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Gear ratios


Cornish Rattler

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Hi guys

Can anyone shed any clear light on S2a /S3 gear ratios please as I am trying to find out what gearbox would suit my 1971 S2a currently fitted with a Suffix ( F ) gearbox and a 200tdi engine, I have been looking in the Haynes book, and online but they all seem to specify from Suffix ( A ) - ( B ) and from Suffix ( C ) onwards and just wondering if higher Suffix's had higher gearing or not, what do you think :)

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51 minutes ago, missingsid said:

I find it quite confusing as a few months ago I was on their site looking at something else and I came across a table with all the different Suffix's and different landy gearbox's on giving the different ratios of each Suffix / gearbox but as I was looking for something on Defender gearbox's I didn't take much notice of the series Suffix's and ratios and it looks like that's all changed now :mellow:

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I think the main box always had the same ratios, but the transfer box had 3 flavours: series 1/2, which has a 23% lower low box ratio than the later series 2a/3 transfer box. Then there is also the 1 tonne transfer box which is very low in both high and low box. I am not sure how the series and suffix numbers compare.

 

Daan

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They all have the same gearing in 4th; 1:1.  Other than that, there are variations not only between Series model but also suffix letter.  Even reverse ratios vary.

The transfer box high range is the same on the regular transfer box, but the low range was lower on Si and suffix A and B SII.  That is why Series model overdrives will fit all transfer boxes other than 1-ton.  The suffix B gears can be installed in later transfer box to drop low range 17%, but not the suffix A as the intermediate cluster has a smaller internal diameter.  1-ton transfer boxes are similar in architecture but don't have any transferable gears.

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5 hours ago, Snagger said:

They all have the same gearing in 4th; 1:1.  Other than that, there are variations not only between Series model but also suffix letter.  Even reverse ratios vary.

The transfer box high range is the same on the regular transfer box, but the low range was lower on Si and suffix A and B SII.  That is why Series model overdrives will fit all transfer boxes other than 1-ton.  The suffix B gears can be installed in later transfer box to drop low range 17%, but not the suffix A as the intermediate cluster has a smaller internal diameter.  1-ton transfer boxes are similar in architecture but don't have any transferable gears.

Are right I see so really if I was to fit an o/d aswell I would more or less end up with the same gearing as I had with my last one but that was fitted with std diffs, an Ashcroft gearbox and an o/d, I would be happy with that :)

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You'd have the same ratio in 4th and 4th OD as the other vehicle, but the other gears may vary a little.  In practice, you wouldn't notice the difference in 1st-3rd.  The only difference you'd notice would be from vehicle condition and tyre size.

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On ‎2‎/‎25‎/‎2017 at 4:12 PM, Snagger said:

You'd have the same ratio in 4th and 4th OD as the other vehicle, but the other gears may vary a little.  In practice, you wouldn't notice the difference in 1st-3rd.  The only difference you'd notice would be from vehicle condition and tyre size.

Ok I will look round for an o/d to add on aswell, cheer's Snagger ;)

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I think it also comes down to what you want from the vehicle.

 

I'm running 3.54:1 diffs and 8.25 R16 tyres (about 33" tall) with a stock Series 3 88 transfer and gearbox.

On the road it's very good. Will very happily sit and cruise at 60mph. On the level it'll top about 80mph flat out and with a little downhill assistance have trapped 87mph on the GPS.

This is with a non intercooled 200Tdi.

Any taller gearing likely wouldn't offer much benefit and would probably only serve to make it pull less well in top.

 

3rd to 4th there is quite an rpm jump, so you have to hold 3rd a little longer. You really want to get to 40'ish mph. So you can't trundle through 30 limits in 4th anymore.

My gearing spreadsheet says 60mph is about 2500rpm.

The only real issue with this setup is low range. Low 1st crawl speed is now terrible and hinders its ability on technical off road sections.

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11 minutes ago, Chicken Drumstick said:

I think it also comes down to what you want from the vehicle.

 

I'm running 3.54:1 diffs and 8.25 R16 tyres (about 33" tall) with a stock Series 3 88 transfer and gearbox.

On the road it's very good. Will very happily sit and cruise at 60mph. On the level it'll top about 80mph flat out and with a little downhill assistance have trapped 87mph on the GPS.

This is with a non intercooled 200Tdi.

Any taller gearing likely wouldn't offer much benefit and would probably only serve to make it pull less well in top.

 

3rd to 4th there is quite an rpm jump, so you have to hold 3rd a little longer. You really want to get to 40'ish mph. So you can't trundle through 30 limits in 4th anymore.

My gearing spreadsheet says 60mph is about 2500rpm.

The only real issue with this setup is low range. Low 1st crawl speed is now terrible and hinders its ability on technical off road sections.

Yeah with my last 2a I bought another one as a donna car and used the gearbox from that as it looked in better condition than the one originally in mine when my bro opened it up to rebuild for me, and that's when we found out it was an Ashcroft gearbox but the s/n inc the Suffix wasn't present on the gearbox so we never nu what the other gear ratios were so it will be interesting once we get it back on the road :)

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38 minutes ago, Chicken Drumstick said:

In terms of cruising, as someone mentioned above, 4th gear will be the same in any of the gearboxes. 1:1 ratio although the Ashcroft high ratio high range in the transfer box (if fitted) will alter the actual speeds per 1000rpm in all of the gears.

This one is fitted with a std transfer box hence why we have fitted Def diffs and possibly the need for an o/d :)

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As Drumstick says, fitting 3.54 diffs gives a hell of a raise to all gears, including low range, to the tune of about 35%.  I tried it in my 109 and really hated it - it was OK on the motorway as it reduced noise levels (usable top speed increased increased from 60 to 70mph as a result), but acceleration really suffered and town driving needed mid revs in third gear at 30mph instead of a lazy fourth.  I went back to 4.71s as the third gear wheel stripped a few teeth after a few months, though that was probably due to the combination of those diff gears and overdrive.  If you use an overdrive with taller diffs, I urge you to only use the engaged position with fourth gear or low range to avoid damage to the gear box.

I'm now considering 4.1 (upto 4.12, depending on what I can source), as the 4.71s are too low behind a Tdi.

For what it's worth, SII suffix B transfer box low range gears drop the output ratio by 17% compared to later versions, negating the effects of 4.1 diffs in low range and reducing the rise with 3.54s by about half.  They're not cripplingly expensive for new Gen Parts gears and can be fitted without removing the transfer box (just the speedo casing, bottom cover and intermediate cluster shaft).  It gives really low gearing with standard diffs.

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7 minutes ago, Snagger said:

As Drumstick says, fitting 3.54 diffs gives a hell of a raise to all gears, including low range, to the tune of about 35%.  I tried it in my 109 and really hated it - it was OK on the motorway as it reduced noise levels (usable top speed increased increased from 60 to 70mph as a result), but acceleration really suffered and town driving needed mid revs in third gear at 30mph instead of a lazy fourth.  I went back to 4.71s as the third gear wheel stripped a few teeth after a few months, though that was probably due to the combination of those diff gears and overdrive.  If you use an overdrive with taller diffs, I urge you to only use the engaged position with fourth gear or low range to avoid damage to the gear box.

I'm now considering 4.1 (upto 4.12, depending on what I can source), as the 4.71s are too low behind a Tdi.

For what it's worth, SII suffix B transfer box low range gears drop the output ratio by 17% compared to later versions, negating the effects of 4.1 diffs in low range and reducing the rise with 3.54s by about half.  They're not cripplingly expensive for new Gen Parts gears and can be fitted without removing the transfer box (just the speedo casing, bottom cover and intermediate cluster shaft).  It gives really low gearing with standard diffs.

Mmmm something to think about then

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Just out of interests sake. A stock Defender 90 on stock 32" tyres (say a 7.50 or 235/85R16) with the stock 1.4:1 transfer box runs approx 60mph @ 2500rpm.

A stock Discovery 1 on stock 29" tyres with the stock 1.2:1 transfer box also runs approx 60mph @ 2500rpm.

As said above, my setup also does 60mph at 2500rpm. So it's geared pretty similar for cruising. The only real difference is of course only 4 gears. And you can't have a 4th doing 60mph @ 2500rpm and then still be usable at 30mph.

 

OD is great, but IMO prices are crazy on them. Fine if you've already got one, but if you haven't, then unless you happy to be super lucky I'd not bother with one. The Roverdrive offers slightly shorter gearing out of the OD choices, but new they are around £1400!!!!! You'll never recoup that in fuel savings and if you are doing high enough annual mileage to warrant it, then you probably shouldn't be using a Series Land Rover for it ;) lol....

The Ashcroft high ratio high range is probably a much better solution in many ways and a lot cheaper. But still a fair chunk of cash. And of course much more effort and work to fit.

 

The 3.54 diffs are far from ideal, but they are cheap, easy to fit and easy to remove option. If you can combine them with the lower ratio low range, they are probably a good all round bet.

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The diff swap is the cheap option, using the easily available second hand units that exchange hands for £50 or less (each).  HRTC is better because it gives about 32% rather than 35% increase to high range, a more manageable rise, but leaves low range unaffected and also doesn't screw up the speedo like the diff swap does.  It's a pretty modest price, too.  Overdrives are blindingly expensive new, and second hand often have faults or missing parts, but they do give far greater flexibility, being instantly selectable.  Behind a Tdi or V8, any single one of the above still leaves you under geared on the motorway, but the same can be said (to a lesser degree) of Defenders, Discovery's and RRCs.  The only two you can't mix are the HRTC and overdrive, but HRTC and taller diffs would be hopeless for acceleration and would likely break the gear box in the same way as taller diffs and overdrive in third gear did mine.

Depending on your other modifications and how eager you are to maintain your VIN (important if you have reached tax exemption status), then fitting a later transmission with 3.54 may give you better flexibilty and also robustness, with the benefit of much quieter driving.  Ed Parrott did a really good job retaining the existing tunnels and seat base (most retrofit early Defender panels) and the red and yellow levers.

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15 hours ago, Snagger said:

 

For what it's worth, SII suffix B transfer box low range gears drop the output ratio by 17% compared to later versions, negating the effects of 4.1 diffs in low range and reducing the rise with 3.54s by about half.  They're not cripplingly expensive for new Gen Parts gears and can be fitted without removing the transfer box (just the speedo casing, bottom cover and intermediate cluster shaft).  It gives really low gearing with standard diffs.

Hi. Don't suppose you know the part numbers for the bits needed for the low range swap? Really would like to do it on mine. Thanks.

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