What is a jack shaft?

I’ve been reading some build threads trying to sus out the best way to sort the axles on my ej into l80 conversion. I’ve seen a few posts that refer to jack shafts and hybrid or equal length axles but my brain can’t quite figure out how these work.

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Best just to show you a pic there are 2 different types. I’m not familiar with the l80 front end so i don’t know wether this will bolt in, this is from the l5.

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To explain the one on the right in the Pic @601to602 has supplied the part closest to us goes in the gearbox and is the same splins as an inner cv joint, It gets held to where the engine mount is with bolts through those 2 holes so it cant move, It then has its own unique cv joint and the short shaft goes in there and the rest is the same as a normal cv shaft.

With your ej into your L80 you should be able to do it quite fine. Have a look at “ill minded” build thread through the daiforum link and you will see he just used his L80 gearbox etc on his and it was fine if keeping the smae standard hubs etc.

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One of the benefits of a jackshaft is (sort of) a reduction in torque steer. Think of them as torsion bars. They do get slightly wound up. A longer shaft can be wound further than a short shaft, given the same energy input (or can be wound further before it fail given increasing application of torque). Well the long shaft takes a tiny bit of drive away as it winds and then it releases. One side of the car has a slow and then fast drive compared to the other side. Perhaps not noticeable on a low power car but I’ve been in one Mira with 150hp plus at the wheels and it was critical having equal shafts. I was skeptical about all of this but over a few years association with that vehicle and seeing a couple of shafts break and how they broke - yeah they twist up.

The front wheel drive TRXX limited slip differential boxes have the clutches (or viscous) unit outside of the box and inside the fat part of the jackshaft. The four wheel drive TRXX boxes that I have seen (in pictures) use a front wheel drive box and have a jackshaft that sends power to the rear. You may think that means the drive comes form only one side. But, as with the front wheel drive lsd, the drive is balanced left to right with a regualr looking output shaft and a dog drive out put surrounding this (yes I should take some pics and insert).

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Here’s a couple of pic’s of the 4 wheel transfer case and tail shaft.

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Thanks guys. Turns out my imagination wasn’t far off. Would any of you know if there’s a vehicle with these that would suit an ej de and box out of an l701

You may need to be a bit more specific in what you are asking. I assume you want just a jackshaft that performs no other function other than allowing equal shafts. I’ve not seen on from factory on an Australian delivered vehicle. My two LSD ones are from TRXX half cuts (will prob end up for sale complete with gearbox at some point but won’t be cheap) and the other two more simple ones (one spoken for and the other not for sale) came off imported ef engines out of “I don’t know what”.

I believe they are from a Copen?? @evilhighway @601to602??

From the land of JP

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the 2nd one i got was on yahoo from an L6 or L5 im not sure which from memory

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The more you know!

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Not just a jackshaft but a clutch type LSD from an L200 TRXX
Sort of funky having the LSD on the outside. Not sure how it’d go circuit racing or rallying as it can’t have very good cooling. What on earth do they look like inside? I’m not curious to pull this one apart. Here’s the funk - drive comes out one the rhs of the gearbox into the splined shaft which seems to rigidly go out the otherside to the wheel. The clutches inside conect that shaft to the LHS drive via those big dog gears. Kinda kool.
I also have a viscous version which is in the car now. Note you must have the matching differential that has the requried dog engagement. And clutch type dog gears are diff size to vicous. So you can’t just swap these two units about. A lsd jackshaft change means gearbox change.

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The l5/6 tr-xx and sr-xx have these as optional, there was also a conventional clutch type lsd diff option for the l512s as being all wheel drive the transfer case bolts to the right hand side. Have seen a couple fitted to 2wd cars ie l502 x2 rally with a jack shaft. I’ll have a look for some pics.

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From 95 parts catalogue. I’ll try and find some pic’s i have /use to have of one fitted to a 2wd l502 case

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Pciture pinched from my build thread shows the Viscous lsd jack shaft mated to crownwheel and pinion for demonstration purposes. The jackshaft engine mount bracket on these is cast iron. On clutch type seen above they are alu and possibly forged.

@601to602 that diff centre appears to be a torsion torque sensing type base on how the gear sit. What do you know about this?

You may be right, something like the old Fuji torque-sensing lsd. but i have no pics of the mechanism as they are quite rare and difficult to find info on only pic i have at the moment is this one, although i’m still looking.

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you @601to602 my friend are the master of unearthing the rare and provider of tantilising knowledge.

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Ok found pic of the mechanism.

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I have this on the way from japan for the move it only cost me 2000yen, i already have the axles and i intend to have the diff machined to take the dog gear teeth i believe this is possible?

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Hmm, I would have to have a look at my diff. Bit dark to open up the shed at the moment. If you need pics and I forget, please remind me. Your pic looks like my clutch type. If I didn’t have one I, like you, would be after this more so than any other option. I’ve signed out of all Daihtasu Facebook stuff except that Sirion Rally one you did show us. The conversations on most of those pages are just not for me. At the root of my pain listening in is the talk of “big boost” and so on. My EJ-DE na powered L200 will light up the tires in first and second with reasonable rubber. Both tires. How on earth do these “big boost” guys get any forward motion with their open diffs? Handling too, how do you get through a corner without lighting up the inside tire when no LSD? I have never ever sought to progress a project without diff control. On the other hand I guess some people have never tried one. With and without in my car it was like night and day and I could never go back.

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