well i toyed with the idea of a standard and a V6 but i have always been a Big block big power guy so soon it will be time to head back to FL pick up the TH425 and finish what i started for revers rotation and get the biggest baddest big block i can afford in it make as much HP & torque as i can

quote Originally posted by engine man: well i toyed with the idea of a standard and a V6 but i have always been a Big block big power guy so soon it will be time to head back to FL pick up the TH425 and finish what i started for revers rotation and get the biggest baddest big block i can afford in it make as much HP & torque as i can

I have a TH425 for sale, Long Island, NY. Even has a brand new, never even filled with Dextron Converter.

thanks Tony but I have a thm 425 in FL and my car is down there so i need to go down and get every thing and finish biding the tranny with a flipped diff but the diff comes from the thm 325 but what i have found is the input shat to the 325 diff has the same spline as the thm 350 output shaft so i bought a out put shaft that fits a thm 400/425 with thm 350 splines now i just need to figure out how thick my adapter plate needs to be but i need to get what ever engine i am going to use to figure out where the main cap is that the axle will pass under

bump, any progress with this?

No i have been working on a 3.4 dohc fiero but when i get it done with all the bugs worked out i will get working on this i have the transmission and a diff from a turbo 325 and bought a output tailshaft that fits the diff and turbohydromatic 425 just gotta see how thick an adapter plate needs to be to mate the diff to the tranny and put it together and put it in a car

To all that consider the TH425 transmission for a longitudianal V8 application in a Fiero, just be aware that the weight is about 350 lbs. Add a SBC and the steel reinforcing members necessary for doing this engine swap and you could end up with a 1000 lb powertrain. Is this good? You decide.

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" THE BLACK PARALYZER" -87GT 3800SC Series III engine, ZZP Intercooler, 3.4" Pulley, N* TB, LS1 MAF, Flotech Exhaust Autolite 104's Custom CAI 4T65eHD w. custom axles, HP Tuners VCM Suite.
"THE COLUSSUS"
87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H
" ON THE LOOSE WITHOUT THE JUICE "

For a top performance sports car? Definitely too heavy. For a fun, sporty, strong hot rod for my dad to cruise in and maybe take to some shows? Seems perfect. I still don't quite trust that the F40 will handle the power we're going for. I know a couple guys are running them with V8s, but they built their cars to impress people, not to be beaten on. We're going to be pounding the car and our engine will be a 406 putting out somewhere north of 500 lb/ft and almost as much horsepower. I don't trust the F40 or the clutch to take that for long. I have no doubts about the th425 taking the abuse. Also, from what I can gather, the 425 only weighs around 250. That is about double the F40. I'll be running aluminum heads, intake, water pump, et cetera, so weight gain from the engine will be minimal. I think with proper thought put into the design and layout, along with strategic chopping of the sheet metal, I can get away without gaining too terribly much. Also, moving the battery and so on forward will help to keep the rear bias as reasonable as possible. Sure, its going to be less than a Ferrari for weight distribution and handling, but it should make for a very fun car.

quote Originally posted by TommyRocker: For a top performance sports car? Definitely too heavy. For a fun, sporty, strong hot rod for my dad to cruise in and maybe take to some shows? Seems perfect. I still don't quite trust that the F40 will handle the power we're going for. I know a couple guys are running them with V8s, but they built their cars to impress people, not to be beaten on. We're going to be pounding the car and our engine will be a 406 putting out somewhere north of 500 lb/ft and almost as much horsepower. I don't trust the F40 or the clutch to take that for long. I have no doubts about the th425 taking the abuse. Also, from what I can gather, the 425 only weighs around 250. That is about double the F40. I'll be running aluminum heads, intake, water pump, et cetera, so weight gain from the engine will be minimal. I think with proper thought put into the design and layout, along with strategic chopping of the sheet metal, I can get away without gaining too terribly much. Also, moving the battery and so on forward will help to keep the rear bias as reasonable as possible. Sure, its going to be less than a Ferrari for weight distribution and handling, but it should make for a very fun car.

I believe that you will get good weight distribution with the Longitudinal setup. As for the weight ;a guy that I know with an LT1 w TH425 put the trans on the scale and it weighed in at exactly 340 lbs. You've got to consider the weight of those stout axles as well. As you are also aware will also need a "cage frame" made of steel channel to hold that powertrain in place.
The LT1/TH425 combo is reliable (as the trans was designed for V8 power) and the combo is fast. You can beat on it without fear of drivetrain failure. You might want to check out the FDR on your trans as they came in different ratios IIRC most of the time with a 2.73.

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" THE BLACK PARALYZER" -87GT 3800SC Series III engine, ZZP Intercooler, 3.4" Pulley, N* TB, LS1 MAF, Flotech Exhaust Autolite 104's Custom CAI 4T65eHD w. custom axles, HP Tuners VCM Suite.
"THE COLUSSUS"
87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H
" ON THE LOOSE WITHOUT THE JUICE "

Why would it weigh more than double the TH400 it is based on?

quote Originally posted by TommyRocker: Why would it weigh more than double the TH400 it is based on?

Because the final drive is attached directly to the trans and its very heavy.....

I understand that, but 200 pounds heavy? wowee

to me it is how much heavier is it than a 4T60 e HD or one of the heavy duty FWD automatic transmission

quote Originally posted by engine man: to me it is how much heavier is it than a 4T60 e HD or one of the heavy duty FWD automatic transmission

According to several salvage yards that I contacted in the past, the weight of the 4T65eHD is approximately 200 lbs. but I am not sure if that included the torque converter weight. Using rough figures, that would make the TH425 in the range of 100 to 115lbs heavier but if you like the longitudinal arrangement, go with it. IIRC V8 Archie has some numbers on the weight differences between his transverse V8 swaps and the longitudinal swaps. Maybe he can post them for you.

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" THE BLACK PARALYZER" -87GT 3800SC Series III engine, ZZP Intercooler, 3.4" Pulley, N* TB, LS1 MAF, Flotech Exhaust Autolite 104's Custom CAI 4T65eHD w. custom axles, HP Tuners VCM Suite.
"THE COLUSSUS"
87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H
" ON THE LOOSE WITHOUT THE JUICE "

quote Originally posted by TommyRocker: Why would it weigh more than double the TH400 it is based on?

The additional case material to have the bellhousing off to the side, the chain drive setup (chain, sprockets, extra shaft length), the differential mounted on the end, and axles if they are installed during the weighing process.

The axles are negligible because you need axles with any trans you go with. So say we gain 300 pounds... we should still be able to come in below 3000, so we'll have a leg up on the vast majority of cars out there, plus we'll have 500 torques to get us moving. Ideal? No, but certainly an acceptable toy.