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Techical Discussions => Tech- - DRIVE TRAIN => Topic started by: Anthony Prescott on September 20, 2010, 09:32:54 AM

Title: manual overdrive??
Post by: Anthony Prescott on September 20, 2010, 09:32:54 AM
id there an o/d box that you can put in line behind your trans? almost like a divorced box? or can i turn around a divorced transfer case to reverse the hi/low range to give me that overdrive? 2 questions....(http://www.moparfins.com/forum/smileys/smiley7.gif)
Title: manual overdrive??
Post by: Steve on September 20, 2010, 10:26:49 AM
The problem with the transfer case is you won't be able to shift it on the fly.  Most of the transfer cases are engaged all the time.  When you shift into 4 wheel, as an example, you are actually engaging the front axle.  The older lever type were lever controlled, but real difficult to shift, especially while moving.
 
I remember my 84 Ram Charger was a real pain to shift at higher speeds, but at lower speeds it was OK
 
As far as the external overdrive is concerned, it seems to me I saw one still in production a few years ago.  But don't remember who it was.  It was a kit requiring you to supply all the info on the wheelbase.  As I recall, it was electric shift with a vacuum switch that disengaged it when you accellerated hard.  You'll have to look around in Google
Title: manual overdrive??
Post by: Guests on September 20, 2010, 10:49:10 AM
Trying to complicate the original plan that much more? Thing is, for what you are trying to do, getting a five speed transmission to do what you want is cheaper and have proven themselves to do what you are looking for instead of trying to reinvent the wheel. A 4.10 rear end will meet almost all the needs you can have in the T-18 towing/pulling capacity, whereas a five speed with a .75 overdrive will get those gears into the 3.02:1 highway drive capability for a lot less time, hassle and fabrication of any other overdrive unit.
Title: manual overdrive??
Post by: Rich on September 20, 2010, 10:52:37 AM
 It would be so nice if those OD's were still available:
 I had a '55 Dodge Custom Royal with the little 270" Red Ram Hemi backed up by a three on the tree with overdrive. The OD worked in all the gears and was electo/vacuum operated (it had a governor sticking out the side). There was a Lever on the dash that you slid down into OD position (cable connected to the OD unit), then all you had to do was go above 30 mph, let off the gas pedal and it would shift into OD - I could go 60 mph in 1st gear! Second gear was good for almost 100 mph. All you had to do to kick the OD off was to floor it quickly and it would shift back into regular mode.  


Title: manual overdrive??
Post by: Steve on September 20, 2010, 11:05:27 AM
Quote from: dana44
Trying to complicate the original plan that much more? Thing is, for what you are trying to do, getting a five speed transmission to do what you want is cheaper and have proven themselves to do what you are looking for instead of trying to reinvent the wheel. A 4.10 rear end will meet almost all the needs you can have in the T-18 towing/pulling capacity, whereas a five speed with a .75 overdrive will get those gears into the 3.02:1 highway drive capability for a lot less time, hassle and fabrication of any other overdrive unit.


 
True
 
Check out Kiesler Transmissions.  Bolt in and forget it
Title: manual overdrive??
Post by: Guests on September 20, 2010, 01:10:12 PM
Keisler is the way to go, but they get pretty pricey over the long run. I am thinking Dodge truck, or even behind a diesel five speed manual to fix the problem, which could actually be well under a grand and as little as a couple hundred, Keislers get above $2000 and GearVendors are above that.
 
Time to get on Craigslist around your area and see if you can find a truck manual five speed, your adapter from big block to small block will work.
Title: manual overdrive??
Post by: Steve on September 20, 2010, 01:24:59 PM
He needs a 518 from 1988 to 94 from a 2 wheel drive.  You can't use the later 518 unless you can convert the governors over to mechanical.


 
There is a big block adaptor for the 518.  You have to cut the bell off the 518 and the adaptor bolts on through the front pump somehow.  Sounds kind of crude, but is racing certified
Title: manual overdrive??
Post by: Anthony Prescott on September 20, 2010, 03:02:58 PM
this deisel 5 speed have a granny gear? is there a chance there's an adaptor made for the big block?? getting tired of casting new parts. 
Title: manual overdrive??
Post by: Anthony Prescott on September 20, 2010, 03:09:07 PM
OK>>>>> scratch that... new question.. can you run a regular truck 4 speed backwards? ya know... behind the first one?   two transmissions? my thought is that it'll give you 16 foreward gears, some equal to others of course. is it possible if i support the input shaft with a bracket so it doesnt wear itself down?, and can it shift in the oppisite direction? i also have to factor in that putting it in neutral only disengages the input shaft. or does it? i know i'm complecating things, but its curiosity getting the best of me.
Title: manual overdrive??
Post by: Steve on September 20, 2010, 03:25:36 PM
too much engineering and fabrication
 
Why do you need such a low gear?
Title: manual overdrive??
Post by: Snotty on September 20, 2010, 06:41:43 PM
He said something about a hill he has to climb up and down in his other post.
 
The NP208 Transfer case was designed for shift-on-the-fly.  It works well but I think it requires automatic front hubs.  I knew some people in Sierra County who coinverted the front hubs to manual because they wanted to be able to shift into low (must be stopped) without locking the front wheels.  You can shift into 4 Hi from 2WD or from Lo without stopping with that case.
Title: manual overdrive??
Post by: Anthony Prescott on September 20, 2010, 07:12:43 PM
ok all good stuff.... on another note, I was talking to my dad today and he remembers an overdrive component that bolts up between the engine and the bell housing. he doesn't remember who makes it, or if it's electric or manually controlled, but he says he used to install them when he worked for a tranny shop many years ago. does anybody know what i'm talking about? 
Title: manual overdrive??
Post by: Anthony Prescott on September 20, 2010, 07:15:23 PM
oh, and the dual tranny thing, its not for the low gear. its for the high gear. the 2nd tranny is trned around so the input shaft is facing the rear axle. info on this make shift aplication is appreciated as well. thanks in advance.
Title: manual overdrive??
Post by: Guests on September 20, 2010, 07:25:32 PM
ONce again, yes, if you have the money the parts are out there. If you do the two transmissions, again, you are getting into a lot of extra fabrication and cost, and reality is to take the second transmission and turn it backwards, using fourth gear to give you your 1:1 drive, third gives you whatever gear reduction in order to get overdrive. For example, if the third gear is 1.5 (to figure simple math quicker), you would then have a 1:1.50 ratio (and if the rear was 4.10) to give you a 2.73 overdrive to the rear end, run it the other way and your third gear would be 6.16 gear in the rear. Essentially you could walk faster than the truck could rev in first/first and 4.10,  so in essence all the work of setting up the second clutch hydraulically and building a cage and large tapered bearing to handle the clutch pressure bolted to the front side of the second transmission is a heck of a lot of work  and then you have to worry about the amount of truck bed and stuff you would be losing in the transmission hump to fit. A two speed rear end, even shortened, would probably be cheaper.
 
Are you trying to get  overdrive or underdrive?
Title: manual overdrive??
Post by: Steve on September 20, 2010, 07:30:32 PM
Quote from: Snotty
He said something about a hill he has to climb up and down in his other post.
 

Yeah that's the one I was talking about.
 
I forget how that operated.  I just remember it took quite a tug to get it into 4 wheel high or low.
Title: manual overdrive??
Post by: Guests 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?
Title: manual overdrive??
Post by: Steve 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
Title: manual overdrive??
Post by: Anthony Prescott 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?
Title: manual overdrive??
Post by: Anthony Prescott 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.
Title: manual overdrive??
Post by: Anthony Prescott 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. 
Title: manual overdrive??
Post by: Anthony Prescott on September 20, 2010, 08:58:22 PM
disregard the 1:52 am comment
Title: manual overdrive??
Post by: Anthony Prescott on September 20, 2010, 08:59:21 PM
that only applies with the use of a 5 speed as secondary.
Title: manual overdrive??
Post by: Brian 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.