AWD Omni?

[zin]

OK so AWD and big HP in an Omni, sounds pretty cool eh? I've had a thing about making this happen for some time now. Just can't stand having the HP to wax most cars, but getting walked off the line by some RWD or AWD car. So, now I'm going to try and do something about it, and no not just installing a LSD (though that might happen too).

I just picked up the PTO (for lack of a better term) and the rear diff from a 91 AWD Caravan. Spent all day at Pick A Part trying to get these pieces off the damn van, but in doing so it appears that the conversion might not be as difficult as I had imagined. Don't get me wrong, this project is still very much in it's infancy, but I wanted to solicit anyone that might have some knowledge of how the stock AWD system works to add anything they might think relevant. I'd really like to find a FSM that covers this system in the hopes it might shed some light. Thanks to all and anyone that can help this little project along.

Mike

[Vigo]

i dont know much about it, but i know that the 'pto' per se of the caravan awd system splines into the actual diff carrier of the 604, so you will need that diff out of the donor to make anything work, and of course you'll be using at least the inboard end of the passenger cv shaft from the van, probly have to have it custom built when you get measurements.

you're probably going to have to figure out how to completely relocate the steering rack to get the driveshaft to go through there, and the only place to go is down really.. i dont own an l body so i might be wrong on that..

i cant remember if the gas tank is in the way on an L, you may have to get a fuel cell or cut a big chunk off the gas tank. custom driveshaft. i dont know if the lbody rear axle is going to be in the way of the rear driveshaft, but if so you will have to cut out the whole middle section and make a big hoop under or over the driveshaft. you'll probly have to enlarge the tunnel for the whole length of the driveshaft and bolt up the viscous coupling in there somewhere.

the rear diff mounts to the body iirc and halfshafts go to the hubs mounted on the solid axle.. me thinks the easiest way to get powered hubs on an l-body axle is to cut them off the caravan axle and weld them on the omni one : / or convert to a narrowed minivan rear axle with leafs and narrowed shafts too and the whole bit.

now even if you get all the physical mounting issues fixed up, you're going to have to make sure the front and rear diff ratios are the exact same to avoid binding/burning up the viscous coupling.. in all likelihood this means wildly staggered tire sizes from front to rear, or a custom ring & pinion for the rear diff.

it goes on and on.

you picked a tough one, let us know how it goes

[tvanlant]

Sorry, I don't have any knowledge to shed, but good luck with the project.

Have you considered a RWD conversion, instead? Wouldn't that be quite a bit easier than AWD?

Also, what do you plan on doing to the drivetrain to make it handle the abuse/power?

[Vigo]

hehe i thought my response pretty much equated to 'case closed'..

[rbryant]

hehe i thought my response pretty much equated to 'case closed'..

Yea honestly I didn't even read it... This has been so covered that it should be read about not posted about.

That said you did cover most of the issues! I am in a crappy mood so I turned into the search button nazi.

-Rich

[johnl]

Ah, come on Rich. Lighten up on Mike. I just searched "AWD Omni" "AWD Mini" "AWD Conversion" and came up with zilch for three or four pages. And, Vigo, you are sooo negative. I want an AWD omni too! Someone's gotta do it and figure it out. I mean, the hybrid conversion idea once had a similar list of problems and now its no so intimidating, not such a big deal.

[Clay]

the only thing that I think will be an issue is the mini van setup is pretty power limited. Your not going to be able to dump any real power through that AWD setup before you start leaving piece and parts on the ground.

[rbryant]

AWD probably doesn't work because it is only a 3 character search...

Perhaps it can be added to the special 3 letter search engine. I am sure it can't be that hard to find the thread though....

-Rich

[rbryant]

http://www.turbo-mopar.com/forums/sh...light=traction
http://www.turbododge.com/forums/f11...y-not-awd.html

It is also covered in the old SDML forums but I am not sure if search is working there anymore.

-Rich

[WVRampage]

With all the parts and time,Id try and see what needed done to mount the pto and get the drive shaft to the rear.I wouldnt worry at all about the rear untill the trans and pto were mounted.I dont want to discurage you but its not gona be easy but if you have the parts and a car to have down for a while Id try it.You will also need the diff and the right side bearing mount from the trans.

[Vigo]

i want an AWD k-car or l-body too, but imo youd probly be better off adapting parts from a completely unrelated platform, up to and including adapting a completely different rear axle. i dont think the caravan parts have any particular advantage to any platform except another van.

that said.. i have no constructive input on which parts to go looking for. : /

[WVRampage]

After the PTO any rear could be used,the pto can handle a 3.8 in a heavy van on ice and not explode,that being said a 2.2 or 2.5 would have more power but would be in a much lighter car.Im sure a toyota or nissan rear end would be small enough and light enough as well,you would just need to have the right gears so a toyota has more after market.If I had the trans parts and the PTO I would try it with a charger I have for parts.

[turbovanman²]

The minivans K-member is reshaped at the rear to allow the driveshaft to pass thru, its not straight anymore but a curved section. I can't remember what they do with the rack. I guess you could cut and section the van K-member, then you can upgrade to cast control arms,

The driveshaft goes next to the gas tank on the van, not thru it thank god. The rear axle still is mounted on leaf springs but the bolt pattern is the large one.

Good luck, it should be interesting to see how this will work out.

BTW, I think this system could take alot of power, it looks pretty beefy and if a turboed Civic can use a stock AWD Civic setup with breaking it, I am sure the van stuff can take a beating,

[Vigo]

somebody needs to figure out if you can swap the 604 awd diff carrier into the 3spd or not.. cuz thats the only way to make the pto work without $$$$$$.

im pretty sure they're dimensionally really close so if the 3spd ring gear will bolt on and its not offset from stock much it should be possible to make it work.

[zin]

the only thing that I think will be an issue is the mini van setup is pretty power limited. Your not going to be able to dump any real power through that AWD setup before you start leaving piece and parts on the ground.

Not too worried about that, I'll be starting with low boost, plus the Omni is WAY lighter, that'll buy a lot of room to work. Course, if it doesn't break, I must not be making enough power!

The minivans K-member is reshaped at the rear to allow the driveshaft to pass thru, its not straight anymore but a curved section. I can't remember what they do with the rack.

I thought about pulling the K member when I was pulling the parts, as I had to take the K member out to get the parts, but this is CA and that means bend over when you get the parts to the cashier, as it was they overcharged me, I'll be writing a letter to corporate about that...

The rack is raised by a funky bracket/crossmember and forms kind of a driveshaft hoop that the PTO's driveshaft runs through, got that too, just in case.

somebody needs to figure out if you can swap the 604 awd diff carrier into the 3spd or not.. cuz thats the only way to make the pto work without $$$$$$.

The PTO bolts on in place of the pass side extension housing, I've got the PTO, adapter plate and the brace that helps connect it to the trans, it also bolts onto the block in place of the intermediate shaft mount. The pass side driveshaft was really long, not sure if it was engaging the diff on the trans or splines on the ID of the PTO's input shaft. I'm really hoping its the later and not the former, which would make sense from a production stand point, just bolt on the PTO, no special internal parts required to convert a FWD trans to AWD, other than the adapter plate. If the extension housings are not compatible (or adaptable) I might just have to put a 604 in it. This is something I've also been keen on, but I want to go in stages. A 4speed auto conversion is a project in itself!

I should probably go back and pick up the pass side drive shaft and the rear driven hubs, but those shysters at Pick Your Part really pissed me off! I could start another thread or go off on a rant for three days about it, but I'll control myself... for now. Just really hate to give them any more of my $$ I should try calling a "real" JY at least that way I don't have to come home looking like I've been in the coal mine for days!

This will, no doubt, be a project that will be in the works for some time, I'll update as progress is made, or obstacles are encountered. I do have to finish remodeling the garage (to have a good place to work) and landscape the backyard(in order appease the wife) before I can really get going, but for now, I'm optimistic.

Here's a couple of crappy phone camera picts of the parts as drug up to the cashier. Sure that's a drive shaft attached to the diff, so what if it mounts to it and doesn't turn.... Idiots!!! Left to right, the whole lot of it, next, a closer shot of the PTO, then the rack spacer/bracket, and a shot of one of the rear hubs.

As always I appreciate the input, feel free to point out things you think might be a problem, even if you don't have a solution, I might not have thought of it and it might just save my sanity! Of course the fact that I'm even contemplating this project brings that into question!

[Ondonti]

more pictures would be cool

There is also a guy here with a PT cruiser who said a controller for the a604 trans would not be that hard for his trans guy. Since there are people who can rebuild those transmissions to take a huge beating and it has much beefier parts then the 3-spd you might be able to pull that off.

[BLUEBALL]

AWD,what an idea!! Get ready to find place for starter and turbo while your out fabbing. Just a couple pieces need modified.

[Vigo]

hmm we need more / clearer pics of that pto!!

it looks like it bolts on right where the carrier bearing for the intermediate shaft would, and has its own stub shaft which goes into the stock tranny's diff..

if so. HELL YES. of course i think omnis usually had the smaller splines on the diff so you might end up swapping to a different diff carrier while you have it all apart to make that stub shaft go in there

if the above observations are correct than it looks like the pto would be more underneath the power steering area than the turbo/starter, so its possible you might not have interference there..

i dunno why but the pics made me more interested, post some more!

[BLUEBALL]

Well it was about 10 years ago i had the stuff to lay out. The transfer case will bolt up to trans. It will be in the starter and turbo area. So time to get your fab on. Have fun with it.

Be easier and less parasitic drag to go RWD. Unless you got ungodly power,you can still go fast without it.

[Turbodave]

After reading this thread I was thinking that if you were building a car from the ground up to use this setup why not start with a 2.4 Turbo engine and run the A604 based 4 speed auto behind it. The starter is in the front on the 2.4 and the turbo would be mounted higher with a better chance of clearing the diff.

Is that caravan diff a 1:1 ratio? If the PTO is driven off the diff of the trans I would guess that it has to be. That may eliminate the worry about getting the proper front/rear gear ratios.

I've got a sick mental picture of my 90 voyager with a 2.4 turbo awd setup in it now...