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Author Topic: manual overdrive??  (Read 1234 times)

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manual overdrive??
« Reply #15 on: September 20, 2010, 07:49:52 PM »

At this point, I have basically completely been sideswiped with new, extra, other questions that I have decided it is time to know what the parameters of what needs to be accomplished so we can really figure out what is wanted instead of trying to answer hypotheticals for a person that probably has less money than I do, putting 90percent of the answers out of the ballpark from becoming a reality.
 
With that, here is a simple description of a 4spd to 4spd would be geared in simplicity.
 
1st 4:1
2nd 3:1
3rd 2:1
4th 1:1
 
Second transmission the same
Rear end 4.0:1 for simplicity
1st to 1st to rear end would be 4:1 times 4:1 times 4.0:1 or 64.0:1 ratio at the rear wheels.
2nd to 1st would be 3:1 times 4:1 times 4.0:1 ratio to the rear wheels as 48:1
3rd to 1st would be 2:1 times 4:1 times 4.0:1 which is 32:1
4th to 1st would be 1:1 times 4:1 times 3.0:1 which is 12:1 rear end ratio to the tires.
 
first to second would be 4:1 times 3:1 times 4.0:1 or 48:1
second to second would be 3:1 times 3:1 times 4.0 or 36:1 to the tires.
 
4th to 4th would be 1:1 times 1:1 times 4.0:1 or a true 1:1 ratio
 
So, as you can see, fill in the rest of the blanks and a normal granny four speed is around 4:1 times 4.0:1 rear or 16:1, and this is good for about 15miles per hour at redline, so look how granny geared this would be overall.
 
Now, again, what are you trying to accomplish as the main question?
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Steve

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manual overdrive??
« Reply #16 on: September 20, 2010, 08:05:31 PM »

Somewhere he said something about 7,000 pounds towing.
 
That's not much at all.  I just ran through the rockies with 8 bushel in tow and another bushel on the truck.  So I was somewhere around 16,500 total.  I run with 4.42 gears, and 285-17's on an automatic.  I even got trapped on a mountain highway that was all dirt because they were improving the whole road.  Got the bottom of the trailer caught twice too.  But pulled it right out.  Popped the tail lights out on the second one.  I may as well been off roading
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Anthony Prescott

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manual overdrive??
« Reply #17 on: September 20, 2010, 08:48:03 PM »

why would i need a second clutch? the primary clutch would disengage both transmissions. it would be the best of low gear and overdrive gears. would the output being disengaged be the same as the input shaft being disengaged? i guess my question is will it shift?
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Anthony Prescott

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manual overdrive??
« Reply #18 on: September 20, 2010, 08:52:10 PM »

the overdrive capability AND the low end is what i'm after. if the 2nd tranny is backwards, i would have 6 overdrive gears. and under drive would be intense.
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Anthony Prescott

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manual overdrive??
« Reply #19 on: September 20, 2010, 08:57:35 PM »

ex... 1st tranny in 1st gear and the 2nd tranny in 4th is a crawler gear. no different than 1st gear alone.. BUT.... 4th gear on the first tranny and 1st, 2nd, 3rd gear on the second tranny would be a tremendous overdrive option. 
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Anthony Prescott

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manual overdrive??
« Reply #20 on: September 20, 2010, 08:58:22 PM »

disregard the 1:52 am comment
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manual overdrive??
« Reply #21 on: September 20, 2010, 08:59:21 PM »

that only applies with the use of a 5 speed as secondary.
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Brian

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« Reply #22 on: September 21, 2010, 10:22:02 AM »

I agree with the others, some neat ideas but tons of engineering involved.  If you can fab your own hardware then you might come out ahead.  But I doubt it.

The truck trannies you would need to use would all be internal shift as well.  So the second tranny shifter would be in the back of the box, if it was a regular cab, and in the back seat if it was a crew cab. Or you would need to fab up one heck of a shift rod system to be able to row the gears in the second tranny.  Also the drive shaft angle from the second tranny on down to your differential would be extreme as well.

The gear vendors OD unit would be far cheaper, easier, and more reliable in the long run.


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Brian

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