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Looking for a Low-Budget Driveline Swap


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A while back I posted re: Dynaflow problems in my '56 Century. The more people I talk to, the more expensive the problem gets--latest rough quote at $2,800 for a rebuild.<P>From everything I've read in these forums, there is no bolt-in replacement for the Dynaflow/322 combo apart from some rare Olds Hydramatic that was made to fit when the Dynaflow factory burned. Not sure what year that was.<P>At any rate, I'm thinking of doing the unspeakable here in Buick-land--replacing the entire driveline with a SB Chevy, 4-sp AT, etc. I'm sure someone has done a similar swap--but is it possible on a budget? (I'm not skilled enough to do a whole frame swap.)<P>Can someone explain WHY the torque tube rearend cannot be left intact? Can the pinion and yoke be changed out to something compatible with an open driveshaft?<P>As always, any assistance is appreciated.

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Thanks for the explanation re: torque tube and thrust.<P>I take it that means that even if I were to replace all the original rear-end mounting points onto an open-driveshaft rear end, I'd have no way of controlling the fore-and-aft motion and would need another method of transferring that thrust to the frame. Is that correct?<P>Don't the two long arms that locate the rear end do enough thrust control?<P>Thanks again for you help.

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If you look at the mounting place for the strut rods that locate your rear axle ,you will note that they are attached to the torque tube. when you remove the torque tube , you lose your rear axle positioning and support. The only way to go to an open drive is to put in a late model rear end ,complete with the four link unit that holds it in position

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I obviously don't spend enough time under my car--forgot about the struts mounting to the torque tube!<P>Putting in a four-link doesn't sound all that easy. What frame mounting points need to be added? What original mounts can be used? I take it there is no "bolt-in" swap option.<P>Is there any way (is it safe?) to consider fabricating a mount that will allow continued use of the strut rods by transferring their load to the cross-member under the transmission? Assuming it is possible, can the struts alone do the job that the torque tube/strut combination was designed to do?<P>Thanks again.

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yeap. the entire rear suspension, including the two diagonal 'ladder bars' hangs off the back of the dynaflow. no way to save that setup without that tranny. no other tranny you could put in its place is designed to accept that kind of stress on its tail housing.<P>there is no point in using a chevy motor, it does not solve your rear suspension problems.<P>if you think you are not capable of doing a frame swap, i really dont think you want to tackle building a new ladder bar/panhard or 4 link setup. if you do, look at mid to late 60's chevy pickup trucks, they have a long ladder bar style setup that should be adaptable. have a competent welder/shop do the actual work... of course, switching to leaf springs is probably the easiest way to fix the suspension issue.<P>note: the 122 inch wheelbase of the 56 century is the same as the 71-76 riviera. if you are going to pay someone to change the engine, tranny, and entire rear suspension (meaning potential brake changes) as well as build a custom driveshaft AND get the pinion angles right, you just might want to consider paying them to replace the frame...<P>as far as getting an overdrive behind a buick motor, the th200r4 is fine when you pay to have it built up, but the 4l80e from big gm trucks (based on the th400) looks really beefy. (adapter plate and computer required)<P>BTW, it was the hydramatic factory that burned, IIRC.<BR><P>------------------<BR>allan<BR>--------------<BR>50 special, 455/th400<BR>64 stude gt hawk, 289/auto<BR>76 poncho GP, 400/th400

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You can't use the torque tube setup because:<P>On a torque tube car, the thrust from the rearend travels to the frame via torque tube/torque ball/dynaflow (transmission itself)/thrust pad (one of the transmission mounts)/transmission crossmember(that the dynaflow sits on)/frame.<P>On a non-torque tube setup (the vast majority of cars) the thrust travels from the rearend to the frame via either control arms connected from the frame to the rear end, or leaf springs.<P>An open driveshaft typically carries absolutely no force except torque (rotational). They are not designed to carry thrust at all. In fact, many have a slip joint to allow for slight fore-aft motion between the rear end and the frame of the car, given that the rear end is not really strictly fixed from fore-aft motion.<P>If you tried to retain the torque tube setup, I guess you could drive a few feet before the driveshaft was destroyed, followed by many other things...<P>Mark<p>[This message has been edited by Mark Schmerbeck (edited 02-04-2001).]

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A thought just occurred to me..<P>Would you be asking for trouble if you just swapped the coil springs for leaf springs, retained the original rear end, and somehow got a yoke adapted to the rear end minus the torque tube???<P>Seems to me this could be a low cost solution. But practical???<P>Mark

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Thanks for the comments, Mark. I would think that the leaf springs would be sufficient (they are for other cars, I think) if the perches were large enough and welded to the axle correctly. I did see something in Hot Rod a while back that used the original coil springs and used only the front half of a set of leaf springs as locating arms. It wasn't in a two-tonner, however.<P>I did toy with the option of transfering the load from the strut rods to frame rather than to the torque ball. Question is, how much load does the toque tube itself carry, and are those struts there merely for triangulation at the torgue tube/rear end joint? The struts are long, and I would suspect that under heavy acceleration they would flex quite a bit if used as the sole fore-aft locating points. Keep thinking!

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martens, check with Pete&Jake or one of the other street rod parts places. They have plenty of ladder bar style set ups that even have cross members and are relatively easy to install.<P>------------------<BR>buickfam@aol.com<BR>Life long Buick Fan.<BR>1965 Skylark H/T<BR>1965 Gran Sport Convertible<BR>1948 Chevy Pickup with 401 Buick.<BR>"Fan of anything that moves human beings"

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