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Thread: Mk gearbox and diff rations

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    Mk gearbox and diff rations

    Hi folks
    My mark2 is very long geared.
    T5 box and 3.5 diff
    Ive been looking at diif options and think maybe 4.1 may be an option. Cars for road use with the odd track day.
    2ltr Zetec, twin 45s, lightened flywheel and pulls pretty well.
    Whats the consensus on diff ratios? its lovely on a run as you can trickle along at 70 and its not too noisy but obviously at the expense of a bit of lift.

    T5 gear box
    1st 2.95
    2nd 1.94
    3rd 1.34
    4th 1
    5th 0.8

    Diff 3.5 @ 6000 rpm currently fitted.
    1st Gear = 39.13 mph[FONT="&amp]
    [/FONT]
    2nd Gear = 59.5 mph[FONT="&amp]
    [/FONT]
    3rd Gear = 86.15mph[FONT="&amp]
    [/FONT]
    4th Gear =. 44 mph[FONT="&amp]
    [/FONT]
    5th Gear = 144.3 mph

    @ 3000
    1st Gear = 19.57 mph[FONT="&amp]
    [/FONT]
    2nd Gear = 29.75 mph[FONT="&amp]
    [/FONT]
    3rd Gear = 43.07 mph[FONT="&amp]
    [/FONT]
    4th Gear = 57.72 mph[FONT="&amp]
    [/FONT]
    5th Gear = 72.15 mph


    Diff 4.1 @ 6000rpm
    1st Gear = 33.4 mph[FONT="&amp]
    [/FONT]
    2nd Gear = 50.8 mph[FONT="&amp]
    [/FONT]
    3rd Gear = 73.54 mph[FONT="&amp]
    [/FONT]
    4th Gear = 98.54 mph[FONT="&amp]
    [/FONT]
    5th Gear = 123.18 mph

    @ 3000
    1st Gear = 16.7 mph[FONT="&amp]
    [/FONT]
    2nd Gear = 25.4 mph[FONT="&amp]
    [/FONT]
    3rd Gear = 36.77 mph[FONT="&amp]
    [/FONT]
    4th Gear = 49.27 mph[FONT="&amp]
    [/FONT]
    5th Gear = 61.59 mph


    Diff 4.6 @ 6000rpm
    1st Gear = 29.77 mph[FONT="&amp]
    [/FONT]
    2nd Gear = 45.27 mph[FONT="&amp]
    [/FONT]
    3rd Gear = 65.55 mph[FONT="&amp]
    [/FONT]
    4th Gear = 87.83 mph[FONT="&amp]
    [/FONT]
    5th Gear = 109.79 mph

    @ 3000
    1st Gear = 14.89 mph[FONT="&amp]
    [/FONT]
    2nd Gear = 22.64 mph[FONT="&amp]
    [/FONT]
    3rd Gear = 32.77 mph[FONT="&amp]
    [/FONT]
    4th Gear = 43.92 mph[FONT="&amp]
    [/FONT]
    5th Gear = 54.9 mph
    Last edited by Ally Mac; 22-08-2019 at 18:05.

  2. #2
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    Re: Mk gearbox and diff rations

    id fit a 3.9, easy to come by too being what was fitted to most escorts

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    Re: Mk gearbox and diff rations

    Good luck in finding a 4.1 diff for an Atlas axle as they are very rare unless someone has started reproducing them.

    Is your T5 gearbox out of a 2wd Cosworth? For a road car I would stick with your current gearing as the Zetec engine should have ample torque to pull the tall diff. If you were to use it for competition then lower gearing may be the answer. There's no real solution it's all down to choice, if you had an english axle swapping diffs would be easy assuming you had the various ratios.

    Did you get to the bottom of your rear tail happy problem?
    Last edited by Forest_rallying; 22-08-2019 at 19:06.

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    Re: Mk gearbox and diff rations

    Knew I'd seen a 4.1:1 somewhere. Not sure what the quality is like but I think C Bradley are pretty reputable among the rally boys.


    https://cbradleymotorsport.co.uk/tra...el-pinion.html

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    Re: Mk gearbox and diff rations

    Quote Originally Posted by Forest_rallying View Post
    Good luck in finding a 4.1 diff for an Atlas axle as they are very rare unless someone has started reproducing them.

    Is your T5 gearbox out of a 2wd Cosworth? For a road car I would stick with your current gearing as the Zetec engine should have ample torque to pull the tall diff. If you were to use it for competition then lower gearing may be the answer. There's no real solution it's all down to choice, if you had an english axle swapping diffs would be easy assuming you had the various ratios.

    Did you get to the bottom of your rear tail happy problem?
    I thought I had seen the 4.1 somewhere 3.9 as Graham said is not far away I suppose. Just trying to get my head around all the options. Wont rush into anything just yet. It is nice round the town and ont the open road right enough and as you say there is pretty good torque lower down.


    Its going up on the ramp tomorrow so we will get a good look over the back end.

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    Re: Mk gearbox and diff rations

    Quote Originally Posted by rallyrob View Post
    Knew I'd seen a 4.1:1 somewhere. Not sure what the quality is like but I think C Bradley are pretty reputable among the rally boys.


    https://cbradleymotorsport.co.uk/tra...el-pinion.html

    Thatll be the one

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    Re: Mk gearbox and diff rations

    Quote Originally Posted by rallyrob View Post
    Knew I'd seen a 4.1:1 somewhere. Not sure what the quality is like but I think C Bradley are pretty reputable among the rally boys.


    https://cbradleymotorsport.co.uk/tra...el-pinion.html

    Quote Originally Posted by Ally Mac View Post
    Thatll be the one



    I fancy a 4.3:1 in mine this time round, it's got a 4.6:1 in atm...
    Last edited by rallyrob; 22-08-2019 at 20:43.

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    Re: Mk gearbox and diff rations

    Quote Originally Posted by Ally Mac View Post
    Diff 3.5 @ 6000 rpm currently fitted.
    [/FONT][/COLOR][/B]5th Gear = 144.3 mph

    I was thinking about this part of this. Imo I doubt it would pull that 144mph @6000rpm in top anyway.
    And you'll never get it to do that down the straight at a circuit so the top end part of it is a bit wasted anway.


    It's more of a theoretical speed thing surely?
    Last edited by rallyrob; 23-08-2019 at 08:04.

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    Re: Mk gearbox and diff rations

    Quote Originally Posted by rallyrob View Post
    I was thinking about this part of this. Imo I doubt it would pull that 144mph @6000rpm in top anyway.
    And you'll never get it to do that down the straight at a circuit so the top end part of it is a bit wasted anway.


    It's more of a theoretical speed thing surely?
    Aye, 144 isnt achievable though the others are. I checked a few speeds and rpm on the road. Got the t5 ratios of the net and checked diff ratio. When I put them into the speed cal figures balanced up perfectly. Great wee tool for looking at diff options etc.

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