Ok i went out and bought a turbo hydamatic 425 and am going to flip the differential so i can have the engine facing backward . the peice of steel will be 3/16 thick that will give me 5/16 inch of shaft engagement

pics!!!

you using the street dreams kit?

theres is for the thm325 gota make my owen will go get some steel on tuseday may be before work. do any of you know if how much i can have the axles running forward to the tranny from the wheels

Now that you have the trans, pop out the very short axle stub, and the intermediate axle from the diff and swap them, you'll have to do this when you flip the diff, see if the axles fit in the opposite sides. this is where I think some others were having some concern and maybe having to get custom axles made.

[This message has been edited by AmericanMuscle (edited 11-29-2009).]

I think that they will fit no problem just you need to make some sort of retainer for the short one i looks like there is a bolt in the midle of the short side that retains it

yeah the street dreams kit is for 325 and 325-4l. i misread.

Can not be done on a 425 reasonably. Lhs and Rhs Axle diameters are different, along with axle retainers. Then diff will be well into the engine block. Then oiling will be wrong, stub shaft is not long enough to support a plate unless you weld ears on the alluminum trans case..etc. Best way would be gears instead of chain but even still the reliablilty lost will not be gained back by the benifit of weight shift AND IF you are that concerned about weight why even consider a th425 in the first place!

Been there...and after a couple hundred dollars wasted I was happy when the scrap metal guy came by and took the th425 away. sry all is IMO

Pete

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quote Originally posted by PBJ: Can not be done on a 425 reasonably. Lhs and Rhs Axle diameters are different, along with axle retainers. Then diff will be well into the engine block. Then oiling will be wrong, stub shaft is not long enough to support a plate unless you weld ears on the alluminum trans case..etc. Best way would be gears instead of chain but even still the reliablilty lost will not be gained back by the benifit of weight shift AND IF you are that concerned about weight why even consider a th425 in the first place! Been there...and after a couple hundred dollars wasted I was happy when the scrap metal guy came by and took the th425 away. sry all is IMO Pete

Did you end up using the th325 or scratch the project all together?

well if thats the case then i will just have to move the engine forward as far as posible with the engine facing forward and move as many things to the front of the car . I will check out the axle being a different size by tuseday and if they are i will be forced into facing the engine forward.

[This message has been edited by engine man (edited 11-30-2009).]

Keep in mind the Pontiac timing cover is prolly 3 inches thick and you got the dampener and pulley that have to clear that.

ya i am just thinking if i dont do a reverse rotation how much can i get the engine & tranny forward

[This message has been edited by engine man (edited 11-30-2009).]

quote Originally posted by engine man: ya i am just thinking if i dont do a reverse rotation how much can i get the engine & tranny forward

I was watching Xtreme 4x4 the other day and they were making a dune buggy and they had a rear facing engine and they used an 89 Acura Integra motor because it is a reverse rotation engine. I don't know that you would want a 1.8L 4 cylinder engine mounted to a TH-425 but it would be going the right way.

that is an idea buy a cam that lets the engine run in the reverse rotation

[This message has been edited by engine man (edited 12-01-2009).]

this is a link to cardealers gear drive reverse rotation tranny i would love to do it this way i think that you need to change a few parts in the tranny that are made to free wheel one way and lock the other but they should be easy swap with th400 parts
https://www.fiero.nl/forum/A...040223-1-031409.html

[This message has been edited by engine man (edited 12-01-2009).]

quote Originally posted by engine man: this is a link to cardealers gear drive reverse rotation tranny i would love to do it this way i think that you need to change a few parts in the tranny that are made to free wheel one way and lock the other but they should be easy swap with th400 parts https://www.fiero.nl/forum/A...040223-1-031409.html

I think the gear thing would be a little work, you'd need to support those intermediate gears on both sides, considering the torque of a v8 or any engine for that matter.

[This message has been edited by AmericanMuscle (edited 12-01-2009).]

I will be pulling the carrier out to see what needs to be done but to flip it it looks like i might have to get one axle turned down and the other bushed up no big deal then i will make a plate out of 3/16 thick steel to do the flip bigest problem i see is the dip stick

ok what i found out is that one axle will need to be bushed up in the bearing area and one turned down to fit but the splines are the same . the other thing that needs to be changed is the axle gears with the splines so you can use the retainer bolt on the shot side axle.

quote Originally posted by engine man: ok what i found out is that one axle will need to be bushed up in the bearing area and one turned down to fit but the splines are the same . the other thing that needs to be changed is the axle gears with the splines so you can use the retainer bolt on the shot side axle.

Go for it, if you have the resources and enginuity. Id likr to see some one make the th425 work, Id get the engine and bolt it up before starting to alter the trans though.

my bigest problem right now is getting the dam ring gear out i pulled the caps but for some reason it wont come all the way out so i can take it apart and switch the parts like i need to

Use a BFH j/k . dunno never had one apart

IMO you need to reconsider your 3/16 plate. There is a lot of bolts holding that diff to the case for a reason. Also the stub shaft into the trans only goes in an inch so the thicker the plate the less stub has to grab. Just there is more to consider then the axles here unless your bolting a low hp engine up. IMO your only option is to have the trans case modified/welded with new alluminum ears to match the flipped diff.....anyway you look at you end up at the same place I did....why! Cause it will never handle well with all that weight back there reverse rotation or not. Then you gotta look into the engine oiling, oil pan and oil pick up cause a 10 or 11 sec car has all the oil pushed/forced to what is now the frt of the mtr, but your oil pick up is at the back.

Pete

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quote the other way i was thinking is puting a th400 short tail shaft on it then using like a s10 4wheel drive front diff conected by an H bar used in boats just would have to make brakets to hold the diff

i hear people putting Jeep front axles and stuff on the S10s.
you could always use Jeep front end stuff. just an idea. so your not so limited

PBJ first you have to remember that a cadillac weigh's 5000 Lbs and a fiero weighs 2600 lbs if it dint strip out with only 3/16 more holding it i doubt it will strip out in a 2600 pound car or 2900 pound car. there is a big differance in handling by reverse mount you now have the weight in front of the back axle and not behind it acting like a pendulum + the lever affect. you sound like some one who is mad and dont want some one to do some thing you gave up on . I am going to make mine a shorty out put shaft the put a unerversal joint hooke to a differential out of like a S10 4wheel drive i will need to look at differentials to see what has axle's like the fiero uses

Engineman, I think PBJ means well here, he as well as I don't want to see anyone fail at a project like this, I have no first hand experience at this but he does and is only trying to warn you. you'd think that after 22 years someone would have done this already but we can't seem to find a successful 425 reverse rotated setup. Mind you Im behind you all the way and would like to see you do it, just make sure you know all your options.

I think that fliping the thm 425 differntial can be done but you have to pay way to much for gears or pos thats why i like the option of making it a shortie shaft output then i can hook any differential i want from a ford 8,5 to a quick change.

[This message has been edited by engine man (edited 12-03-2009).]

quote Originally posted by engine man: you sound like some one who is mad and dont want some one to do some thing you gave up on

Wow now this is an interesting statement on a forum. I was trying to communicate my personal hands on experience that I believe very few people on the forum have with a th425....not to have you fail. I am not going to off topic here so..best of luck.

Pete

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well i went to the junk yard to measure up some front differentials out of some 4 wheel drives and it looks like it is 11 inches from the center of the u joint to the center of the axle and if we add another 3 inches for the tranny shortie shaft. the back of the tranny to the center of the axle should be 30 inches . Ok i asking some one with there engine out measure 1 foot up from the bottom of the firewall then 1 foot up measure back to the center of the axle i think that will be about 27 inches that would make me have a 3 inch angle back. I think thats doable do you think thats to much angle

Ok sorry I can't STFU. DO you want me to tell you the problem with your latest idea (2 right of the top of my head)...cause I can...but not cause I am mad....but because I do know some "stuff"

I better go back to the boating forum

Pete

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Hmm i made no reply to your last post due to i was sory i had posted what i did. It seems folks are not giving any one a chance but now your back ready to say you could bash the new idea so it kinda looks like your negative on the whole thing .I hope you have some good ideas but maybe you are just sick of the thm425 i dont know . pleas if you want to just post negative then pleas dont post i would rather hear ideas than negativity.

The divorced diff is a great Idea even thought of it myself but I think you'd have to stretch the frame . The diff would be to far back, you say 3 inches off center axle line, That angle depends on the length of the axles, if their really short axles (which I think they will be due to the size of the trans) I would think the angles will be to much, if the axles were 3 feet long it'ed be no biggy. What about cutting the firewall ? and boxing in a doghouse? it would use up some of the space behind the seats but would give you the clearance you need. I once installed a big block 427 chev into a 79 merc capri, cut the firewall and set the motor back about a foot, the built a frame and doghouse around the back of the motor, It was kept under the dash but I had to move my gas pedal to the left a bit. I dont know about the Fiero space frame and how much cutting would effect it, but I think youd only need enough to clear the back cover.
Edit: then again I forgot about the gas tank

[This message has been edited by AmericanMuscle (edited 12-03-2009).]

Does anyone have a picture of a THM-325 (with engine) mounted on a Fiero cradle? I'm having a hard time visualizing how the differential and axles clear the oil pan. All the pics I found in the archive don't show this clearly.

The idea was very clever at the time, but GM (and everybody else) eventually decided to go transverse with FWD and this type of transmission disappeared. As a consequence, most of us have never seen a THM-325/THM-425