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  1. #461
    Join Date
    Jul 2012
    Location
    NW England
    Posts
    664
    Hi Aaron

    Thanks for the picture, think i understand a little better now, if I recall I did mention that I may not understand completely what is going on!

    But now your gearbox issue, it never rains does it?
    If the output shaft is turning with the input when neutral selected that would imply that the bearing between the input and output shafts is jammed, hence acting as one shaft, when you engage a gear you now have two forces trying to turn the output shaft (at different speeds) so it won't turn at all.

    Obviously I'm not familiar with your gearbox but it sounds as though clamping the front cover up is putting a force on the input shaft through to the output shaft. What happens if you back off the bolts holding the input shaft (just a bit at a time)? Does the shaft turn more freely (with the 'box in neutral)?

  2. #462
    Join Date
    Feb 2011
    Location
    Northampton
    Age
    42
    Posts
    4,687
    You're not wrong about it raining - in the same day I spent close to £400 on glasses, hit a pot hole in the OHs MINI and a front coil spring snapped in two, and the rear view mirror in the BMW dropped off the windscreen when I was cleaning it!

    Anyway, wanted to say thanks - armed with what you said ringing in my ears I loosened the bolts a turn or so and noticed that the front cover 'popped' off the gearbox a couple of mm, which told me two things; 1) you were probably right, and 2) the tube of RTV I found in my workbench clearly isn't much good anymore!

    The input shaft still seemed to be jammed to the output shaft, but with the cover loose it would shift through the gears at least. I pulled the front cover off completely and jiggled the input shaft while shifting from 3rd to 4th to 3rd and all of a sudden the gearbox was properly in neutral. Success!

    Popped the front cover back on (with no sealant as I need to buy some more) and did the bolts up and it still shifts, still free in neutral, goes into gear etc. I'm not sure what I'd 'pinched' but it clearly had the gearbox stuck in gear (4th, maybe, I think).

    Breathed a huge sigh of relief and came in for some dinner.. and to order some new RTV.

    Thanks!!
    My DeDion build diary..
    Hon Sec of the Digidash branch of the Unpopular Kit Car Design club

  3. #463
    Join Date
    Jul 2012
    Location
    NW England
    Posts
    664
    Quote Originally Posted by aaronjb View Post
    You're not wrong about it raining - in the same day I spent close to £400 on glasses, hit a pot hole in the OHs MINI and a front coil spring snapped in two, and the rear view mirror in the BMW dropped off the windscreen when I was cleaning it!

    Anyway, wanted to say thanks - armed with what you said ringing in my ears I loosened the bolts a turn or so and noticed that the front cover 'popped' off the gearbox a couple of mm, which told me two things; 1) you were probably right, and 2) the tube of RTV I found in my workbench clearly isn't much good anymore!

    The input shaft still seemed to be jammed to the output shaft, but with the cover loose it would shift through the gears at least. I pulled the front cover off completely and jiggled the input shaft while shifting from 3rd to 4th to 3rd and all of a sudden the gearbox was properly in neutral. Success!

    Popped the front cover back on (with no sealant as I need to buy some more) and did the bolts up and it still shifts, still free in neutral, goes into gear etc. I'm not sure what I'd 'pinched' but it clearly had the gearbox stuck in gear (4th, maybe, I think).

    Breathed a huge sigh of relief and came in for some dinner.. and to order some new RTV.

    Thanks!!
    Good to hear Aaron, at least the rain stopped for a while!

  4. #464
    Join Date
    Feb 2011
    Location
    Northampton
    Age
    42
    Posts
    4,687
    Here's hoping!

    I took delivery of the RM-130 T-56 index plate last week (https://www.holley.com/products/driv...s/parts/RM-130) which obviates the need to remove the gearbox end casing; it has up-sides and down-sides but I think it will be "good enough"

    The obvious down-side is that I'm not checking the actual gearbox and manufacturing tolerances mean I am working off an unknown. In other words, I'm just trusting that Holley (who I think own QuickTime now) can put the dowels in the exact same spot as the gearbox.

    However, I think that is outweighed by the fact that:
    1) My gearbox has an enormous 'snout' which makes getting a stable indicator base on the crank end or flywheel and then snaked up through the snout essentially impossible (IIRC GM gearboxes have a shorter/no snout)
    2) The end of the bell housing is so full of holes, making parallelism checks very difficult, too.

    I'll dig up some pictures but bolting the RM-130 plate up and checking with a nice, stable, short indicator base close to the centre of the crank showed me:

    I am 0.003" TIR out of parallel. Some sources cite 0.002" as acceptable, others (like the manual) cite 0.010". I'm going to call 0.003" "good enough"; it's 'out at the bottom' and who knows what the weight of the gearbox hanging off the mostly unsupported lower half of the bell housing will do, anyway.
    I am 0.016" TIR out of concentricity. The block has been align honed at some point in its life (unsurprising on a block older than me!) which has probably moved the crank centreline up slightly as that's the direction I'm out in - the bell housing is 0.008" too low.

    So I ordered the RobbMc offset dowels from the US, via my boss in Texas (they no longer ship to the UK). He posted them last week before the bank holiday .. so far they have flown from Plano, TX to Chicago. Flown from Chicago to Los Angeles. Flown from Los Angeles to Tokyo(!?) and then they left Tokyo on April 1st.

    They haven't been seen since according to USPS tracking.

    I know.. like a bad joke, right?

    At the weekend I machined a collar with a 0.5015" internal diameter which is a nice slip-fit over the 0.4985" dowels (Draper micrometers so, you know, take accuracy with a grain of salt! Though I checked the 'fit' using a dial indicator mounted to the engine, pointed at the collar on dowel and then 'moved' the collar on the dowel to measure the total deflection which came to ~0.003") and once some new parting inserts arrive (I have a habit of grenading the inserts) I can slice that 0.750" long collar into two 0.375" collars to weld onto the bell housing instead.. unless those offset dowels make a magical reappearance before the weekend!
    Last edited by aaronjb; 07-04-21 at 09:32 AM.
    My DeDion build diary..
    Hon Sec of the Digidash branch of the Unpopular Kit Car Design club

  5. #465
    Join Date
    Jan 2006
    Location
    Chelmsford Essex
    Posts
    1,560
    That's some air miles. I some times am amazed at the route parts take. Sounds like your making nice progress on machining some parts. I do question my Aldu vernior gauge sometimes but it seems to be consistent when compared to some British made gauges. I have a nice dial.gauage I picked up at a boot sale for.peanuts some 20 years ago but it's so.accurate. does 1/10th of a thou !

  6. #466
    Join Date
    Feb 2011
    Location
    Northampton
    Age
    42
    Posts
    4,687
    Likewise I have a mix of very-nearlies (vernier calipers) from branded to Aldi to Chinese no-name and they all seem to be almost as accurate & repeatable as each other.. the difference being that at least the branded ones cleared the grinding dust out of them before assembling, and the Chinese ones feel like you're sliding them through sand! (I should really clean them out..)

    I'd love a "tenths" dial indicator at some point .. my most accurate is my metric Mitutoyo at 0.01mm (or about 4-tenths-of-a-thou).

    The problem I had making the collar(s) though, was that my snap-gauges (for internal bores) have no 'overlap', the <12.7mm gauge fits in the bore but stops at exactly 0.500" so zero clearance, and the next one up (12.7-to-something) doesn't fit in the bore Still, got there in the end by sneaking up on it 0.001" at a time (well, 0.002" as that's 1-thou-per-side on the lathe)


    Hopefully I'll get some time to weld the collars to the bell housing this weekend; I've given up on the offset dowels as they still haven't "reappeared" on the tracking since leaving Tokyo on April 1st..
    My DeDion build diary..
    Hon Sec of the Digidash branch of the Unpopular Kit Car Design club

  7. #467
    Join Date
    Jul 2012
    Location
    NW England
    Posts
    664
    I have a couple of cheap very-nears, not even sure if they have a name on them, a 6" and a 4", they are accurate enough for working in the garage. I must say I find the 4" the most useful, it can get into spaces where the 6" just can't be used. Could probably do with a larger one too for the bigger items too but never got around to it.

  8. #468
    Join Date
    Feb 2011
    Location
    Northampton
    Age
    42
    Posts
    4,687
    I've been meaning to pick up a 4" set - I have a 12" very-nearly and it's been useful about four times.. it's just so huge you can't get it in where you need to (that's what she said)!

  9. #469
    Join Date
    Feb 2011
    Location
    Northampton
    Age
    42
    Posts
    4,687
    I just thought I'd give a comical update..

    So having given up on my offset dowels ever showing up, I drilled the dowel holes out on the bell housing (I had to drill the bolt holes out an extra ~0.3mm too) and got that all dialled in to within about 0.004" TIR both parallel and concentricity. This weekend's job is to weld the collars on to fix the location and that job will be done - I'll post pics when I do that bit.

    Anyway, yesterday (coincidentally the same day I finished dialling the housing in) my boss files a "lost package" form with USPS for my dowels that vanished in Tokyo Haneda airport on 04/01 never to be seen again. Lo and behold, two hours later, my package reappeared and departed Tokyo Haneda airport! Hasn't shown up anywhere else, yet, but oh how we laughed. Sods law, or did filing the complaint make someone look in that big pile of "not sure what to do with these, boss" packages?
    My DeDion build diary..
    Hon Sec of the Digidash branch of the Unpopular Kit Car Design club

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