AWD Rear Axle/Suspension Questions - Hybrid Conversion

[TaxiVan]

Okay folks, stay with me, this one's tricky. I am close to being in a position to get my van back on the road again. Although I had other ideas, it occurred to me that this van is my bread and butter, and every day it sits is costing me money by not being able to carry those extra two passengers. Therefore, the time involved in the diesel swap I intended is just not going to be worth it in this case.

I have read about another user here who has successfully swapped an electronic part-time 4x4 setup from an S-10 into their AWD. This is an idea I had considered simply to upgrade my AWD, but it has given me another idea for a hybrid conversion. I won't divulge full details until I know it will work as planned, but I need advice/ideas in fairly general areas of required modifications for my idea. Does anyone know who did the 4WD conversion? I would like to get in touch with them to see how easy/difficult it is.

A major part of the conversion requires swapping my rear differential for a trans-axle set-up. This is where it gets tricky. I am not sure whether my rear suspension is coil or leaf, but I presume coil. Just to keep it all GM and possibly make for an easier conversion, I am considering an older TH-125 or TH440-T4 set-up, highly prevalent in early 80s-early 90s GM FWD. I am thinking a TH440-T4 from a late-80s/early-90s H-body (Delta 88/Bonneville/LeSabre/Park Avenue), or something of the like, would be perfect. I believe these use a larger lug pattern like our vans. These are some of the questions on my mind....

1) Theoretically speaking, is it possible to put a transverse GM transaxle in the rear of an AWD Astro/Safari?

2) Can such a transaxle be damaged by being free-wheeled (towed, as it were) at low speeds when not being used?

3) If not the FWD H-body, which GM FWD cars use the same lug pattern as our vans? W-body (88-94 Lumina/Cutlass/GP/Regal)?

And yes, this scientist is definitely mad, but there is a method to my madness... If my idea works as I think it will... a 40-mpg Astro/Safari will be born.

[DRZ]

Dreaming is fun but to start, your Astro has leaf rear springs and would be hard to change unless the fuel tank goes somewhere else imo.

[TaxiVan]

Dreaming is fun but to start, your Astro has leaf rear springs and would be hard to change unless the fuel tank goes somewhere else imo.

Actually, that might be perfect... I wonder if brackets could be made to support the transaxle by piggy-backing the leaf spring mounts?

[Jasen]

I don't think you can use a FWD transaxle. Been some time sense I worked on a Toronado but as I recall it has a big bell housing just like a regular tranny, maybe bigger and the thing in itself is pretty huge, seeing you've got a whole tranny configured sideway's. Don't think you have the vertical clearance for it back there in regards to suspension travel. GM did do RWD transaxles, 61-63 in Pont. Tempest's and Old's Cutlass F 85 and of course the Corvair. The Pont. and Old's ran a torque tube drive shaft, which would be to short for the van if you could find the set up for a reasonable price. The problem with the Corvair is it was basically a reversed tranny seeing the motor was behind it.
Then you have to figure in building some hard points closer to the center line to mount a trans axle to as well as the rear suspension.

[TaxiVan]

I don't think you can use a FWD transaxle. Been some time sense I worked on a Toronado but as I recall it has a big bell housing just like a regular tranny, maybe bigger and the thing in itself is pretty huge, seeing you've got a whole tranny configured sideway's. Don't think you have the vertical clearance for it back there in regards to suspension travel. GM did do RWD transaxles, 61-63 in Pont. Tempest's and Old's Cutlass F 85 and of course the Corvair. The Pont. and Old's ran a torque tube drive shaft, which would be to short for the van if you could find the set up for a reasonable price. The problem with the Corvair is it was basically a reversed tranny seeing the motor was behind it.
Then you have to figure in building some hard points closer to the center line to mount a trans axle to as well as the rear suspension.

All good points. The transverse unit used for 60-degree V6s might be a bit smaller. I originally considered a Toronado/Eldo unit, but figured a newer transverse unit would likely fit better, for the reasons you have stated. Another problem with the Corvair unit is that I believe most of them were manuals. That said, my idea requires a separate drivetrain in the rear, do you have any other ideas?

[Jasen]

Don't know why it didn't come to mind before, Corvette and Jaguar.

[TaxiVan]

Don't know why it didn't come to mind before, Corvette and Jaguar.

Nice, Jasen... I'd forgotten about the C5 'Vette as well. Looking at this photo, it certainly seems this setup would swap quite well for such a conversion.... Bolting the center section into the floor should be easy... Just have to adapt the suspension... My idea involves two separate drive-trains and it would be nice to have full-range capability on either system. Does anyone know if this setup uses a similar style controller to the 4L60E/4L80E?

[Shad0wXCalibur]

That reminds me of a Dodge Intrepid transmission. I walked past one in the junkyard once. The whole drivetrain is longitudinal like a truck except I thought they were FWD. Well it is. The CV axles came out the sides of the transmission like that picture. Had never seen that before. Of course a transmission in the REAR like on the corvette is like woah to me. Didn't know they were made like that. Kinda trippy looking.

[Mr_Roboto]

The C5 axle is a 4L60E, or a T56. Later stuff has a 6L80E or 6l80E I think. Don't quote me on the 6 spd autos however.

[Jasen]

That reminds me of a Dodge Intrepid transmission. I walked past one in the junkyard once. The whole drivetrain is longitudinal like a truck except I thought they were FWD. Well it is. The CV axles came out the sides of the transmission like that picture. Had never seen that before. Of course a transmission in the REAR like on the corvette is like woah to me. Didn't know they were made like that. Kinda trippy looking.

I had a 95 Intrepid, bought it new. When I test drove it I said to the salesman, I thought these were FWD. They don't drive like any FWD I'd ever driven before. It was a nice car, but they had wimpy front rotors and they would go out of true every few months even with me spending 75% of my driving on the Freeway. After 3 rotor turns and a new set of rotors I sold it at 20 months, about 5-6 months after that they had a recall on the rotors.

[TaxiVan]

The C5 axle is a 4L60E, or a T56. Later stuff has a 6L80E or 6l80E I think. Don't quote me on the 6 spd autos however.

So basically a 4L60E with a differential in the tailshaft housing? Good to know...

[tedanderson]

GM did do RWD transaxles, 61-63 in Pont. Tempest's and Old's Cutlass F 85 and of course the Corvair.

Don't forget the Fiero. Well.. OK. So technically it was MID engine but for all purposes of discussion here, it was indeed a rear transaxle setup.

[Jasen]

Oh yea, the Firero. Talk about the best place to put a distributor

[Lumpy]

Oh yea, the Firero...

I could look out the inside rear view mirror in mine and see flames coming out of the engine vent, roughly eight inches from my head.


Lump

[TaxiVan]

GM did do RWD transaxles, 61-63 in Pont. Tempest's and Old's Cutlass F 85 and of course the Corvair.

Don't forget the Fiero. Well.. OK. So technically it was MID engine but for all purposes of discussion here, it was indeed a rear transaxle setup.

Technically, it was really an X/A-body setup moved to the rear...

Oh yea, the Firero. Talk about the best place to put a distributor

Actually, from my understanding, the entire problem with the Fiero was the 2.5L rod-thrower offered as the base power plant. An enthusiast I used to know told me that there was a 100% failure rate on the 2.5L due to 1 in 4 connecting rods being weak. They further explained that the lack of adequate ventilation in the rear of the Fiero facilitated engine fires from the oil that coated the exhaust manifolds when these failures occurred. I myself have had one of these in an A-body that threw a rod through the block and kept running, slinging oil all over the place, and I've seen plenty of V-6 Fieros still out there without problems, so I kinda think they are right.

I would venture a guess that a 61-63 Tempest, Corvair or Cutlass F-85 is gonna be a little hard to find at a bone-yard. A '97-up Vette might not.

[cowboydan]

taxivan, it is possible to swap in part time 4x4 from awd, rather simple. t-case, front drive shaft, front diff axle tube (long side), wiring for the selector on the dash. as far as some pics of the corvette rear end, you have 2 issues, torque tube and housing the transmission in the rear. converting a van would be right up there with the best of ideas. there will be alot of gemoetry and physics to think about

[TaxiVan]

taxivan, it is possible to swap in part time 4x4 from awd, rather simple. t-case, front drive shaft, front diff axle tube (long side), wiring for the selector on the dash. as far as some pics of the corvette rear end, you have 2 issues, torque tube and housing the transmission in the rear. converting a van would be right up there with the best of ideas. there will be alot of gemoetry and physics to think about

Actually, my hybrid power source is intended to be directly coupled to the rear transaxle. According to another user, this setup actually is at least largely based on a 4L60E, so I imagine it would be possible to bolt a flexplate to its torque converter and couple the hybrid power source to that. I think it can all be done, it's just a matter of adapting the suspension to the van, and, as you stated, there is geometry to be considered there.

[cowboydan]

it's a solid idea if you can manage the complexity of the fab work.

[TaxiVan]

Food for thought... does anyone else think that 'vette transaxle's "differential" section looks like it might actually be a front diff from an Astro/Safari or Tahoe/Suburban, just turned around?

[MadMaxiVan]

im curious....besides the complexity...of dual engines/drivetrains/cooling systems etc.

wheres your passengers gonna sit?

back in the daze,i dimly recall two cars,both station wagons,one had two 455-s in it,front and rear.
the other had like a smallblock chevy? and a jet turbine mounted in the back..
both were street racers that literally smoked the competition..
someone out in Cali might actually recall these cars..?