curvedglass

Thanks Geez. I will throw the light on it. What should my timing be set to? I swapped out the stock dizzy for an HEI unit so I might not be spot on anymore. Although I had the same issues before the Weber and the HEI swap.

Try 14 initial.
Plug off the vac to the dizzy when you se it.
Did you run a dedicated 12v wire to your hei or hook it up to the stock wire?

[slepysal]

I have 3.73 in my 60 and am running p215/75r15 ( 27.7") and I have no "power issues" 70-75 at 3500 rpm In all truthfulness I have to stay in the slow lane 70-75 mph in the bay area is considered slow !

[geezer#99]

Originally Posted by slepysal

I have 3.73 in my 60 and am running p215/75r15 ( 27.7") and I have no "power issues" 70-75 at 3500 rpm In all truthfulness I have to stay in the slow lane 70-75 mph in the bay area is considered slow !

It's that 'Canuck' valve cover that makes you go faster Sal!!

[slepysal]

Originally Posted by geezer#99

It's that 'Canuck' valve cover that makes you go faster Sal!!

you know it !!!

[geezer#99]

I didn't mean swapping tires permenantly.
Just some shorter test tires.
A 40 buck pair of test tires is a lot cheaper than a 1200 buck gear change that you might regret after the install.

[curvedglass]

Originally Posted by geezer#99

I didn't mean swapping tires permenantly.
Just some shorter test tires.
A 40 buck pair of test tires is a lot cheaper than a 1200 buck gear change that you might regret after the install.

Oh I got ya! Around my area in the northeast outside Philly nothing is $40 though.

After all the help I got from you guys I am sticking to troubleshooting the power side.

[jayoldschool]

Fresh fuel filter? No cracks in any of the rubber fuel lines?

[curvedglass]

New filter and lines. Fresh new weber two barrel three months ago.
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[sambrutay]

l6 230 3ott 235/75/15 373 gears. 65 mph @ 3000rpm. traffic gets pissed on trips up and down I65. LOL

[Lugnutz65]

Originally Posted by sambrutay

l6 230 3ott 235/75/15 373 gears. 65 mph @ 3000rpm. traffic gets pissed on trips up and down I65. LOL

Install an OD tranny with a 0.73 5th gear and the RPMs will drop to 2000 - 2100 at 65 MPH with those same tires. Better MPG too.

[sambrutay]

lugnutz, I really want to. would love to do a factory style 3 speed od. Have been looking for 5 speed s-10 trans but hard to find with no electric speedo.

[Lugnutz65]

Originally Posted by sambrutay

lugnutz, I really want to. would love to do a factory style 3 speed od. Have been looking for 5 speed s-10 trans but hard to find with no electric speedo.

I will send you a PM with tips on how I find them.

[slepysal]

Originally Posted by Lugnutz65

I will send you a PM with tips on how I find them.

I want tips too (please)

[frankslagoon]

how about putten a Saginaw 4 speed in. that would give ya an extra gear on those hills. but ya can't use the columm shift. I've got a couple 3 sp. overdrives and they ain't hard to find . but my 283 just barely has the power to really work one even with 3:73. GM never used any rear ends higher than 3;73 with the 3 sp. O/D in any vehicle

[sharkskinman]

Ooo Ooo I want a OD for my 3 spd
Might want to upgrade to Saginaw syncro