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  1. #1
    Might as well be part of the furniture.
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    Propshaft dilema

    I actually had a bit of a go at the T today.

    Fitted the engine mounts that I had made with the engine set as low as I could before the starter motor hit the chassis so about 10mm clearance.

    I had to take a small tab off the 727 gearbox so it would miss the steering box by about 5mm, basically everything is "just in" I'm hoping that, due to the use of polybushes in the engine mounts and the gearbox mount, there will be minimal movement, HOWEVER!!!!!!!! due to not thinking too far ahead I now have a situation where the gearbox tailshaft is lower than the diff pinion and very slightly to one side.

    The distance from the end of the gearbox splines to the pinion face is 300mm, the diff pinion centre is 45mm higher than the centre of the gearbox splines and offset to the right by approximately 20mm. The Diff is a jag unit and is solidly mounted to the chassis.

    I have thought of four options:

    1) Leave as is and hope for the best and keep fingers crossed that I don't knock out the uj's every few thousand miles.

    2) Lower the Diff by 45mm via a plate below the mounting point and extend the torque straps, use longer diff bolts and modify the handbrake mechanism.

    3) Lift the engine up by 45mm which should lift the box by the same amount. however this would mean the engine would be even higher than the radiator than it already is and I already thought it was too high at the moment. The rocker covers are higher than the front scuttle. The original build was to have a rover 3.5 in it but I bought it less engine and box so I'm fitting a 383 mopar and torqueflight box which don't quite fit the width of the chassis rails and I'm not altering those.

    4) Leave as is and possibly use two rubber doughnuts one front and one rear. I need a prop making anyway so whatever would work is fine.

    I really don't want to lift the engine any higher if possible, one because I have only just had the mounts fabricated and I would have done them differently if I was going down that route and also I'm not sure an engine high up in a T is aesthetically pleasing bearing in mind aesthetics is a major part of a rod, also taking into account that the engine will be running twin four barrels on a high rise manifold with 9" K&N filters so fairly tall anyway.

    So any other ideas that might sort things or if not what would people suggest is the best option.

    As an aside I looked at T images and very few have the engine rocker covers higher than the front scuttle, I just can't see how I can get the engine any lower with the chassis constraints and even if I did it would make the misalignment even greater.
    Last edited by stilltrying; 26-02-17 at 06:17 PM. Reason: number of potions increased

  2. #2
    Might as well be part of the furniture.
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    With the solid mount diff you do not have to worry about UJ bind you get with suspension movement. Can you set it up on the bench to check if they bind? You can do the 45mm offset flat on the bench just by drawing a few lines. This is not uncommon with Jag IRS on Ts and mine has a 94" wheelbase so it shortish.

    Pics would help.

    You can just make out the offset I have with mine, its quite a lot. I would not worry about the 20mm, mines around that side to side. Also my prop is 300mm between the Crts of the JUs.










    Trying to find a pic of the prop installed.
    Last edited by fad15; 26-02-17 at 08:42 PM.

  3. #3
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    Had a thought. Check the angle of your drive shafts at ful suspension travel and see what angle they can go to. You will be surprised.

  4. #4
    Might as well be part of the furniture.
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    The drive shafts did not bind at this angle, when we bled the brakes. Hope some of this helps.
    G




    Last edited by fad15; 26-02-17 at 08:59 PM.

  5. #5
    REV JIM RACING.
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    That is a sweet car gerry.

  6. #6
    Might as well be part of the furniture.
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    I have the same 'problem' with my T n that with tall tyres and low engine box the prop runs uphill to the diff. This is compounded on mine by a two piece prop meaning the rear section is quite short and steep . This is where you get into operating angles and how they reduce the life of u/js. I explored all the tech and my operating angles reduce teh u/jj life expectancy to only 10% !! However this works out in driving hours to about 4 years based on 10k a year .

    As mentiones side offset is common and needed .

  7. #7
    Might as well be part of the furniture.
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    Quote Originally Posted by Torment View Post
    That is a sweet car gerry.
    Sorry for all the posts but I kept thinking how I could show you its probably not a problem
    Gerry

  8. #8
    Might as well be part of the furniture.
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    Glad I'm not alone.
    My prop also runs uphill to the diff.
    Can't do any thing about the mounting height of the engine without major surgery as the autobox is almost touching the bodywork.

  9. #9
    Might as well be part of the furniture.
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    Cheers everyone, it puts my mind at rest, I'll go with what it is and have the prop fabricated as per normal. My initial thought was that the prop will be turning about 3.5 times the speed of the driveshafts and people do get a bit anal about the box angle been 3 degrees downward sloping and the diff sloping upwards the same amount of degrees etc. Off set wasn't really a concern as many cars don't have a central pinion but off set to one side, it was just the sloping upwards on a short prop that sort of gave me a little concern.

    Gerry you really need to get that thing on the road, I would have said finished but they never are finished.

    Kev 10% life expectancy is fine by me, will probably only do 2-3K a year.

    Phil, although on your rod you could lift the engine and box with a little floor surgery it would still look sweet, on the T my engine rocker covers are already higher than the front scuttle so any more height would not look great in my view, os knowing you have been driving around in yours the way it is is reassuring.

  10. #10
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    Delving really deep into my (admittedly ageing) memory, I seem to recall an article in a US magazine that dealt with propshaft angles and the bottom line was that the prop angle is not the factor to consider but what they called 'phasing' the prop shaft.

    Basically they said that the angle of the shaft was of no real importance as long as the angle of the output from the box was parallel with the flange of the diff. That should work in both horizontal (if the diff is not central in the frame compared to the output shaft of the box) or vertical plane where one is higher than the other. As long as both ends operate at the same relative angle the UJ's are not fighting against each other. Plenty of production cars (and loads of trucks) use this principle.

    Hopefully my basic interpretation makes some sort of sense. If necessary I could scrribble something out and scan it.

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