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JDM tranny theory

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Black_Havoc

15+ Year Contributor
83
0
Aug 17, 2003
Beaverton, Oregon
Ok, I have a theory here. It needs some input, and some detailed photos, and diagrams. On the JDM T/F case, it has a pin you pull to convert to FWD. I assume its incase you strip off the teeth from the center or rear diffs. However, thinking about it, I could fabricate some selonoid, to pull that pin after the clutch is depressed and shifter is in the 3rd gear position. Hence, you would get the AWD start, and the FWD top end. Is it possible? How does the pin interface with the T/F case? It would also not re-insert the pin untill the VSS sent no signal, thus being 0 MPH. I need info people, anyone with a diagram of the JDM t/f case, or anyone has one sitting around, could dissasemble it and take some photos. Any help here would be awesome. This would be the ultimate mod for the tranny ever, if it would work reliably.
 
Sorry I dont have any info but that would be awesome. Kinda like a truck with selectable 4WD. Id reccomend PMing GRNDSM since he is very knowledgeable in this type of stuff.
Moises..
 
Personally I don't think it would work all that well. I'm not tryin' to say it can't/won't - but is it worth the time & money? And correct me if I'm wrong but isn't the reason that the FWD's pull on top end is because they have less rotational mass/less weight. If you do start this 'project' keep us updated.

*How would you be able to swith from AWD --> FWD when the car is moving?
 
Wait a minute, I thought all the hype from being AWD and losing topend was becuase your carrying deadweight after the luanch becuase of the extra rearend mechanics. So what would making it fwd do besides freeing up a little drivtrain loss, or is that all your trying to acomplish, getting rid of the drivetrain loss? Just seems like a lotta work for a little horsepower IMO
 
Sounds like a good idea... there is one problem tho. Instead of having to use extra power to spin all of that extra weight, You will STILL loose power because it all still spins when you're going down the road. All of that stuff is connected though the tires/axles/rear dif/driveshaft... It will still drag the car down just as much.
 
---Wait a minute, I thought all the hype from being AWD and losing topend was becuase your carrying deadweight after the luanch becuase of the extra rearend mechanics. So what would making it fwd do besides freeing up a little drivtrain loss, or is that all your trying to acomplish, getting rid of the drivetrain loss? Just seems like a lotta work for a little horsepower IMO---


Rotating mass powered by the engine is what I'm eliminating. Once the rear end is "turned off" it becomes unpowered rotating mass. Maybe a few HP are used to pull it, instead of 15 to turn it. FWD cars typically have driveline loss of 10-20%, AWD cars 20-30%. If I can free up that extra 15 HP thats enough to get me in almost a half seccond faster.

I'm still looking for diagrams on how the pin release system works. I know it has something to do with the center diff. Or maybe its like the steering wheel lock, a star plate that the pin engages into. I need more info before I can even attempt to pull it at speed. If i can find a used JDM T/F case for under 80 bucks, I'll give it a whirl.

At first I'll have a passenger yank a cable when I shift out of 2nd, on the way to 3rd. Then if it works, I'll progressivly get harder on it till I'm all out racing. If it holds, then I'll get an electric servo, and a switch on the select and shift arms, that will let it release in the 2-3 shift, but not push it back till its in 1st again. If it works, its going to be freaking awesome. Picking up 15 HP is like turning the boost from 11 to ~15. So if your running at 15PSI, and gain another 15, its -=like=- an instant 4PSI increase, though no more pressure is being induced.

15HP makes a big difference, I also have a Fiero, with a 2.5L I-4. HTey have 98 whole HP stock. WIth the mods I've done, its around 115 (17HP gain). Thats a great gain for a POS, pushrod, 2 valve, throttle body injected, 5400 RPM limited motor, with barley enough torque to turn the tranny ;-). I continually beat early 90's Integra's over and over. And they are supposed to have somewhere around 130HP. True my Fiero is lighter, but before the mods they were beating me. I'm just rambling now, too tired. later all.
 
You may Gain horsepower on a traditional dyno, BUT thoes drivetrain components that you previously SPUN will still have to SPIN... so whats going on is you're trading more drag on the motor FOR a little more horsepower. The physics of it state no gain in speed. Worst case scenario - your load is increased because you have to pull all of thoes rear end parts instead of have them spin with the transmissions power. When you increase your load, your timing will go down, causing you to have less horsepower in the top end. I dont see any gain or loss of speed with this 'mod'. just my .02
 
just for instance: a big jacked up bronco has selectable 4WD.... you have IN/OUT which controlls the output to the front axle. This is all fine and dandy but the entire rotating assymbly in the front end STILL moves... this is why trucks have lockout hubs. when you take the vehicle OUT, you also unlock the hubs - this disables ALL of the axle shafts, front dif, front driveshaft, intermediate shaft in the x-case. If you dont unlock the hubs - ALL of these parts still spin and cause drag. The only way that you could make your car FASTER with a selectable transmission would be to unlock both the transmission/transfercase and AND have lockout hubs on the wheels so you could disconnect them from the rear axles.

By the way, the selectable case has a pin in the x-case AND a pin in the transmission. For info: check this out.

good ol VFAQ to the rescue

http://www.vfaq.com/mods/Tranny-switchable.html
 
I would recomend checking the early 90s stuff, alot of vehicles had air powered locking hubs.
 
Guys,

I have been using JDM switchable transfer case for a over 3 years now and I have given it a considerable thought. There are two problems with using a solenoid:

1. You need a lot of force (~8-10lbs). You can get it with 12v, but it would take pretty large solenoid to make such force. Plus, most solenoids will have a problem getting you that much force for the entire stroke of ~.6".

2. Your default condition will be FWD. So if solenoid ever fails, you will be stuck in FWD until you jack up the car and manually override it. I can not afford to lose a race because of this... And believe me, you will most races if your all of the sudden turns into a FWD :).

You can use an extra spring and make 4x4 mode as your default, but can you imagine what would happen to you if this solenoid fails on a FWD dyno at 130mph wheel speed?

For all of these reasons, I have decided to create a manual cable actuation system. I should have all the parts ready in a couple of month.

The thing is that I am not sure just useful this would be. The #1 use that I can think of would be to do a FWD burn out and warm up your tires before a race. I guess I will find out this year if this is a useful feature :). At this point, I am not 100% sure if I want to mass produce it.

I suppose you can also use it to get FWD for 2WD dyno usage, but that is something that can be done now in just a couple of minutes.

As for getting rid of parasitic RWD losses, most people have came with only around 10hp attributed to the RWD (FWD/AWD dyno testing). So that is not a major consideration. Sill, I am planning on making such experiment at the drag strip (switching into FWD in 4th gear). My prediction is that I might pick-up 1-2mph in trap speed, but with out much impact on the actual ET.

Leon
RR
 
ok i dont know if you all have said this or not because i got tired of reading. i think what you saying could work if what youre saying is that you plan on disengauging the driveshaft from the T-case. if so the motor wouldnt have to turn the rear shaft at all, there for freeing up hp and not losing anything. you could you put a "pin" at both ends of the driveshaft and pull it, disengauging the drive shaft completely, not just from the T-case. that way it would free alot and it wouldnt turn the shaft. im sure that would help some. but im really not sure what the hell it would do because im not a drivetrain guy. why couldnt you like rig up a selectable t-case from a truck or something and make it work. and if <---thats a big "if" theres one in the jdm spec cars why couldnt you just get one of those and hook it up to work in our cars? and if there is one, could it be out of and mitsu. etc. car or truck with a 1.8 or 2.0 fo banga thats awd or 4x4? just my 2 cents

later
JJ
 
>if <---thats a big "if" theres one in the jdm spec cars why couldnt
>you just get one of those and hook it up to work in our cars?

You really should read the thread BEFORE you reply to it…

Such transfer does exist… And that is what we are talking about here… I started my post, right before yours, stating that I have been using one for several years!

Leon
RR
 
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