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Discussion Starter · #1 ·
I need some input here folks, although it may be too late. I got the measuring all done, kinda, for the drive shaft length on my V-6/T-5 mod. I called the local reputable shaft shop and this is my predicament. The universal joints that go into the drive shaft tube may have to be machined down in length to be able to achieve the shortened length of the shaft to be put in between the T-5 and the torque tube. Here's the question: With the drive shaft about 7-9 inches long, overall length, and the alignment really, really close, and knowing the shaft will move in and out of the tail shaft housing about 1/4", will it work? I think I'll have about a 2" tube between the u-joints. I hope this is descriptive enough for a response.

Ron
 

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You will break U-joints under moderate power, or when downshifting with that set-up. There are two solutions. First, go with a different transmission with a shorter tail shaft. Second, go with a different differential/rear suspension set-up.

The differential/rear suspension swap will be the better of the two because you'll get a differential that will hold up to more torque. That way you get rid of the torque tube set-up and use a much longer drive shaft. Also, the Toyota truck differential is very strong and you can get many different ratios for it.

Travis did a real neat Toyota truck "transplant" and had posted much of the information here on opelgt.com. If you follow along with what Travis did, the differential swap will be easier than the V6 engine swap.
 

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Discussion Starter · #3 ·
Well, that didn't make my day at all!!! I've already got $1500 in it for the ZF posi-traction, plus the $200 for the drive shaft mod, not counting the time to totally strip, derust, and paint the whole assembly. I trust your expertise on the subject, but I just can't justify tossing that much money out the window without trying this setup. If it breaks, then I'll go back to the drawing board, again!!! Thanx for the input, I'll have to be careful with throttle application when I get it finished and on the road. But first things first, I have to finish the transplant, Phase III is still in progress.

Ron
 

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I guess I wasn't strong enough in my "suggestion" that you should change the rear-end. It isn't a matter of "if it breaks"... it is just a matter of when. Then, when it breaks, if you're lucky, the rear U-joint will break and the drive shaft will merely fall out on the road leaving you stranded. If, on the other hand, the transmission side breaks, then you will be left with the rest attached to the torque tube flailing around at say 3000 RPM... it won't be pretty.

Sell the stuff you've got while it is all prep'ed and you can get back most of what you've invested. If do it right the first time you'll save money in the long run... and save the "grief".
 

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Discussion Starter · #5 · (Edited)
Well, you got my curiosity up, so I called the tech at the driveline shop and voiced your opinion that the u-joints would break. He was of the opinion that the pinion gear would go before the u-joints. I don't want to start a pi$$ing contest here, nobody wins and everyone gets wet, so here's what I propose to do: I'll install the modified shaft; take an incidence reading of the angle with the car on the ground; jack it up until the rear-end is hanging on the shocks, take another reading; pull the springs and shocks and jack it up 'til the axle hits the bumpers and take a final reading. Also I'll get the azimuth of misalignment to be vectored in also. Then I'll post the readings with corrected angles, ie., the car on the ground vice the car in the air. I am just struck with the thought that early Jaguars and new Corvettes have IRS with u-joints on both axle ends and I believe their deflection angles would be greater than what I may have on the GT, plus they put out much more horsepower. But let's put this to rest for the time being.

Ron
 

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my shortened driveshaft seams to work great. no problems what soever. and i have been all up on the accelerator, and i believe that the pinion would go before the universals. just gettin my two cents in
 

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a 9 1/2" driveshaft will survive. If you carefully read the origianal post... or if I was reading it correctly... it says the driveshaft is about 2" between the U-Joints. Two inches will put a severe angle on the U-joint and it will break. The only way to get something with severe angles and much torque is with CV joints... and I don't think 2" would be enough to get CV joints in there instead of U-Joints.
 

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The problem with a very very short dirveshaft (2") is not because the drive shaft moves up and down. Rather, most of the problem is that the torque tube is also a suspension member. So as the suspension moves up and down, the angle of the input to the torque tube changes. The angle of the torque tube also moves a little bit sideways under torque.

So, it all adds up... the tail shaft moving a little under torque from the engine... the torque in the "squat" during acceleration... side movement of the torque tube itself from torque... sideways angular change during cornering... all combine toghther and everything ends up trying to wind around itself... and the U-joints give up.
 

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Discussion Starter · #12 ·
Maybe I should have clarified in the original post that I will have about two inches of tube between the welds and that center to center at the u-joints, it will be approximately 4 1/2" . That was the original concern a really short drive shaft.

Ron
 

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correction: my driveshaft isn't 91/2 inches it's 61/2 inches which makes sense because if you're using fuel injection the engine and transmission can sit back like another 1 1/2 inches because it has no distributor. my motor has a distrubutor so it had to sit farther forward therefore fixing our messup
 

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Discussion Starter · #15 ·
I appreciate all the inputs, that's the reason I started this thread. I am concerned about this driveshaft. Understand this mod was not taken lightly, but with a lot of questions asking and after seeing it could be done, I took the task on. I could have rebuilt the 1.9 that took out a bearing, but then I'd still have a 1.9. During this mod, I am replacing or refurbishing everything, with the exception of the engine and transmission. They have already been proven to operate as advertised. The complete rear-end assembly has been totally rebuilt with Gil's best stuff. The differential was rebuilt by the best rear-end shop available and any parts that were suspect were replaced. The front end will also get the teardown, strip, derust and repaint. The brakes are going to end up being completely redone with new lines, hoses, and hardware. I've been working on this for over a year, and finally getting to the point where I can see the engine running in a month or so installed in the car. By the end of the week, I should have the shaft installed, if the new u-joint from Gil arrives at the shop tomorrow. Then I'll take the angle readings, and we can start this whole mess again. The exhaust system will have to wait until Monday after the Thunderboats this weekend. It's been one thing at a time, fully focused to get it done and looking good. Now, there is light at the end of the tunnel, but it's one hell of a long tunnel!!!

Ron
 

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Ron,

Maybe Bob had a good suggestion that went unheard. If you have 2 inches of straight tube BETWEEN each U-joint, don't you have enough room for a CV joint in place of each u-joint, welded back to back?

Or, maybe ask your drive-line shop if they have a beefier u-joint? It would seem that the Opel u-joints could be replaced with some kind of truck unit, or something from a mid-sixties muscle car, which would at least be stronger than the standard Opel joint.
 

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I want to make a request in this forum since it has to do with drive shafts. Sorry namba for cutting in, so to speak. The PO of my 69GT had a no torque tube drive shaft in pass. compartment when I bought it, it's a solid style 2-piece assy. Has anyone ever gotten a reply from the Opel Junkyard in KY for anything? I sent for info on a stock $20 shaft they have listed, no joy yet on it. I want to get all my puzzle pieces together before I play, you know how it is.
Thanks, Barry.
 

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Discussion Starter · #18 · (Edited)
Keith, the front u-joint is from a 92 S-10, the rear is a new Opel u-joint from Gil. I can't use anything larger up front than the S-10, it's wider than the Opel by 1/4", and almost hits the tunnel walls, and I can't go larger than Opel in the rear because of the hook-up to the shaft inside the torque tube. I can understand it would be testy with only one u-joint in the drive line, but with two, it may still be iffy. This is a good OE & T, Operational Evaluation and Testing. I'm not knocking anyone and their opinion about this. I am concerned that it may not work. If it doesn't, then I'll have saved others the same problem and possibly come up with a fix. CV joints, maybe off a large FWD GM may be required. Here's the old tried and true statement, "If it ain't broke, don't fix it". My follow-on "if it does break, fix it better". But I will keep the group informed as how it goes. This is important enough to get the word out. I know of at least one other using the same engine/tranny combo I've got, there may be more out there. It may be that a different tranny is needed. Hard to say. Thanks for the input, I'm not so thick skinned I don't appreciate all the responses and I do take them into consideration. Say Hi to the family for me. Tell them I'm the long haired hippy type at the picnic.

Ron
 

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Old Hippie said:
Has anyone ever gotten a reply from the Opel Junkyard in KY for anything? Thanks, Barry.
Barry,

I've gotten a couple of parts from Opel Junkyard recently without any problems. I've contacted (David Ponder)via email, was quoted a price and availability, send my money order, and had the part within a week.
Maybe he doesn't have what you are looking for?
 

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I hope your wrong, but ya kinda expect a "can't help ya" letter. I don't want to rob my 71 of any parts just yet.
PS: hope you folks survive the hurricane. I 'm from So.Jersey origionally and my mom and brothers still live there. Stay dry!
 
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