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Thread: Diff refurbish

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  1. #1
    Freshman Member steve00136's Avatar
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    Diff refurbish

    I have just got my car on the road after replacing the diff thrust washers. I was amazed how much play there was in the diff - see video on my blog.....

    https://mgb.tips/2020/01/09/that-diff-is-def-worn/

    Clonk now gone and running well - very pleased.
    1975 MGB Roadster
    Nottingham UK
    blog: mgb.tips

  2. #2
    Great Pumpkin DrEntropy's Avatar
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    Re: Diff refurbish

    This is one of the last things I need to do to mine. The gear lash is excessive. The diff units in these cars are really stout so I've been procrastinating, your post may put some inspiration back into my attitude.
    '64 MGB, '67 Lotus Elan S-3 DHC,'69 Lotus Elan +2
    '78 Alfa Romeo Spider-undergoing surgery: O=\*/=O
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    Great Pumpkin DrEntropy's Avatar
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    Re: Diff refurbish

    Just got some of the bits from Moss yesterday, now I just need to find the room in the garage to do the deed.
    '64 MGB, '67 Lotus Elan S-3 DHC,'69 Lotus Elan +2
    '78 Alfa Romeo Spider-undergoing surgery: O=\*/=O
    '84 300D Turbo-"Diesela"-Now my Daily: Oo|≣|oO
    '02 Toyota Camry- SWMBO's 'new-to-her' Daily. <sigh>
    Chaos & Mayhem PTY, LTD..C.I.O. & Floor Sweepervisor

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    Yoda Randy Forbes's Avatar
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    Re: Diff refurbish

    It has been a long time since I've had an MGB (something in the works right now....) but there were two (2) driveline "fixes" that I would do almost immediately.

    1) was to replace the four (4, 2-flat, 2-conical) thrust washers and the roll pin in the differential.

    2) replace the laygear shaft, needle-rollers, thrust washers & the four (4) synchronizer rings in the xmsn.

    Keep in mind that it's been almost twenty (<20) years since I left my last three (3) MGBs (1-Tourer, and 2-GTs) in my ex-garage...) but the trans tune up was around $100.00 and the parts for the diff were a fraction of that.

    When the laygear shaft wears, the clearance increases between the constant-mesh gears, leading to much more expensive repairs. If the unit had an overdrive fitted, I'd fit new thrust washers and operating piston O-rings.

    The differentials are pretty strong, but with too much slack on the spider gears__and too much horseplay__it is possible to shatter one of the floating spider gears; BTDT. With no other damage, robbing the four (4) spiders from a loose axle and the car (in that case, a Blaze/Navy '73 BGT) was again moving under its own power. It's an easy job, so my recommendation is to get on with it
    http://www.britishcarforum.com/bcf/image.php
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  5. #5
    Great Pumpkin DrEntropy's Avatar
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    Re: Diff refurbish

    I heartily agree, Randy. I've always had at least one MGB and as many as three at a time. All have been the three-synchro boxes, learned to rebuild those back in 1969. Now keep a rebuilt spare in reserve. The diff here now is letting me know it's tired, found a VERY slightly used chunk for sale last week and it arrived Friday. The seller even included a new crush tube! I'll check all in that and swap out the one in the car, along with wheel bearings and seals. Likely would be the right time to put poly bushings in the rear and a rebuilt set of dampers as well. We'll see...

    This is the first time in all those years (and MGB's) that I've had a "spare" chunk. As soon as this old one comes out, it'll get the cups and washers renewed, new crush tube on the pinion, etc. But I don't anticipate needing it in my lifetime, now. The things are really over-built for the car.
    '64 MGB, '67 Lotus Elan S-3 DHC,'69 Lotus Elan +2
    '78 Alfa Romeo Spider-undergoing surgery: O=\*/=O
    '84 300D Turbo-"Diesela"-Now my Daily: Oo|≣|oO
    '02 Toyota Camry- SWMBO's 'new-to-her' Daily. <sigh>
    Chaos & Mayhem PTY, LTD..C.I.O. & Floor Sweepervisor

  6. The Following User Says Thank You to DrEntropy For This Useful Post:

    Randy Forbes (02-23-2020)

  7. #6
    Jedi Knight billspohn's Avatar
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    Re: Diff refurbish

    The Salisbury axle on the late MGBs are clunky and heavy and eat the washers, but at least they are fairly strong even when the clearances are too great.

    The banjo axle weighs 110 lbs. while the Salisbury comes in at 175 lbs., more than 50% heavier and you really don't get much for all that as the early axles stand up well to anything but the most determined Neanderthal behaviour ( ('Hey - let's see how much rubber I can burn...')

    The race cars normally use the early axles (albeit with hybrid ends welded on to eliminate another possible failure mode).

    The issue with the late axles is a combination of washers that wear out and slop in the pinion bearings. Careful set up (as in the previous post) is about as much as you can do to prevent issues.
    Current clutter: 1957 MGA-Jamaican, 1958 MGA Twincam (race car), 1962 MGA Deluxe Coupe, 1971 Jensen Interceptor
    2009 Pontiac Solstice GXP Coupe, 2007 BMW Z4M coupe Recently departed: 1965 Jensen CV-8, 1969 MGC roadster, 1969 Lamborghini Islero S

  8. The Following User Says Thank You to billspohn For This Useful Post:

    Randy Forbes (03-03-2020)

  9. #7
    Great Pumpkin DrEntropy's Avatar
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    Re: Diff refurbish

    Well, as a street car and only occasional driving, this one should last a good while. This car is a "Frankenstein" in that it was put together from other cars well before I got it. Some outfit in Chicago from what I found. It appears to have had a different engine at some point, odd holes in the chassis and other evidence. The banjo diff would have been "period correct" but it isn't an issue for me. Heck, 999 out of 1,000 folks don't even know what make or model it is!
    '64 MGB, '67 Lotus Elan S-3 DHC,'69 Lotus Elan +2
    '78 Alfa Romeo Spider-undergoing surgery: O=\*/=O
    '84 300D Turbo-"Diesela"-Now my Daily: Oo|≣|oO
    '02 Toyota Camry- SWMBO's 'new-to-her' Daily. <sigh>
    Chaos & Mayhem PTY, LTD..C.I.O. & Floor Sweepervisor

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