Hello, I'm building a kit car with a subaru drivetrain. the car is a mid-engine awd of my own design built on a composite monocoque body. I'm trying to figure out the best way to get the power up to the front wheels. I've flipped the rear differential up side down to keep the same rotation. I was thinking about using a suzuki sidekick transfer case because they have a 1:1 high gear ratio. I would use the 4 wheel hi mode on the transfer case to utilize the forward output. My question is would the transfer case incur damage like they can in 4x4 vehicles if driven on dry pavement? I would think the transfer case wouldn't feel anything because of the viscus clutch in the suby tranny. Please correct me if I'm wrong on that theory. I can't find much info on the transfer case so I though I'd see if there were any off roaders on here who knew anything. Thank you very much.
Casey
Transfer case hooked to tranny rear output?
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AWD_addict
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Welcome to the board! That sounds like a fun project. I made a rough design of a subaru-powered mid-engine for a class project. I avoided completely working out this problem though.
You probably want to ask some suzuki guys if that transfer case can handle what you want. The center diff in the subie transmission should take care of the front/rear wheel speeds issue, just as it does normally.
How are you going to package the driveshaft to the (now) front diff? Just outboard the exhaust manifold or under a custom oilpan were my choices.
You probably want to ask some suzuki guys if that transfer case can handle what you want. The center diff in the subie transmission should take care of the front/rear wheel speeds issue, just as it does normally.
How are you going to package the driveshaft to the (now) front diff? Just outboard the exhaust manifold or under a custom oilpan were my choices.
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vrg3
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I'm not sure I understand...
You're trying to build an AWD kit car with mostly Subaru drivetrain parts? A Subaru engine mounted backwards midship?
So what used to be the rear driveshaft is now the front driveshaft.
But now you're trying to figure out how to power the rear wheels? And you're thinking a Sidekick transfer case stuck in the middle of that driveshaft will allow you to physically transfer power to another differential in the rear?
What are you going to do with the stock Subaru front drivetrain? The Subaru gearbox has a center differential at its tail end. That differential has a viscous coupling in it to limit slip, yes. The rear output goes out the back of the center diff, and the front output goes out the front to the front differential built into the transmission.
The viscous LSD doesn't fully lock and will quickly shred its silicone goo if continuously driven with mismatching speeds.
People have done RWD conversions on Subarus, either by welding the center differential and removing the front axles, or by replacing the center differential with one designed to send power only rearward.
So maybe you could do that to the center diff. But then, yes, you would have to worry about torque bind with the Suzuki transfer case, because you'd have no center differential at all.
You're trying to build an AWD kit car with mostly Subaru drivetrain parts? A Subaru engine mounted backwards midship?
So what used to be the rear driveshaft is now the front driveshaft.
But now you're trying to figure out how to power the rear wheels? And you're thinking a Sidekick transfer case stuck in the middle of that driveshaft will allow you to physically transfer power to another differential in the rear?
What are you going to do with the stock Subaru front drivetrain? The Subaru gearbox has a center differential at its tail end. That differential has a viscous coupling in it to limit slip, yes. The rear output goes out the back of the center diff, and the front output goes out the front to the front differential built into the transmission.
The viscous LSD doesn't fully lock and will quickly shred its silicone goo if continuously driven with mismatching speeds.
People have done RWD conversions on Subarus, either by welding the center differential and removing the front axles, or by replacing the center differential with one designed to send power only rearward.
So maybe you could do that to the center diff. But then, yes, you would have to worry about torque bind with the Suzuki transfer case, because you'd have no center differential at all.
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TheSubaruJunkie
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The rear output of the Subie trans will make no difference, the problem will be with the Suzuki Transfercase.
It has no center diff, and its only job is to split power 50/50 front and rear. If you plan on using BOTH output shafts of the transfercase, then YES you will have problems with binding. The Subaru Diff will not help.
If you do plan on running a divorced transfercase behind a subaru transmission, you will need to weld the subaru's center diff or replace it like VRG indicated or else you will burn out the clutch packs in the diff and render your car useless.
Sounds like a fun project.
-Brian
It has no center diff, and its only job is to split power 50/50 front and rear. If you plan on using BOTH output shafts of the transfercase, then YES you will have problems with binding. The Subaru Diff will not help.
If you do plan on running a divorced transfercase behind a subaru transmission, you will need to weld the subaru's center diff or replace it like VRG indicated or else you will burn out the clutch packs in the diff and render your car useless.
Sounds like a fun project.
-Brian
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evolutionmovement
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So it sounds like from the front of the car to the back:
[rear diff] - [front driveshaft] -----------
----------------------------------------------|
[engine] - [AWD trans] - [Suzuki t/c] --
Aside from whether the t/c can handle the power, I'm curious as to your routing as well. I was thinking of something similar with a front mid-engined 3-wheeler with a single rear. I didn't like the weight and reliability unknowns, but the main issue was that I would likely have to raise the engine to pass the driveshaft underneath, ruining the CG. A custom pan is an option, but that means either dry-sump ($$) or wings off the oil pan to accommodate the necessary oil capacity and then may interfere with the engine mounts.
[rear diff] - [front driveshaft] -----------
----------------------------------------------|
[engine] - [AWD trans] - [Suzuki t/c] --
Aside from whether the t/c can handle the power, I'm curious as to your routing as well. I was thinking of something similar with a front mid-engined 3-wheeler with a single rear. I didn't like the weight and reliability unknowns, but the main issue was that I would likely have to raise the engine to pass the driveshaft underneath, ruining the CG. A custom pan is an option, but that means either dry-sump ($$) or wings off the oil pan to accommodate the necessary oil capacity and then may interfere with the engine mounts.
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I also have toyed with this idea. Alot.
My personal conclusion was that the added weight and effort can easily be negated by a properly engineered 2 wheel drive setup.
Look at the Elise. Do you think adding AWD would in any way improve that car? A Subaru mid-engined, but 2wd, car has the potential to blow away an Elise.
My personal conclusion was that the added weight and effort can easily be negated by a properly engineered 2 wheel drive setup.
Look at the Elise. Do you think adding AWD would in any way improve that car? A Subaru mid-engined, but 2wd, car has the potential to blow away an Elise.
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'93 Pure White SS EJ20G slanty intercooled, SIDESWIPED! In stasis.
'94 FWD and '95 AWD Laguna Blue SVXs.
2017 Pure Red BRZ Limited w/Performance pack
I'm thinking that in a light (fiberglass bodied) kit car that the Subie FWD engine/trans setup mounted midship would give outstanding handling and performance, probably on par with most Porsche's, without the hassles of trying to route power back to the front wheels. Turbo would just add to the permenant grin factor.
IF I were looking at an AWD mid engine I'd look at using the Suzuki T-case mounted on the center diff output to transfer power to the front diff (basically a U drive box). You'd still need the Subie center diff to control power transfer. You could even take out the low range gearing from the T-case to save weight and rotating mass. Leaving the 2 hi option could allow driving in rwd only using the FWD fuse circuit (set up on a toggle switch, even), if needed.
I'd look at routing the driveshaft alongside the oil pan diagonally forward to the front (inverted rear) diff. With the length of the shaft (from behind the rear wheels to the front diff, wow) the offset from the T-case to the diff would be minumal, but SHOULD still clear the oil pan. It could make the exhaust interesting on that side though.
My $.03 worth....
IF I were looking at an AWD mid engine I'd look at using the Suzuki T-case mounted on the center diff output to transfer power to the front diff (basically a U drive box). You'd still need the Subie center diff to control power transfer. You could even take out the low range gearing from the T-case to save weight and rotating mass. Leaving the 2 hi option could allow driving in rwd only using the FWD fuse circuit (set up on a toggle switch, even), if needed.
I'd look at routing the driveshaft alongside the oil pan diagonally forward to the front (inverted rear) diff. With the length of the shaft (from behind the rear wheels to the front diff, wow) the offset from the T-case to the diff would be minumal, but SHOULD still clear the oil pan. It could make the exhaust interesting on that side though.
My $.03 worth....
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evolutionmovement
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You have a problem with the driveshaft angle, then. Clearing the oil pan isn't the only issue - there's the engine mounts and exhaust as well. Length can be helped by bearing blocks (likely making servicing a PITA), but the angle would have to be pretty large to clear past everything from the short distance to the transfer case. You would have to use CV axles, without doubt, and even then, the angle will shorten their life and how much power are we talking?
I'd also hope you wouldn't have some of the problems Lamborghini has had with their AWD junk suddenly kicking sideways 90 degrees with sometimes deadly consequences (Diablo, Murcielago, and it seems Gallardo). (The factory won't officially acknowledge the problem so the cause isn't conclusive, however, it's likely a differential failure which wouldn't likely be a problem using properly made Subaru gear.)
The OSCA 2500 GT was a mid-engined light-weight fwd Subaru-powered concept that would have been awesome, but never got built.
I'd also hope you wouldn't have some of the problems Lamborghini has had with their AWD junk suddenly kicking sideways 90 degrees with sometimes deadly consequences (Diablo, Murcielago, and it seems Gallardo). (The factory won't officially acknowledge the problem so the cause isn't conclusive, however, it's likely a differential failure which wouldn't likely be a problem using properly made Subaru gear.)
The OSCA 2500 GT was a mid-engined light-weight fwd Subaru-powered concept that would have been awesome, but never got built.
Midnight in a Perfect World on Amazon or order anywhere. The first book in a quartet chronicling the rise of a man from angry criminal to philanthropist. Midnight... is a distopic noirish novel featuring 'Duchess', a modified 1990 Subaru Legacy wagon.
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All_talk
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I also have had some thoughts along these lines, I’ve even started some preliminary drawings. My setup would likely use a custom machined transfer case to replace the tail housing on the Subie trans with a “silent chain” transfer drive.
First question, Auto or 5 speed? In the Subaru the two AWD systems work differently and this may affect how you attack the power transfer. The Auto is much like most other manufactures, it is essentially a FWD trans with a variable clutch pack transferring power to the rear as the computer dictates. Note that the duty solenoid works opposite of what you might think… full 12V opens the clutch, open circuit locks the clutch. The 5 speed has a true gear type center diff with a VLSD across it. You get a four wheel torque balance up to the point of wheel slip, then the VLSD comes in. Because of the gear diff and 2-way action of the VLSD you get balance in both acceleration and deceleration, unlike many “transfer clutch” system that can decouple the rear on decal and upset the balance of the car when driving near the limits.
My plan would run a two piece drive shaft, the first being a solid CV type shaft run between the oil pan and exhaust port, second section would be the hollow style but might have CV style joints.
You might also consider using a Nissan truck R160 front diff unit, this would avoid the lubrication issues caused by inverting the (now) front diff.
Gary
First question, Auto or 5 speed? In the Subaru the two AWD systems work differently and this may affect how you attack the power transfer. The Auto is much like most other manufactures, it is essentially a FWD trans with a variable clutch pack transferring power to the rear as the computer dictates. Note that the duty solenoid works opposite of what you might think… full 12V opens the clutch, open circuit locks the clutch. The 5 speed has a true gear type center diff with a VLSD across it. You get a four wheel torque balance up to the point of wheel slip, then the VLSD comes in. Because of the gear diff and 2-way action of the VLSD you get balance in both acceleration and deceleration, unlike many “transfer clutch” system that can decouple the rear on decal and upset the balance of the car when driving near the limits.
My plan would run a two piece drive shaft, the first being a solid CV type shaft run between the oil pan and exhaust port, second section would be the hollow style but might have CV style joints.
You might also consider using a Nissan truck R160 front diff unit, this would avoid the lubrication issues caused by inverting the (now) front diff.
Gary
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evolutionmovement
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What about the motor mounts? Solid mount to some kind of overhead crossmember so that the axle could pass through that space?
I also considered a chain deal at one point on the three wheeler (more for a final drive change than anything) ahead of the rear swingarm, one end off the driveshaft from the transmission, the other on the shaft for the rear drive. In my case, it would have been compact, but in this case, you could extend the chain out fairly wide as necessary to run the shaft where you want it and eliminate the need for the t/c. Perhaps two identical motorcycle chain rings for a 1:1. The drivetrain would have to be rigid mounted, I would think, to keep the chain from coming off.
I also considered a chain deal at one point on the three wheeler (more for a final drive change than anything) ahead of the rear swingarm, one end off the driveshaft from the transmission, the other on the shaft for the rear drive. In my case, it would have been compact, but in this case, you could extend the chain out fairly wide as necessary to run the shaft where you want it and eliminate the need for the t/c. Perhaps two identical motorcycle chain rings for a 1:1. The drivetrain would have to be rigid mounted, I would think, to keep the chain from coming off.
Midnight in a Perfect World on Amazon or order anywhere. The first book in a quartet chronicling the rise of a man from angry criminal to philanthropist. Midnight... is a distopic noirish novel featuring 'Duchess', a modified 1990 Subaru Legacy wagon.
What is the offset for the Suzuki T-case, both out and down?
AND we are talking mid-engine and not a complete flip to rear engine, right?
If rear engine get the drivetrain from a Vanagon AWD, cut the driveshaft to length and mount everything.... Done.
Mid-engine the 'zuki t-case would be better than an open chain drive, IMHO, depending on where it positions the shaft. Exhaust is going to have to be custom anyway, so detouring around the shaft shouldn't be a huge problem, and engine mounts can be fabbed to go under, over, or around the shaft also.
Drive shaft angle, measured front to rear, even if using a 2 piece shaft, would not be significant enough to cause major problems. I assume we are looking at a shaft length of around 6' minimum with an offset in the back of maybe 12" off center. lifted 4x4's run much more angle than that.... The trans tunnel might look a little strange though.
AND we are talking mid-engine and not a complete flip to rear engine, right?
If rear engine get the drivetrain from a Vanagon AWD, cut the driveshaft to length and mount everything.... Done.
Mid-engine the 'zuki t-case would be better than an open chain drive, IMHO, depending on where it positions the shaft. Exhaust is going to have to be custom anyway, so detouring around the shaft shouldn't be a huge problem, and engine mounts can be fabbed to go under, over, or around the shaft also.
Drive shaft angle, measured front to rear, even if using a 2 piece shaft, would not be significant enough to cause major problems. I assume we are looking at a shaft length of around 6' minimum with an offset in the back of maybe 12" off center. lifted 4x4's run much more angle than that.... The trans tunnel might look a little strange though.
'90 Bermuda Blue L Wagon (Wife's),
Auto, AWD, Now with 275K + miles!
2005 Outback, 2.5 AWD (wife's new daily)
Auto, AWD, Now with 275K + miles!
2005 Outback, 2.5 AWD (wife's new daily)
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evolutionmovement
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You're talking about dumping it low either losing ground clearance or raising the CG so the engine could clear. There's only so far below the head you can go without either issue. As for motor mounts, an overhead frame that comes down and runs some metal across under the engine for it to mount to would get you more clearance, but you're running everything very close. That's assuming the t/c puts the output very close to centerline as well. Distance off center is important.
Chains can be used to transfer almost any power. A dual chain setup could be utilized with little extra effort if necessary. If it could be enclosed to keep it clean and mounted so that the transmission chain ring didn't move relative to the driveshaft chain ring, I think you'd have better potential reliability than a modified old t/c off a low-powered vehicle. With a shaft, the less angle you can run, the better for reliability and efficiency. The ideal would be to run it straight and only use the joints to account for flexing during driving. The chain set up allows you to put it wherever you want and doesn't force as many compromises with other systems (like the frame design, motor mounting, exhaust, etc.). I don't think you'd have a traditional transmission tunnel, more a shallow tunnel under the passenger (or driver's, preferably the passenger) seat.
Chains can be used to transfer almost any power. A dual chain setup could be utilized with little extra effort if necessary. If it could be enclosed to keep it clean and mounted so that the transmission chain ring didn't move relative to the driveshaft chain ring, I think you'd have better potential reliability than a modified old t/c off a low-powered vehicle. With a shaft, the less angle you can run, the better for reliability and efficiency. The ideal would be to run it straight and only use the joints to account for flexing during driving. The chain set up allows you to put it wherever you want and doesn't force as many compromises with other systems (like the frame design, motor mounting, exhaust, etc.). I don't think you'd have a traditional transmission tunnel, more a shallow tunnel under the passenger (or driver's, preferably the passenger) seat.
Midnight in a Perfect World on Amazon or order anywhere. The first book in a quartet chronicling the rise of a man from angry criminal to philanthropist. Midnight... is a distopic noirish novel featuring 'Duchess', a modified 1990 Subaru Legacy wagon.
I agree with most of what you say, and the chain would work if enclosed for trash protection, but I've helped build a couple of 'zuki 4x4's,a dn the transfer case drop and offset is only about 6" drop and 12" side off center, IIRC. the 6" drop would be about right to tuck the shaft under the headwithout raising the engine (may need a couple of inches max).
I'm not the one building it, I'm just giving my opinion as a fabricator based off of other projects I've been involved with.
I would be a cool project to be involve with though...
I'm not the one building it, I'm just giving my opinion as a fabricator based off of other projects I've been involved with.
I would be a cool project to be involve with though...
'90 Bermuda Blue L Wagon (Wife's),
Auto, AWD, Now with 275K + miles!
2005 Outback, 2.5 AWD (wife's new daily)
Auto, AWD, Now with 275K + miles!
2005 Outback, 2.5 AWD (wife's new daily)
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evolutionmovement
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I'm not saying your wrong, just arguing an alternative. If the shaft came down just right and not much lower than the oil pan, it would be fine, but I just wouldn't think things would work out that well.
I wonder then, would there be an entire small 4wd truck drivetrain that would work?
I wonder then, would there be an entire small 4wd truck drivetrain that would work?
Midnight in a Perfect World on Amazon or order anywhere. The first book in a quartet chronicling the rise of a man from angry criminal to philanthropist. Midnight... is a distopic noirish novel featuring 'Duchess', a modified 1990 Subaru Legacy wagon.
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All_talk
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BTW the "chain" I was talking about is the type use in many typical 4X4 transfer cases.
Drive shaft would likely be best on the drivers side due to the oil filter location, but a remote filter could be used. it would go under the motor mount so the shaft would pass through the (custom) sub frame and would end up about flush with the bottom of the pan. I certainly havent worked out all the details, but the basics look doable.
My application would be a 2-seat, mid-engined, AWD custom chassis wrapped in my '57 VW Beetle Body, here are a few drawings and such...
Gary
Drive shaft would likely be best on the drivers side due to the oil filter location, but a remote filter could be used. it would go under the motor mount so the shaft would pass through the (custom) sub frame and would end up about flush with the bottom of the pan. I certainly havent worked out all the details, but the basics look doable.
My application would be a 2-seat, mid-engined, AWD custom chassis wrapped in my '57 VW Beetle Body, here are a few drawings and such...
Gary
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Arctic Assassian
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I was actually thinking of putting this set up into my 70 beetle. I already have the suby engine in the car with an adapter plate. My father in law has another pan that I was going to start working on for the awd, then just move my body over. Thanks for the good info, i just hi jacked a wifi signal at my grandparents house, but my wife is tired from the trip and wanting to go to bed, so i'll chat about this later, thanks again.
Casey
Casey