Has anyone done or have knowledge of an LT1 placed longitudinally?

I havent heard of one mostly because the LT-1 has a 1 peice rear main seal so you would have to adapt the flywheel to fit a GM longitudinal trans.

It HAS been done and I HAD a pic of the car but for the life of me, I can't find the pic.
The car was a GT painted a dark red if I recall correctly.

I'd bet the dark red ( burgandy ) example your thinking of was Joe Wynmans' LT1 powered GT.

I know it wasn't this one:



or this one:



David Breeze

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Pantera Rebody Kits

I found the pic and I believe you are right about Joe's car.

Well I geuss it has been done does anyone know how they adapted the flexplate?

What GM transmissions are useable in this configuration? I am aware of the Porche transmission option from BubaJoe's thread for the longitudinal Northstar, and of the option for the Audi 5000 from the Lambo Lounge, but what GM automatic transmissions are suitable and do they produce ahead of axle or behind axle installations?

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Daviero - 88 N* GT

Daviero - GM offered two, the TH325 and TH425. Both were originally oriented with the belt-drive to the rear of the engine. A few folks have flipped the differential on the TH425 in order to obtain reverse rotation. I have a rebuilt TH425, differential and axles out back in my shed. If you've heard of the turbo-hydramatic (TH) 350 and 400, the 325 and 425 are the front-wheel drive versions. GM used the TH425 in their 500 cu. in. Eldorado & Toronado ... and in the early-70's FWD motorhome. The TH325 was typically used in lighter-duty cars, such as 1980s Cadillacs ... had one in an '85 Eldorado. I do know a guy who stuffed a 455 Rocket in the back of his Fiero with a TH325 for 1/8-mile drag racing.

What modifications have to be made to the frame or cradle to put the Lt1 in longitudinally?

Joe Wynman used to be president of the Tri-State Fiero Club back in the mid 90's. I remember this Fiero well. Joe was working on a longitudinal swap with the Toronado TH -325 when he located and purchased this Fiero that was built by another club member who was a welder. At one time Joe sold Fiero parts and had a CD that included all build steps , drawings and complete instructions for this type of swap. I may still have Joe's phone number if you want to contact him and ask if he still has any of these CD.s. I haven't seen Joe on the Fiero scene for quite some time
What concerns me most about the longitudinal V8 swap is the weight and the precison that is required to build and position the cradle and the heavy Fiero that results. You also must use a transmisson not known for it's quick shifts and one that uses 30 yr old technology. I believe that V8 Archie may have some data on this as he always maintained that the transverse V8 swap was the way to go.

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87GT 3.4 Turbo- 0-60 5.2 seconds
2006 3800SC Series III swap in progress
Engine Controls, PCM goodies,
re-programming & odd electronics stuff
" I'M ON THE LOOSE WITHOUT THE JUICE "

[This message has been edited by Dennis LaGrua (edited 09-04-2007).]

Some questions for the longitudinal configuration using the TH325:
If the TH325 is the longitudinal equivalent to the TH350, then is it safe to assume there is aftermarket support for the TH325 as there is for the TH350?
Is this an exceptionally heavy transmission compared to the Caddi Northstar 4 spd 4T80e
What is the horizontal distance from the face of the bell housing to the axle centerline?
Does the "flipped" configuration (engine forward of the axle with reverse engine rotation) require the axle through the oil pan that I remember seeing somewhere?
How likely is it to find axles that will adapt to this transmission and to our hubs or would custom axles likely be required?

The specific option that interests me about this option is an inline Northstar, provided that the flex plate and bell housing adaptors can be sorted out too.

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Daviero - 88 N* GT

quote Originally posted by Daviero: Some questions for the longitudinal configuration using the TH325: If the TH325 is the longitudinal equivalent to the TH350, then is it safe to assume there is aftermarket support for the TH325 as there is for the TH350? Is this an exceptionally heavy transmission compared to the Caddi Northstar 4 spd 4T80e What is the horizontal distance from the face of the bell housing to the axle centerline? Does the "flipped" configuration (engine forward of the axle with reverse engine rotation) require the axle through the oil pan that I remember seeing somewhere? How likely is it to find axles that will adapt to this transmission and to our hubs or would custom axles likely be required? The specific option that interests me about this option is an inline Northstar, provided that the flex plate and bell housing adaptors can be sorted out too.

The TH-325 shares nothing in common with the TH-350. Rebuild parts can be found but it is a heavy inefficient transaxle built with 30 year old technology. This was from the family of trans used on the first front wheel drive car that GM built. . . If my memory serves me correctly a TH325 weighs something like 375 lbs. Couple this with even a 450 lb smallblock add a cage type reinforced cradle and you'll have over 800 lbs behind you. The 4T80 used with the Northstar is no lightweight either at 295 lbs. but the N* is a relatively light engine. I don't have the rest of the info as we are not involved in any longitudinal swaps.

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87GT 3.4 Turbo- 0-60 5.2 seconds
2006 3800SC Series III swap in progress
Engine Controls, PCM goodies,
re-programming & odd electronics stuff
" I'M ON THE LOOSE WITHOUT THE JUICE "

[This message has been edited by Dennis LaGrua (edited 09-05-2007).]

There seems to be a few confused issues.

Which "inline" trans is the 425/325 derived from? Doesn't really matter. In looking up parts, I've seen shared parts with the 200, 350 and 400. But to answer your question, yes, parts & service are available. Most trans overhaul shops are familiar with them. A complete major overhaul kit will run you @ $150. Factory service manuals are abundant on Ebay, and the company that sells overhaul books & parts has a very complete book on overhauling these units. A couple of different overhaulers have told me that the 4-speed version was the weakest, the 425 the strongest, and the 325 a good compromise of strength and weight.

Yes, the trans is heavy. The 425 reputedly heavier by 50 lbs than the 325. A lot of the weight is actually in the massive differential, which is positioned ahead of the axle centerline. Problem is a portion of the engine sets aft of the axle centerline. So you do wind up with a tail-heavy configuration. Does it matter? If you are going to autoX , forget it. If you are building a heavily powered, straightline racer ( isn't that what stoplight Indy's are ? ) you are in business. It will proably swap ends on you faster than a "normal" Fiero. But it is a family of transmissions that can handle any hp & torque you can dish out.

Reversed means that the engine/trans are mounted in the car with the trans forward and the engine aft. This is done to change the weight bias and shift it forward, "solving" all of the formentioned problems. One supposed method is to flip the differential, in order to make it rotate in the proper direction, after rotating the trans/engine. On the 325, this actually raises the axle centerline in relation to the engine. So this would lower your center of gravity,but it will also bring the axle further up into the bottom of the oiolpan, and there you may encounter problems. If you lay all this out on your work bench, it becomes apparent that if you could build a short tunnel, a few inches long, and had an adapter shaft made to bridge the tunnel, you could then move the differential enough to get the axle out of the way of interference, and maybe make this work. I have heard of one example done this way, but never seen it.

Does the axle pas thru the oilpan? Yes. If that bothers you, call someone who sells $3,500 adapter kits and use a transverse trans.

Will the 425/325 & a v8 fit without a frame stretch? Yes. You will need to stretch the aft end of the cradle, but it's easy to do. You will also have to cut out a portion of the trunk, and add a new reinforcing member between the strut towers. No "cage" is required.

David Breeze

When I looked into this several years ago, my plan was to ditch the stock diff in favor of a front 4x4 diff (toyota 4 runner) to:
1. aid in axle clearance when the diff is flipped and
2. move the axle centerline further from the trans and close to inline with cylinders 1/2 on the engine. This would put over 75% of the engine/tranny weight in front of the axle centerline. It would require a custom machining to cap the tranny and transfer the power from the splined shaft to the new diff.

The downside with this is that the toyota 4 runners came with 4.10 gears which was not the direction I wanted to go and the diff is probably not all that strong. The GM front diffs have the longer shaft on the wrong side to work unless they can be disassembled to make them shorter, but GM has 1 ton versions of the diff and several more gear ratio choises.

What other inline automatics have been successfully used? BubbaJoe has used the Porsche 5 spd so one would assume that the Porsche automatic would also be OK other than the length required? Also the Audi 5000. Any experience with any of these autos?

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Daviero - 88 N* GT

There is a thread at the kitcar forum, using the Chrysler 300 trans to longitudinally mount a GM engine.


Bob

I was looking at the chrysler transmission, it is basicly a flipped version of the porsche transmission, so you do have to flip the differential. If you don't have a problem stretching the frame, and aren't planning on running unholy amounts of power I don't see why that woudn't work.

Chris