Swede51

Hello; I am a 59y.o. newbee to computers and forums. I hope I will be asking an appropriate question... I am partially disabled (legs) and for my last project I chose a 1969 Fiberfab Avenger (GT-40 lookalike) kit car on a VW pan. I also bought an old MidEngineering frame for those kit cars with a midengine 350 Chevy mated to a rebuilt Olds TH-425 Switch Pitch transaxle. The chassis ran great. But when we tried to put the body on the frame, the distributor and carb hit the fiberglass and rear windshield. A friend said I should see if an LS-1 engine would mate to the Toro transaxle as the LS-1 has no distributor and the intake runners are only inches above the valve covers. So, would anyone know if an LS-1 can be mated to an Olds TH-425 transaxle? Again, I hope my 1st forum post is an appropriate question... Thank you; Swede

nunan0219

iTrader: (2)

i'm not sure how its bolted or anything, but if its a bolt pattern similar to the BOP transmissions (th350 and 400) than all you need is the adapter plate to convert to the chevy bolt pattern. also, i'm not sure if the transaxle u speak of is manual or automatic (like the toronados, IIRC), but you need to see if they share a bolt pattern similiar to the new automatics like the 350s and 400s. for that you can buy an adapter flexplate/flywheel

SuicdRn

Swede....The LS will mate to the TH 425 but, as mentioned you will need the adapters. I have been doing a lot of research on this and it appears that you will also have some block clearancing issues at the differential. Minor as I understand it but doable.I'm not sure where your head is in this conversion but you have alternatives in the engine choice that will not only be cheaper but a lot easier.The original 425 or 455 " motors that came on your trans had a very low manifold for hood clearance. Any big block Olds with this manifold should work for you.It is by no means a performance manifold.As with the rest of the Olds big blocks ....it weighs a ton!!I have been running the Toro setup for over 20 years in a full bodied VW and it is extremely heavy in the rear.In your kit car your weight bias would be way out of line.Edelbrock aluminum heads would help you but with that factory intake you would defeat most of the horsepower gains.I recently have been considering the LS motor for my setup,that's what has drawn me here.I don't have the space limitations that you currently have.Plus, I'm considering downsizing to the TH325-4L trans.It's a lighter duty trans that comes with an overdrive and it also weighs 75 pounds less than the TH425.Let me know if I can be of any further assistance. Norm.....just another ole fart :-).......PS..I do have an original Toro intake if you decide that way.

Nashty

iTrader: (7)

Man that thing is cool, what a pretty color combination. What kind of VW is that? Are those 37 Ford headlights?

As for the original question. How about an late model GM FWD 5.3 setup and ditch the Olds transaxle entirely?

Swede51

Thanks to all who replied to my LS-1 to Toronado TH-425 transaxle question. Lots to look into and digest. It may be more difficult to do than I thought. But again, thanks to all who responded! Sincerely; Len Swenson

SuicdRn

No problem Swede.Nashty, my car started out as a VW Type III Fastback.It's been chopped 3 inches and cut into a pickup.Also has suicide doors and yes, 37 Ford headlights.

ls1countach

Yes, the LS1 will bolt to a TH425. I have done this in my Fiero Base Countach kitcar. It took 2 years to do it and it is all custom. Bell housing adapter plate is used but modifications are needed to make it work. Get the grinder out to cut away the trans casing for the flexplate teeth to clear. Mill or machine off the bottom of the entire block and front/rear covers down 1/4" to raise the oil pan after you ground out and notched the final drive to just make it bolt up. Also you have to mill the side of the block down to make it bolt up and some gasket mods are needed as well. Then get a Morosso steel deep sump oil pan and hack it up to make it work, but dont forget the oil pump pick up tube needs to be modified, rod cap bolts need to be modified, the oil filter has to be relocated by running tube lines between the engine and flexplate and locating a ford oil filter on the passenger firewall. You will also run into motor mount issues and adapter plates have to be made to raise the motormounts evenly because the right one will be hitting the final drive gearbox. The left axle has to go thru the oil pan and it is extensive work to do. The axle bearing support has to be modified as well. The starter is another issue and mods to the bendix, and shims are required. Also you get into exhaust issues. I had to flip the headers upside down pointed forward because the final drive gears are right there in the way. And dont forget the custom axles have to be made. The engine will have to be offset 1" to the passenger side to center the axles on the car. The issues I am facing now are the flexplate is not strong enough and I have to change it out because Rev and 2nd gear selections are making the torque converter balloon and makiking the flexplate flex and rub, "something". If I dont change it I can foresee the flexplate cracking around the crankshaft if it isnt cracked already. Believe me, It is a REAL BITCH, but I have done all this. I am SURE I am forgetting some other issues I ran into that dont come to mind right now.
Yes I have pictures if you are still interested in doing this or if you are near houston texas you can come take a look at what I have done.
Good Luck.

Burning Oil

Hello, this is my first post here and I joined just in hopes of contacting you. I really like what you did with your Fiero. I have been plaining on a kit car build for atleast to years and just got to the point where Im ready to get serious. I have been logging many hours on the internet seaching for ideas. I want a rear/mid engine car, but one of the major expences is finding a transaxle and I want an automatic.
I see you are in Houston, so am I. I would really like to pick your brain and even take a look at what you did.
I PM'ed you with my phone and email.

Burning Oil

A small thread jack, but still on the TH425.

I have a question/s. Is the input shaft on a TH425 th325...ect turned the the opposite way compaired to a normal engine/trans mounting? So does the output shaft spin the same direction in the forward gears as input shaft?
I ask this because I want to flip the engine so the front faces the rear of the car. This means the differential must be flipped. The stress on the pinion gear would then have a tendancy to push in on the ring gear. That takes the load more off the bearing races and puts stress on the pinion nut, right?
That does not seem like a good thing and please correct me if Im wrong.
Can someone confirm the crank shaft direction CW or CCW as you look at flywheel for me.

tonypaul

iTrader: (2)

The th425 runs backwards up to the final drive, the final drive is what rerotates for the proper direction in the normal direction for fwd cadi, eldorado,ect. To run the th425 in a reverse rotation is a tricky situation, if you can flip the final drive (which is no simple task) a complex adapter will need to be made. The real problem is that it raises your axle center line well up into the oilpan.

Lookup Pennocks fiero forum and do a search for "cardealer" (its me) I did a reverse rotation sbc fiero drag car a long time ago. I now have built a Diablo replica with sbc/archie kit but Im currently building a twin turbo LS1 with a th425 in a reverse rotation. Im not useing the stock th425 final drive, Im using a front diff of a chevy 4x4 truck. This will allow me to run it in a reverse rotation and get a real good mid-engine placement. Here are some old mockup pics to show what the general concept is- its progess quite a bit since this...

jasmot

Hello All

I have a problem with my th425,when I put drive and then put retro the car make a hit and again put drive and another hit.
The hit appear when I change from drive to retro and the same retro to drive.
I rebuild all the transmission and taxle,the hit its the same,can be the modulator or line? or valve body ??
Thanks,
Juan

ryeguy2006a

iTrader: (27)

So not sure if you have to use the Toronado transmission, but another alternative could be using the LS4 engine/trans that came in the V8 FWD Cars. Might make your LS swap easier and provide an overdrive.

G Atsma

Not sure that will work. The TH425 is a north-south tranny, where the one you mention lays crossways.