Help selecting an "ideal" street rear end ratio

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77cruiser
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Re: Help selecting an "ideal" street rear end ratio

Post by 77cruiser » Sun Mar 06, 2016 12:35 pm

This guy can build you one to hold up. Do you race it with sticky tires?
http://www.extremeautomatics.com/th2004 ... 004RStage1
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Re: Help selecting an "ideal" street rear end ratio

Post by slowmobile » Mon Mar 07, 2016 10:16 am

Rizzle wrote:There is the possibility of using a universal bell housing TH350C if converter slippage is playing a large part in cruising rpm. Might also be possible to do a high stall/lockup to mimic a 6 speed (I've driven some older equipment which did the high stall/lockup, shift into converter, and lockup again to effectively double the trans gears) , with a slightly taller rear gear to noticeably drop the cruise rpm.
That is, if you can find a th350C converter with a strong enough lockup to take your high torque numbers...however, it should let you use the majority of your current go-fast trans parts.

Or, and probably the better idea, is the 4l85e.

What type of shifter/shift pattern do you currently have?
Converter slippage is contributing. I figure it to be about 8% at highway speeds based on what calculators tell me the RPM "should" be.

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Re: Help selecting an "ideal" street rear end ratio

Post by pdq67 » Mon Mar 07, 2016 8:19 pm

Back in HS, a classmate had a '56 98 Olds convert with 4-speed hydro in it. It went shift-shift ------shift-------shift! The big Olds convert must have weighed 5,500 pounds!! 324" engine powered...

Now, I want to say that Buick made "switch-pitch" converters back then that were in their big cars! Something like a decent drop in rpm if not mistaken..

I had a copy of the 1969 Mag with the 2-speed rear end article in it years ago.

And I think I e-mailed Autogear as well as MOSERS telling about the existence of it and asking them if they would build such a rear end to no avail.

All this said, If I wanted a bullet-proof 4-speed automatic, I would have "Jakeshoe" build me a full manual reverse shift 4L80 and be done with it. Or a real Art Carr 200-4r, but like Art said when I e-mailed him, it would be pricy to say the least..

I also like the Legend LGT-700 5-speed and I almost got down on my hands and knees and begged Autogear to finish their Muncie 5-speed and not the internal shift rail tranny, but like a real Muncie with a 5th OD gear in the tail-housing!

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Re: Help selecting an "ideal" street rear end ratio

Post by autogear » Tue Mar 08, 2016 9:24 am

Someone mentioned the Doug Nash Under/Overdrive (produced by US Gear). Its a great piece; but, just make sure you get the OVERDRIVE -NOT- the UNDERDRIVE.

The issue with a 2-spd rear from a niche market production standpoint is if we picked the Ford 9", the GM guys would have a cow, if we picked the 12-bolt, the guys with the 9...would have a cow, and the same with the Dana guys. Its also a huge tooling investment, unless an axle company was interested - and they're not.

Paul, your prayers have not fallen on deaf ears LOL

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Re: Help selecting an "ideal" street rear end ratio

Post by Dan Timberlake » Tue Mar 08, 2016 1:57 pm

Another period Magazine with a test of the 2 speed rear.
http://www.coverbrowser.com/image/rod-custom/147-4.jpg

I don't have that issue. Was just scanning the covers.

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Re: Help selecting an "ideal" street rear end ratio

Post by pdq67 » Wed Mar 09, 2016 12:14 am

autogear wrote:Someone mentioned the Doug Nash Under/Overdrive (produced by US Gear). Its a great piece; but, just make sure you get the OVERDRIVE -NOT- the UNDERDRIVE.

The issue with a 2-spd rear from a niche market production standpoint is if we picked the Ford 9", the GM guys would have a cow, if we picked the 12-bolt, the guys with the 9...would have a cow, and the same with the Dana guys. Its also a huge tooling investment, unless an axle company was interested - and they're not.

Paul, your prayers have not fallen on deaf ears LOL
Thanks Autogear, and I know they haven't.

If I had the money I would buy the blueprints from Ford and make it myself! Just like I would love to make a real Muncie 5-speed OD tranny!

pdq67

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Re: Help selecting an "ideal" street rear end ratio

Post by silver6767 » Fri Mar 25, 2016 8:33 am

Got a '67 Coronet with 3.54's and a 28" tire at the track and on the street. Pulls all of 3,200 RPM at about 68-69 mph. 65 mph is about 3,100.
505 BBM, solid flat tappet.
Car weighs 4,008.
9-1/2 convertor. 2.75 first gear.
Runs 11.50's and 11.60's @ 115-116.
Last year i put a touch under 1,700 miles on the street as well as occasionaly going rounds bracket racing.
Still breaks the tires loose at around 50 mph.
Spose it also boils down to what you can comprimise with.

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Re: Help selecting an "ideal" street rear end ratio

Post by peejay » Sat Mar 26, 2016 3:27 pm

autogear wrote:Someone mentioned the Doug Nash Under/Overdrive (produced by US Gear). Its a great piece; but, just make sure you get the OVERDRIVE -NOT- the UNDERDRIVE.

The issue with a 2-spd rear from a niche market production standpoint is if we picked the Ford 9", the GM guys would have a cow, if we picked the 12-bolt, the guys with the 9...would have a cow, and the same with the Dana guys. Its also a huge tooling investment, unless an axle company was interested - and they're not.

Paul, your prayers have not fallen on deaf ears LOL
If you picked a 9" then it would bolt in to existing rearend housings. Heck you might be able to bolt into existing carriers if it could be a cassette that replaced the pinion support.

Half the GM guys are running 9" rears anyway, who cares?

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