Right Angle Drive; Serious Power and RPM , GRM Challenge budget

I think most Know I want to make This C4 a Mid Engine Car.  I've Dwelt on the Drive train for more than A Minute or Two and More like A year or Two. 

I have Two engines I Can use A Chevy 350 and an 'Ol boat motor Mercrusier 454, Gonna Go BB but stuff Happens,

Three Trans to choose From for this build,  a 4t65hd, a 4t80 ,or A TH425, The 425 will handle all I can throw at it no questions. using the 350 would likely allow using the Transverse tranny's and really make it a Drop in ( cradle swap) and I think the .'65' is strong Enough and Lighter than the '80', The 350 also Came in the car so no Budget hit, but selling it will generate more than I have in the BB,

so BB and 425, I've studied Mounting the engine and trans faceing Forward, and  Backwards and Now sideways, each way has it's Logistical Problems Because It will be In Front of the Diff. not on Top

Facing rearward engine is Biased to the pass side to keep the Trans Output Straight to the Diff. but it's reversed in rotation so offset it and make a gear to reverse Direction, then couple to the Diff.

Facing forward with eng. Trans. splitting the differential between them, a gear drive Like a Quick change Has to send the Power back to the Diff. Like a Jack shaft running between engine and trans through the Chain cover on to the Diff.  I like this Best but it's Longer  Into the Driver Cockpit with Either longitudial Placement.

Sideways , really most Simple, Mount it, put a drive Shaft from the 425 output shaft to the diff. and go. except you Have two differentials, 1 on the 425 ,, 1 on the Car between the 2 gear reduction is around 5.87 to1,

 where do I find a Right angle Drive to replace the 425 diff. 500 ft.. lbs. torque 7000 rpm Capable,  boston Gear sells Gears that can be Fabbed into a Case But Again I want it at The Challenge 2020 

Never violate the K.I.S.S rule. 

I think if you use a diff and pin one output shaft so it cannot rotate, then the other output shaft will go double speed (I think).

So something like a 2.93 would actually be more like a 1.5:1. Might be "tall" enough to work. The spider gears probably won't like it, however.

In reply to Stampie :

Which One?

In reply to Robbie :

If It went Dbl. speed it alone would be high 5's but it isn't possible because the ring and pinion are what they are and the pinion is connected to the Engine speed, 

In reply to GTXVette :

I'm pretty sure driveshaft speed is higher than axle speed. So if you double the axle speed while keeping the driveshaft speed constant, then the ratio is cut in half ...

Right?

I say 4t65 or 80, weld its internal diff, use its passenger side output to the vette diff and just put a fluid plug in the drivers side axle hole. Yes it will be a very steep reduction but it will also have 4 gears. The 80 is likely to have a taller diff ratio than the 65. The C4 was available with very tall rear gears which you may either already have or be able to trade your whole diff assembly for at no cost. If you assume a 3.11:1 4t80 and a 2.59:1 C4 diff, you would top out 4th gear at 100mph if you spin the engine to 7000. 100mph could be good enough to do high 12s, or potentially quicker if you want to ride the rev limiter the last couple hundred feet of the 1/4. 

 If you don't want to spin that high (or you want to go faster!!) you could also try to defeat the final drive reduction in the 4t80 and have a 'normal' output from it.  If you look at this diagram of the 4t80 it looks to me like if you just completely leave out the sun gear for the planetary set attached to the differential and then pin/bolt/weld the final drive sun gear shaft to the output shaft and weld up the actual diff (spider gears), you'd end up with a 1:1 diff ratio. You'd probably have to cut off the axle end of that  driver side output shaft so that you could insert it from the passenger side of the trans with the other piece it'd be welded/attached to, but that wouldn't matter since you wouldn't be using that end to drive a cv axle anyway and that shaft itself doesn't support or locate anything else that i can tell. 

I've rebuilt 4t80s before so it seems doable to me since i've already been in them and more or less understand how the planetary differential gear reduction part works. If you've never worked inside an automatic before this might sound like some really ambitious mumbo jumbo. 

Can you find a boat with a chevy engine and a v drive in the woods somewhere?

   VIGO , I Have been Past the Valve body on most GM Trannys except for T's and only done silenoids on the 80's.

I understand how the Planetary drive can be Manipulated, are you suggesting to mount the T in an L configuration,  A 'T' tranny may be the easy button and Folks Have put BBChevy engines in Fiero's with a T 60 trans but don't know what would Break First, so the 65hd is what comes in supercharged cars and is stronger and my first choice i think the 80 is heavier and with an all Iron BB it's gettin heavy

. If you get to N georgia I will send you one back to Xperiment on, But San Antonio is Way south, I'd Get to Dallas and still have that much Farther to Go.

tell me more about how to mess with the Planetary's to Achive this 1.1.

anyone one else , I am interested in Robbie's Theroy also as that would be my preferred trans. the jack shaft Idea my be easier

In reply to Patrick :

Scarey stuff in the woods round here! V drive gets the Reverse rotation pretty Easy, Thanks

Did You Need a boat Motor? Lol

 saw some as Low as 350ish on E Bay And I wouldn't need that angle snout so Maybe Find something Local. Atl.Area Is Said to be Largest Land Locked Boating Population But They Don't 'Race" around Here So those drives may or May Not Be available, Lots Of Ski boats and Small Lake Cruisers tho.

 Thanks Patrick .

                                    A Monster Lurks Within. 

 Am i crazy ?  I want To Say Momma had Me tested,  But in truth the tests were Inconclusive, So...........

   No more time than being Handed A simple Solution For a big problem Than I want to complecate it more.

     How's about take out the torque Converter and Put in a Clutch to drive the chain and then Mount the v-drive case mounted to the Super T-10 I have And driving the Stock Diff.

          inquireing Minds want to know

I understand how the Planetary drive can be Manipulated, are you suggesting to mount the T in an L configuration

I was suggesting mounting the engine longitudinally, with the front (belts end) facing the corvette diff, and engine offset slightly to passenger side so the 4t80 passenger axle output will line up with the C4 diff.  If you use a CV axle to connect the 4t80 to vette diff you could even offset it towards center a little more. I  don't really know how feasible it is from a space point of view.  

In reply to Vigo :

In a c4 you can basically rest your elbow on the rear diff yoke while driving if the tunnel sheetmetal wasn’t in the way.  I’m envisioning your example as engine instead of passenger seat, which may actually work.  

Having the belt side Face the rear, makes the Rotation CC,

starting to see it Engine Backwards w/425 / V-Driive Reverser straight into Vette Diff, no th425 diff.

there has been talk of rebuild the 425 with a long-er Main shaft( 400's had 3 Length's) and Accompaning Tail shaft Housing To Get A support Near the End ? but not really neeed if plate to hold Vdrive Gear housing is put there instead.

this does Allow Engine to be Biased to the Pass. side A Bit , It will only take Me and about 500Lbs to balance out.     Lol

GTXVette said:

Facing rearward engine is Biased to the pass side to keep the Trans Output Straight to the Diff. but it's reversed in rotation so offset it and make a gear to reverse Direction, then couple to the Diff.

Can you mount the diff upside down so the ring gear's on the other side?

My understanding (worth possibly less than you're paying for it) is that the ring and pinion is generally plenty strong in reverse, just noisy.

When Rotating a Diff. Upside Down you also have Lube Problems and a gear is cut with a Curve in them to allow for a Longer contact when teeth Mesh

,when turning Backwards you get the back side of that angle and stregnth diminishes also. It Might last a Minute or two  not worth trying and the 425 diff has an angle that would raise the axle centerline,

the Idea is to move it past the engine so it's not on top of it. and in the ongoing Delusion If the reverser is at the Chains Tranny end ANY Trans could be used,    with that in mind I would do a Powerglide

In a c4 you can basically rest your elbow on the rear diff yoke while driving if the tunnel sheetmetal wasn’t in the way.  I’m envisioning your example as engine instead of passenger seat, which may actually work.  

Well... that would be some interesting packaging.