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Thread: Tranny rumor

  1. #1
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    Tranny rumor

    OK I have just found out that you can mount a 350 engine into a none stretched fiero longitudally connected with an Oldsmobile Tornado tranny. Well I have gone nuts looking for more info and I can not find a thing. If it can be done what year?, how much horsepower?, and how many speeds?, also what mods are needed. Thanks.

  2. #2
    Senior Member rodrieguz's Avatar
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    Re:Tranny rumor

    That's not a rumor, It's been done plenty of times. The toronado trans is bullet brooof it will handle just about any hp.
    It only comes In auto though no manuel trans. You can use any trans out of a toronado , riviera , or eldorado. Mine is out of a 79 eldo.

    th425 th325, and th325-4l are all the trans that can be used.

  3. #3
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    Re:Tranny rumor

    I think the first th425 was in 1963 to 78 they could handle any thing you could build hp wise the th325 in 79 was for less hp but still reliable 3 spd autos. the th325-4l was a 4 spd auto but less reliable than the earlier trans. The motor sets higher so you may need to rework rear motor cover to clear.
    Gene

  4. #4
    Moderator FunnyWheels's Avatar
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    Re:Tranny rumor

    Longitudinal engine swap

    Information on the longitudinal engine swap for the Fiero chassis using a Riviera type automatic transaxle. Jon at Fiero Addiction has put together some information on the conversion. I copied that information for you and here is his post.

    Jon describes as much detail as possible, and the way he did it. Please confirm any info on his site before trying to use it, it is possible that he has made modifications in the process that could be of benefit to you and prevent some mistakes. The type of engine can vary of course, most common are the Chevy small block V8, Buick-Olds-Pontiac V8 (BOP) and the Buick V6. Jon chose a 5.7-liter small block Chevy V8 because they are cheap and readily available. There are also at least two different transmissions that can be used. The TH425 (three speed) was used in the Buick Riviera, Olds Toronado, and Cadillac El Dorado from '66-'78. The TH325-4L (four speed) was used in the same cars from '79-'85. Jon selected a TH325-4L four-speed auto.

    The engine can be mounted with the pulleys facing the front of the car, or they can face the rear of the car. If the engine pulleys face the rear, the installation will be referred to as 'reverse rotation'. Jonís was done in standard rotation. If you still need more info after reading this page, feel free to email him. You can also try to contact Greg at Fiero Concepts,100 W. Wonder St. Wildwood, FL 34785, (352)-748-7033. He has information on this type of swap and can introduce you to the reverse rotation swap.

    Engine/Trans Adapter.

    Both the TH425 and TH325-4L have the B-O-P bolt pattern. If you are using a B-O-P engine, that's fine, but for anything else, you will need an adapter. You can buy a BOP-Chevy adapter for about $55, TCI part# 230000, but they are easy to make. Take rubbings of the engine and the trans on stiff paper to make your own. Overlap the two, and make an outline that covered both. The dowel pins and the two lower holes line up perfectly. Cut it out, double-check, and then transferred it to 1/4" steel plate, cut it out, drill the holes and your done. You will need a 9/16" drill bit for the dowel holes. The torque converter also needs to be spaced ľ inch away from the crank to make sure it fully engages in the trans pump. This can be done by simply stacking washers and tack welding them to either the flex plate of the converter. A standard GM automatic flex plate can be used. The oil filter will need to be relocated. Use a standard relocate kit and added two 45deg fittings for clearance. The oil pan will need to be modified to allow clearance for the RH axle to pass under. Itís the same mod needed for a S-10 4x4 V8 conversion, for which oil pans are available. Use the stock oil pan and moved the bottom up to where the internal baffle is located. The axle that goes under the engine needs to be supported. It has a bearing at the end with a two-hole bracket. Modify the bracket so it will bolt to the unused side mount on the engine block. A 4.3-liter V6 would require the same work on to the cradle.

    Cradle Modifications

    Start by removing the engine cradle from the Fiero, and removing the stock engine and trans from the cradle. Set the cradle on the shop floor and draw a diagram with measurements from various points. The cradle will be cut apart, and if it is not welded back together with the correct alignment, it may not even fit back in the Fiero. After the drawings were complete, Remove the rear cross member from the side rails and discarded it. Set the engine/trans combination on the floor and positioned it so that the axles were directly in line with the lower ball joints on the cradle. Place marks on the cradle where the Fiero axles were before removal of the Fiero trans. Position the engine side to side so that the axle shafts would both be exactly the same length. Then make sure the cradle and the transmission pan were sitting flat on the floor, and start making a new extended rear cross member. Use rectangular tubing laid flat on the floor. After that is done, Make steel mounts to bolt to the rear of the trans and extend down toward the cross member. They are made of 5/16" steel plate, and heavily gusseted. Design them to utilize a round rubber or urethane bushings above and below the cross member. Then move around to the front. Start by making a horseshoe shaped mount that bolts to the front of the engine block with four 3/8" bolts. Weld a piece of angle iron to the rear of the front cross member to meet the engine mount, again with space for bushings. These mounts were wide enough to use two bolts about 4" apart. Everything needs to be gusseted to provide strength. That is it for the engine mounts. The tie rod mounts should be removed and discarded as part of the rear cross member will need to be replaced. There is no way to make them fit where they were, here is the trick. The spindles, calipers, tie rods, etc. will be swapped left to right. This puts the tie rods in front of the axle. A new cross member needs to be fabricated to mount the inner joints to. They should be spaced the same distance apart as they were originally, and at the same height.

    Body/Chassis Modifications

    This setup as described will fit within the stock Fiero body panels with the exception of the rear hood. Depending on the type of induction system and engine you choose, it may even fit under the hood. An 86 TPI required hood modification, even with a Countach body. There is absolutely no chance of retaining the trunk. What space isn't occupied by the trans, will be filled with exhaust pipes. If the trans is installed for reverse rotation, the trunk may possibly be retained. Due to the large increase in rear weight, the springs need to be upgraded. Chose to use a coil-over conversion from Held Motorsports with 350lb springs. The coil-over shocks allow ride height adjustment, and just about any spring rate you want.

    Exhaust

    The exhaust system is entirely custom made. Make the headers using a Heddman weld-up kit. Also have coated with aluminum and wrapped with Thermotec fiberglass tape. The Muffler of choice is a Dynomax replacement for a Buick Grand National. It is a cross flow design with dual inlets and outlets. Everything is connected with 2.25" mandrel-bent aluminized pipe, and tipped with Monza dual chrome outlets.

    The Reverse Rotation Option

    After Jon had already started his conversion, he found out that it could be done differently to better distribute the weight. By rotating the entire engine/trans 180 deg, you can get a lot more of the weight in front of the rear axle. The differential housing needs to be rotated 180 deg to an upside-down position. This also places the pinion shaft below the axle centerline, effectively lowering the engine. Jon has never done a swap this way, so he can only speculate what changes must be made. First off, the tie rods can probably stay where they are. In addition, the trunk may be able to be retained, or at least more of it. He would expect that the oil pan modification would be more extensive. If Jon were to do another longitudinal swap, he would definitely do a reverse rotation due to the weight distribution advantages. Using a V6 would also help weight distribution in a reverse rotation swap.

    Note: There are Gear drive set ups for motor homes that can be used in a reverse rotation installation that do not involve flipping the differential. I would look into those options as well.

    Regards,

    Dave

    If you're not confused, you're not paying attention.

  5. #5
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    Re:Tranny rumor

    Thanks for the info .

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