Ok, who is? My question is, can the "ring and pinion" gears be removed or bypasses in order to make the transaxle into basically a transmission with 2 output shafts? I do not want a final drive ratio, I just want the transmission gears to turn the cv shaft outputs as a direct drive. Idea is to mount a FWD drivetrain longitudinal rather than laterally in a vehicle and have 2 output shafts for a set of cv shafts or drive shafts to be installed to make it an AWD setup. Follow me?
EDIT:
Here's a pic to show what I have in mind...
You can do this with a GM automatic, and possibly the Ford AXOD. GM automatics have planetary final drives, so you weld here and grind there and make it a 1:1 ratio instead of a 2.45:1 ratio.
With a manual transmission, no you can't do it.
You aren't the first person to think of this 
It's been brewing in my head for a while. The only problem is finding a differential short enough to plug in to the transmission. The Mazda 7" is the shortest I've found so far.
The next problem is that the GM automatics apparently will break easily at only 300-400hp. I want at least 600 if I am making an AWD car. Less than 600hp with AWD is kinda pointless.
Another question that you maybe should be asking is, what longitudinal final drives exist that are close to a 1:1 ratio?
I am fairly certain that the Honda CRV rear diff is around 1:1. It's also about the size of something you'd find in an R/C car.
I think, but am not sure, that the Haldex that VW used in transverse AWDs is as well. The neat thing about using a Haldex is that you weld the diff in the transmission and then you can have AWD, FWD, or RWD with the flip of a switch or two.
Would welding the differential provide a different result than what you are going for? I don't know so anyone should answer this,
While I'm post-spamming. I've always looked at the side gears in a Chrysler transmission with a bit of wonderment, in the sense of making a set of gears for it that reduce the final drive significantly for just this sort of AWD shenanigization.
Welding the diff and leaving the final drive in place in the transaxle would yield a double reduction once it went into the rear axle. Great for rock crawling, not great for going over 50MPH.
Knurled wrote:
Another question that you maybe should be asking is, what longitudinal final drives exist that are close to a 1:1 ratio?
I think the whole point of the OP's post was to remove the trans final drive so that using a F/R axle with a normal final drive would be acceptable.
FWIW, this concept (sideways FWD setup, with 2 final drives) has been put to use in rock-crawlers a lot. Pretty cool.
ProDarwin wrote:
Knurled wrote:
Another question that you maybe should be asking is, what longitudinal final drives exist that are close to a 1:1 ratio?
I think the whole point of the OP's post was to remove the trans final drive so that using a F/R axle with a normal final drive would be acceptable.
FWIW, this concept (sideways FWD setup, with 2 final drives) has been put to use in rock-crawlers a lot. Pretty cool.
Yes. That's it. I cannot find anything with a 1:1 differential drive, let alone something to handle 650+ ft lbs.
The only realistic way to do this is to stuff the guts of a trans into a homemade case, or build gearboxes to go on each output to speed them back up. With a custom spool you might clear a 1:1 final drive in a stock case, but then you lost the center diff.
I have done exactly this with a reverse rotation honda engine and auto trans. It was a single seat mid engine tube frame rock buggy with front Toyota axles.
I was about to say that I just sold it a few years ago...it was 15 years ago! Good lord
Kenny_McCormic wrote:
The only realistic way to do this is to stuff the guts of a trans into a homemade case, or build gearboxes to go on each output to speed them back up. With a custom spool you might clear a 1:1 final drive in a stock case, but then you lost the center diff.
The only problem with the gearboxes is the losses involved. You're reducing, then reducing again with the final drive in the trans, then speeding it up again with the box, then reducing again with the final drive at the axle.
If you're going to go to that much trouble, you'd be better off to get a longitudinal AWD transmission (Audi, it's the only way to fly) and make a transfer box for the "rear" output to get sent forward to the front wheels. Audi driveshafts are all reverse rotation, something to consider. They didn't have a transfer gear set like Subarus do, the center diff is driven directly off of the countershaft.
This is what I want to do.
Yep, appears your best option is to hack the final drive of a 4T65.
The TH125 is strong and can be built stronger, but on O/D.
Go check on Pirate4x4.com board. There are several competition single seat rock crawlers that use this exact set up. Lets them run smaller and more compact set ups with super low gears in the axles.
As someone who has opened a 4T60E, they have a tiny diffwith spider gears as well. The weak point on these is something called thr reverse reaction drum. Its a relatively thin steel drum that connects two sets of clutch packs thatlikes to shear at both sides if you apply too much torque with lots of traction or large shocks to the drivetrainlike youd get with a shift kit.
GM's Ecotec power manual tells you how to not only attach an Ecotec to a 4T65 (they never coexisted in nature) but how to beef up the trans to handle 1200hp for at least a few seconds at a time.
Plus they used to sell axle ends to bolt 930-style CVs to them. Not sure if they still do.
In reply to Knurled:
Sad part about that trans build is you lose 4th gear and the lock-up converter.
NO. AUTOMATICS.
That is all. Manual transmission options onry. Well, maybe an automatic if it can be calibrated to manually shift via switches/paddles.
former520 wrote:
Go check on Pirate4x4.com board. There are several competition single seat rock crawlers that use this exact set up. Lets them run smaller and more compact set ups with super low gears in the axles.
I've seen them before, but the gear reduction is waaaay too much to make a useable road race car.
The overall problem is the final rive ratio. You are basically going to have something that wont go over 50 mph.
Think of it like a rear wheel drive car. Power goes through the trans and then the rearend. This is what you have with the axles sticking out of the FWD layout. Then, you need to go through ANOTHER rear end. You are going to reduce your wheel speed twice.
Rob R.
wvumtnbkr wrote:
The overall problem is the final rive ratio. You are basically going to have something that wont go over 50 mph.
Think of it like a rear wheel drive car. Power goes through the trans and then the rearend. This is what you have with the axles sticking out of the FWD layout. Then, you need to go through ANOTHER rear end. You are going to reduce your wheel speed twice.
Rob R.
Exactly. I'm trying to figure out if it's possible to remove this from the FWD transaxle because I can't find a rear end that's a 1:1 axle ratio.
My thought?
Leave the transaxle alone as most leverage a small pinion gear that drives the larger ring gear and they are usually spirial cut, etc. The pinion gear is also many times a permanent part of one of the two main shafts in the transaxles.
So I'd find a pair of differentials that are the appropriate gear ratio, weld them up and drive the m backwards to step the output up to where it needs to be for your final drives. IT sucks, but that is the only way around it without something entirely custom.
Speaking of custom, another thought would be to machine the pinion gear off or down to accept a chain drive from a transfer case and then machine the differential to accept another chain drive gear, likely on the backside of the ring gear. That might get you closer to what you need.
If I could find a transaxle with something in the very low 3's or high 2's and then get front and rear axles in the high 1's or low 2's, then we'd be in business. But I can't find that stuff, as far as the differential gears go. Maybe I need to start looking at the Boneville speedster catalogs?
