Thread: Project "Left Overs"

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Originally Posted by Itoldyouso

Not huge progress for either of us, but progress nonetheless.

Don

Any progress is better than no progress (like me)...

S-10 rear ends are good ones. As you said, plentiful, strong, and not too wide. (Another good rear is Toyota truck - they are also plentiful, came in a bunch of different gear ratios, many of them are posi, and they have a Ford bolt pattern - 5 on 4 1/2.) I have an eight-inch Ford "one wheeler" under my coupe, but it digs with both wheels when I nail it anyway. It has a lot to do with weight distribution and the type of rear suspension.

This should be a fun thread. You are at the part of the build I like best - chassis fabrication.

Thanks Steve and JIm. I know the S10 rear won't fit into the overall old look I am shooting for, but it won't be seen. I plan on putting the radiator and gas tank in the bed and putting a louvered tonneau cover over it, so no one will know what kind of rear I am running. The 3:73's should be good cruising gears, especially with the torque of the Olds engine. I ran 3:70's in my 27 for years and now wish I hadn't put the 4:30's in there.........and to think I was actuallly considering ordering 4:56's. How did we put up with 4:88's and 5:13's in some of the cars we used to have?

Don

I for one, and I'm sure many others would agree, would be very happy to never see your rearend.

I'm with unc,

The visual I'm getting is too much to bare.

Jack.

Bobby is always there with a rear end to scare us all!
Don I'm with Jim, better any progress than no progress! I'm stuck in a rut for awhile until it starts to dry up around here, and warm up. Sounds like a great deal on the rear axle. I think I paid around 350 for mine. After reading a lot of blogs, I went with a 3:0 which probably will result in the opposite problems you are talking about, but around here there are a lot of highways to drive to get to shows like Hot August Nights, and I figured the low revs at highway speed would be nice!

Hey, there was a time people would have paid good money for that privilage! Oh wait, that was just a dream I had..........sorry.

Steve. I would have been very happy, maybe happier, with a 3.0 actually. That is what I had in the 23 and it was perfect, even with 30 inch tall slicks. Cruising at 60-70 I was just slightly off idle and with the mild cam it got fantastic milage and still scooted when I got on it. You will like that ratio. But I figure with the 3:73's and also 30 inch tall slicks it will be still ok on the highway, and maybe a little better in case I decide to race this one at this years Billetproof drags.

Don

Don my gearing is 3.50 on my 32 with 31" tall tyres, The olds pulls it with ease, those 3.73's will certainly zipp it off the lights

Originally Posted by Itoldyouso

Hey, there was a time people would have paid good money for that privilage! Oh wait, that was just a dream I had..........sorry.

Steve. I would have been very happy, maybe happier, with a 3.0 actually. That is what I had in the 23 and it was perfect, even with 30 inch tall slicks. Cruising at 60-70 I was just slightly off idle and with the mild cam it got fantastic milage and still scooted when I got on it. You will like that ratio. But I figure with the 3:73's and also 30 inch tall slicks it will be still ok on the highway, and maybe a little better in case I decide to race this one at this years Billetproof drags.

Don

Thanks Don. I was getting worried with the low ratio. Never done this stuff before. That little RPU with that beautiful big block is gonna burn those new tires(Tyres for our English friends) of yours in no time!

Steve, the strange part is, I ran 3:70 gears in my 27 for years and it went down the road at highway speeds just right. So, I figured how big of a change could it be to go to 4:30's? Well, it is a BIG difference. They are fine around town, but I hate them on the highway.

When I was in the car club we had a member with a 29 roadster that had 4:10's in it, and everyone complained that he was always dropping behind when we got on the interstate. We were all rolling along at highway speeds and he was over reving and going much slower than us. Now I know how he felt. Every once in a while I find myself pushing the shifter out of high gear thinking I have one more gear higher to shift into.

I see why so many people are putting 5 speeds behind even flatheads.

Don

Yep know what you mean Don, changed from 3.75's to 4.11's on my old 29 Coupe and regretted it, 4.11's are fine for the strip but a pain on the street.

Hey Don I can relate to the trying to find another gear out on the open road.A truck that I drove for work for 2 or so years I was always trying to find that next gear as I always drove with the go pedal resting up against the floor mat.

The TREMEC book has an easy formula for calculating cruise RPM and shift points: RPM = (mph x Differential Gear Ratio x 336 x OD Ratio)/Tire Diameter in Inches

The "336" is just a unit factor. For example, my '33 at (70mph x 4.11 x 336 x 0.64)/31 yields 1996 RPM. For shift points put in your individual tranny gear ratios in place of the OD ratio, like my shift points at 3000RPM are 23, 36, 53, 67 and it'll hit 105 in 5th. I built a little Excel spreadsheet when I was chasing my ratios - I can e-mail it to anyone that wants it, or there are lots of calculators on the web (forum does not allow Excel file attachments).

Hmmmm... I have to take issue with the TREMEC book. I can't figure out where they got the 336 figure. Using more conventional math methods with the numbers above (wheel diameter X pi, converted to feet per minute X gear ratio, etc, etc.) I come up with 3119 rpm @ 70 mph. When I figure it back the other way (1996 rpm/ 4.11 X tire circumference, etc, etc.) it comes out 44.8 mph.

I can post the rather lengthy process I used if anybody is interested. Meantime, can somebody else do the calculations and see which is correct?

Originally Posted by J. Robinson

Hmmmm... I have to take issue with the TREMEC book. I can't figure out where they got the 336 figure. Using more conventional math methods with the numbers above (wheel diameter X pi, converted to feet per minute X gear ratio, etc, etc.) I come up with 3119 rpm @ 70 mph. When I figure it back the other way (1996 rpm/ 4.11 X tire circumference, etc, etc.) it comes out 44.8 mph.

I can post the rather lengthy process I used if anybody is interested. Meantime, can somebody else do the calculations and see which is correct?

Multiply and divide the numbers as written - 70x4.11x336x.64 = 61,867.008 divided by 31 equals1,995.7 . The 336 figure takes pi plus all of the conversions of miles, feet, minutes, seconds, etc into account, and the numbers prove out by seat of the pants in the car. Trust me, I ran the dimensions and confirmed the 336 number before I used it....

The 336 comes from (5280ft/mi x 1hr/60min x 12in/ft) divided by pi to get the dimensions into RPM. Your 44.8 MPH is right, but neglects the final OD ratio of 0.64 - when you divide 44.8 by 0.64 you get 70MPH.

Here is a site I have used in the past and it makes it very simple to figure out your rpms. All you do is plug in your gear ratio (no periods or colons), your tire size and your intended speed, and it gives you the rpms for an automatic, aod, manual, and 5 speed transmission. It is very accurate, my tires on the 27 are about 29 inches tall and it pegged my rpms at 2984 and change. On the road I was turning 3,000 at 60 mph on the gps.

http://www.reiderracing.com/rtech-engine-rpm.php

Try this with your cars info and see how it compares.


I have been considering changing to Hurst brand slicks this time on the rpu, but they are a little short, only 28.75 tall, and the Firestones I had on my 23 were 30. That 1.25 makes a little difference, and also looks better IMO.

Don