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Gday brains trust
I drove my HX Sandman home on a permit last night. 60kmph at 2000RPM top gear.
Does this seem right to you guys? It feels like it's revving itself to pieces at 100KMPH
Pete
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Sounds like a 3.55:1 diff.
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Is that what it should be running?
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What tyre rolling diameter do you have, 620 mm or smaller? At 100kph, would you be around 3300 RPM? I would agree with a 3.55:1, the figures stack up. My ute runs a 3.5:1 9", & is in the range of 3250 RPM at 100 kph. My tyre size is around 620 mm. Utility8  Edited by user Friday, 2 July 2010 2:06:39 AM(UTC)
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utility8
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60 at 2000 rpm that has to be a 4.44:1 6 cylinder one tonner diff doesn't it?
In the abscence of any markings on the diff leading you to it's true ratio just mark the tail shaft with something easy to see ie white. Chalk or whiteout will do. Jack up one rear wheel if you don't have an LSD and mark it too. Get someone to turn the lifted wheel two complete revolutions and count how many tiimes your tailshaft turn including partial turns. If you have an LSD lift both rear wheels and turn them only one revolution.
If the tail shaft turns approximately 3.5 turn you would have a 3.55:1 diff.
It won't tell you what your supposed to have under there but it will tell you what you do have.
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3300 rpm at 100kph isn't so bad. Depends what you want. My car is a 3.45 diff and it is about 3300rpm at 100kph with 620mm tyres on the back. I like the takeoff. You can lower the revs, and have slower takeoff. What do you want? If it is old or rare - Cut it! http://www.ehlimo.com.au/ |
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my 1 tonner used to do about 3000rpm at 100 kph.
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If you have 14" rims and 205/70 tyres then at 120kph you do about your diff ratio. Eg I have a 3.08 ratio in the Sandman and at 120kph the tacko reads about 3100rpm. So if your running about the same rolling Dia then I would say you may have a 3.9 ratio?
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Hi,
I would hope with an unique vehicle as a Sandman that you are running the original wheels on it.
Whatever Diff you have I suggest that you consider what purpose you intend using it for as this makes a difference as to which diff you will need.
If you have the standard 6cyl or 253 then 3.08 is a good all round ratio diff
If you have a more powerful engine then the ratio can be stepped up to 2.78.
2.6 can be used if you only use it on flat country roads and do not tow with it.
I have run most diff ratios in most bodys and conditions and I find 3.08 the best compromise of power and performance for any engine size,
If you however only ever drive in traffic and would never take it out of town then perhaps 3.36 would suit you, performance will be up, but so will fuel consumption.
I have a HX ute with a 3.08 diff and it even seems to be reving after modern vehicles.
I have a 2.6 in my HJ Statesman and while it is good most of the time towing heavy lods is a real problem, I want to drop it back to 2.78, but I do have a more powerful Gas engine in this.
Mike
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3.55 isn't exactly common on 308 M21 Sandman, but it was readily available as the "performance" ratio. Standard is 3.36 and is by far and away the most common behind 308 M21.
I'm pretty sure too that 3.55 was the standard ratio behind 253 M20 in HX in an effort to make the choked up ADR27A 253 feel faster!
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It all comes down to what engine/transmission combination the car came with.
Being a commercial vehicle, the 3.55 ratio was standard fare for any 3300 L6 or 4.2 V8 with a manual trans in an HX.
All you've told us is that is an HX Sandman, but is it 3300, 4.2, 5.0, manual, auto ?
Dr Terry
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I guessed 308 M21 or 253 M20 as 90-95% of HX Sandmans I have recorded are in either of these 2 combos.
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Sorry guys, I've been away from the computer for a few days.
This is what the plates state on the van. It's running standard wheels too. It feels like it's working so hard that it has to shorten the life of the engine.
PS: I checked the speed against the GPS and the speedo is spot on.
MOD-HX8WM70
BOD-236624-A
TRIM-1886-18V
PAINT-568-15949
L32 M20 CV7
6/77
1950KG
AHX05152M
SEAT-2
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GV7 is 3:55 ratio. if you do much highway work go for 3:08. Otherwise around town and some highway driving 3:36 will be OK.
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GV7 (not CV7) = 3.55 rear axle ratio.
If you want to reduce the RPM at a given road speed change to 3.36 or 3.08 (or a 5-speed gearbox).
L32/M20, good guess Byron.
Dr Terry
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That explains it.
A 5 speed and a 3.36 sounds like it would make it into a much more drivable car. Is there a 5 speed conversion that won't ruin the integrity of the car that can be converted back to original at a later stage?
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I had a W55 Supra 5spd in a HJ sedan but behind a 6cyl. It was fitted with no body or other mods other than tailshaft. HJ clutch mech is a bit different to HX but it will all still work OK. It had a 3.55:1 diff and was fine. If I were you though I'd just put a 3.08 diff in it. 253 M20 and 3.08 was standard fare in HJ, changed to 3.55 in HX. If your 253 is not all smogged up it'll be fine.
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