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Thread: Gear Ratios

Forum to discuss Austin Healey Sports Cars

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    Jedi Hopeful Griz's Avatar
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    Gear Ratios

    I had heard this was the case, but now that I've nearly completed my BJ7 restoration and have been driving it for a few weeks, I see that there is really not much difference between 1st and 2nd gear. With all the engine torque available I find that starting in 2nd gear is no problem at all and I find myself doing so frequently. I'm curious, how many of you typically start out in 2nd? The only down-side I can see is maybe a little extra wear on the clutch disk.

    Griz

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    Darth Vader Michael Oritt's Avatar
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    Re: Gear Ratios

    Lugging an engine--as in applying a big load at too low rpm's in any gear--puts undue strain upon big end bearings, and I can't help but think that starting off the line in 2nd induces a similar load on the engine.

    To me part of the joy of driving cars such as ours is working through the gears and if anything perhaps I am guilty of using the shifter more often than I have to, looking to stay in the power band.

    Best--Michael Oritt
    1954 Austin-Healey 100 Lemans
    1958 Elva Courier (FOR SALE)
    1959 Elva MK IV Sports Racer
    1961 Ginetta G4

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    Yoda
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    Re: Gear Ratios

    I always start in 1st from a full stop; this is one--of several, IMO--benefits of a 3.54 rear-end: it makes both 1st and 2nd more usable. I will start in 2nd if I'm at least rolling a bit, since it has a synchro. I did start in 2nd from a stop at least occasionally before I put the taller rear-end in. When I recently replaced the clutch disk it had a broken spring, and I half suspect this behavior may have caused it.

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    Darth Vader Michael Oritt's Avatar
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    Re: Gear Ratios

    I too have the 3.5 diff in my 100 (as well as a Smitty's five-speed conversion) which does make first a more useful and less noisy/jerky experience, but I still believe that first should be used from a stop no matter what box you have. Since first is non-synchro'd there is often a slight gear crunch when shifting into it from neutral and if this bothers you simply touch the very "edge" of second gear before pushing the stick into first (or even reverse)--the noise will be no more.

    Best--Michael Oritt
    1954 Austin-Healey 100 Lemans
    1958 Elva Courier (FOR SALE)
    1959 Elva MK IV Sports Racer
    1961 Ginetta G4

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    Jedi Hopeful Griz's Avatar
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    Re: Gear Ratios

    Too lazy right now to go get my service manual to look it up, but if 3.54 diff is the "taller" rear, what is the standard ratio (which I am positive I have)?

    Griz

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    Darth Vader Michael Oritt's Avatar
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    Re: Gear Ratios

    3.9:1

    Best--Michael Oritt
    1954 Austin-Healey 100 Lemans
    1958 Elva Courier (FOR SALE)
    1959 Elva MK IV Sports Racer
    1961 Ginetta G4

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    Yoda
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    Re: Gear Ratios

    For 6-cyl cars with 22% OD, 3.91; for a 100 I believe it was 4.10 (with a 28% OD). For 6-cyl cars w/o OD the std. diff was 3.54.

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    Re: Gear Ratios

    Unless I'm on an uphill grade, I always start in 2nd. With the 3.91 rear end there's no lugging or slipping of the clutch involved.

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    Re: Gear Ratios

    Quote Originally Posted by Bob_Spidell View Post
    I always start in 1st from a full stop; this is one--of several, IMO--benefits of a 3.54 rear-end: it makes both 1st and 2nd more usable. I will start in 2nd if I'm at least rolling a bit, since it has a synchro. I did start in 2nd from a stop at least occasionally before I put the taller rear-end in. When I recently replaced the clutch disk it had a broken spring, and I half suspect this behavior may have caused it.
    Dido -

    Install the 3.54:1 gears and really enjoy the big Healey 6-cylinder.
    Dougie
    '65 BJ8 3000 MKIII GN.29
    '57 100-SIX MM Vintage Racer GN.1 #414
    Team Healey PDX

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    Darth Vader John Turney's Avatar
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    Re: Gear Ratios

    I have the the 4.10 on my BN4 with OD. I always start in 2nd unless I'm pulling into the garage or caught in stop&go traffic. Even then it may not be low enough.
    John, BN4

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    Jedi Knight DerekJ's Avatar
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    Re: Gear Ratios

    In terms of ratio there is in fact a big difference between 1st and 2nd gear. See the attached chart.
    Attached Images Attached Images

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    Re: Gear Ratios

    Will the 3:54 gear set in my 65 BJ8 with OD make that much of a difference? $800
    on sale at Moss now. Not exactly chump change. How would it pull when cruising
    in OD, especially on a hill?

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    Yoda
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    Re: Gear Ratios

    Quote Originally Posted by dancrim View Post
    Will the 3:54 gear set in my 65 BJ8 with OD make that much of a difference? $800 on sale at Moss now.
    Not exactly chump change.
    Depends on how much and what kind of driving you do. I put a lot of miles on my BJ8--around 5K/year--and, while I prefer the backroads and twisties like most of us, I often have to drive many miles on highways and freeways to get to them. The 11% reduction in engine RPM wrought by the taller rearend significantly reduces vibration and engine noise around 70MPH, which you have to at least do to avoid being steamrolled by soccer moms in huge SUVs and douche-bros in their jacked-up city cruiser trucks. Although your 0-60 times will be increased a shade--and you'll need to get a ratio adapter or new gears in your speedometer--a well-tuned Big Healey engine has plenty of torque for the extra load.

    A stock 3.91 diff with a taller OD--a 28% should be a drop-in--might be a good solution as well, and I've heard from at least one knowledgeable aficionado that a 3.54 rearend AND the taller OD makes the best highway cruiser of all. BTW, the 'original' 3.54 rearend was initially manufactured and sold by Mike Lempert--of custom steering wheel fame--for $200. There will also be shop setup fees, unless you're comfortable installing rearends.

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    Darth Vader Michael Oritt's Avatar
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    Re: Gear Ratios

    Dancrim--

    You're not going to save $800.00 as a result of lower fuel consumption but it sure will make a difference in the way your car feels at cruising speeds. Before installing the 3.5 I always felt I was "pushing against a wall" when travelling at 65-70+ mph. Now I am turning about 75 at a comfortable 3000 rpm's and because the Healey's power band is pretty broad I am usually able to make a pass without going down into 4th.
    Last edited by Michael Oritt; 10-27-2017 at 05:14 PM.

    Best--Michael Oritt
    1954 Austin-Healey 100 Lemans
    1958 Elva Courier (FOR SALE)
    1959 Elva MK IV Sports Racer
    1961 Ginetta G4

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    Re: Gear Ratios

    I bought my 3.5 pinion and ring gear from SC Parts in the UK for considerably less. I had it professionally installed in a differential provided by a fellow Healey club member. I think that cost was just over $250. Subsequently my fellow club members helped install the upgraded differential in my '60 BN7. It is absolutely silent. By the way, this car has a Smitty Toyota conversion. Likely it wasn't the best choice, not a Supra, etc., and likely from a truck as it was turning about 3000 RPM at 60 mph before the conversion. Changing the differential substantially reduced my RPMs in all gears, most noticeably in 5th.
    Owner of a 1960 BN7 with Toyota 5 speed and a '92 Porsche 968 coupe. Former owner '62 Jaguar MK2, MG-TF brought back from military service in Italy 1958, '61 Healey BT7, pre-A Porsche 356, and a Porsche 944.

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    Darth Vader steveg's Avatar
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    Re: Gear Ratios

    I have the Supra 28% OD 5th with the original Lempert 3.54 diff. 3000 rpms is pushing 80mph. A friend has the 3.54 with 28% orig OD - same.

    I also have the DWR 8, 278 degree cam. The Healey has plenty of torque to support this setup. Unequivocally recommended.
    Steve Gerow
    Altadena, CA, USA
    Maker of most complete Big Healey rear disc kit
    Check out my galleries:
    http://www.pbase.com/stevegerow

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    Re: Gear Ratios

    Thanks guys. I guess I'll break down and go for it. Retired now and the car is getting a lot more use. Thanks again.

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    Re: Gear Ratios

    I'm having a 3.54 ring and pinion installed in my AH 3000 BJ7 in the next few weeks. The mechanic doing the work will also check and replace bearings etc. if necessary. With essentially new differential components, what type gear oil is best? I read some about those running Redline gear oil (e.g. 75W x 90, GL-5) so is this suitable for diffs specifying GL-4? Thanks for the clarification. GONZO

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    Darth Vader Michael Oritt's Avatar
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    Re: Gear Ratios

    Gonzo--

    Differentials use a GL5 oil and transmissions with yellow metal such as ours use a GL4.
    I use Amzoil Severe Gear 75-90 in the diff and Redline MT90 in the transmission.
    Opinions will vary but do NOT use any GL5 product in your transmission as it will attack the synchros. Some diff oils claim a Gl4/5 rating but I am skeptical.

    Best--Michael Oritt
    1954 Austin-Healey 100 Lemans
    1958 Elva Courier (FOR SALE)
    1959 Elva MK IV Sports Racer
    1961 Ginetta G4

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    Yoda HealeyRick's Avatar
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    Re: Gear Ratios

    Don't forget that like a new engine, your new differential gears need break-in as well. Here's some guidelines: https://www.marlincrawler.com/tech/d...re-information I agree with Michael, you don't really need, nor want, anything different than GL4 in the rear. Your speedo will now be out of calibration. You can either send it off to a place like Nisonger or use this GPS based device I use: https://www.classicautoinnovations.com/classic


    Rick

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