different diff ratios

Submitted: Sunday, May 08, 2005 at 10:00
ThreadID: 22764 Views:1359 Replies:7 FollowUps:9
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Can a 4wd operate with different ratios in the frony and rear diffs? I say no however my stubborn son wants to use his forerunner with the odd diffs.My major concern is he is not the one paying for any damage.

Terry
The scrub is something terrible. Oh, what a damnable, treacherous, God forsaken country it is to be sure. I believe it would sicken the Devil himself.

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Reply By: Member - JohnR (Vic) - Sunday, May 08, 2005 at 10:24

Sunday, May 08, 2005 at 10:24
Terry, if he had a diff between the front and rear axles it would be a means of balancing torque. Having a locked front/rear connections in the simplest transfer cases like a Hilux a recipe for trouble. When engaged as 4wd on a hard surface, instant wind up of transmission, diffs front and rear as soon as you progress in any gear. Immediate wear of tyres and gear trains, lower available power as one diff either tries to overtake the other or pull the chassis apart.

Is he intending to have the numerically higher one at the front or the rear? I'd be terrified too......
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Reply By: Barnray - Sunday, May 08, 2005 at 10:25

Sunday, May 08, 2005 at 10:25
If he wants to bust his G,box,diffs drive shafts etc tell him to go ahead. Windup is bad enough without adding to the problem. Barnray
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Follow Up By: Terryfied - Sunday, May 08, 2005 at 21:41

Sunday, May 08, 2005 at 21:41
Sometimes I think he is the problem!

Terry
The scrub is something terrible. Oh, what a damnable, treacherous, God forsaken country it is to be sure. I believe it would sicken the Devil himself.

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Reply By: GaryInOz (Vic) - Sunday, May 08, 2005 at 10:51

Sunday, May 08, 2005 at 10:51
Up to a couple of percent difference is OK. As an example the old 1980-1983 Subarus had a 3.88 front and a 3.9 rear. You can realistically get this effect by having a heavily loaded vehicle in 4WD anyway.

As for running (say) 3.9's and 4.1's (5%) that might be a bit of an ask on hard surfaces but OK on loose surfaces. Any more of a difference than that is asking for some peculiar and potentially dangerous handling

As advised above, make sure the front is numerically lower than the rear (rotates more per driveshaft rpm =>forced understeer), otherwise it would be a handful, and very dangerous particularly down slopes.
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Reply By: Outnabout David (SA) - Sunday, May 08, 2005 at 12:29

Sunday, May 08, 2005 at 12:29
In a word "BANG"
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Follow Up By: Terryfied - Sunday, May 08, 2005 at 21:43

Sunday, May 08, 2005 at 21:43
My thoughts exactly.

Terry
The scrub is something terrible. Oh, what a damnable, treacherous, God forsaken country it is to be sure. I believe it would sicken the Devil himself.

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Reply By: Savvas - Sunday, May 08, 2005 at 13:07

Sunday, May 08, 2005 at 13:07
Hi Terry,

In a part time 4WD, it's a very bad idea.

Tell him he can go ahead with it, but he should also get a spare drivetrain before he starts. It won't be long before he's swapping out broken bits.

What is it he wants to achieve by doing this anyway? I can't possibly see why he would want one set of wheels spinning at a different rate to the other.
AnswerID: 110287

Follow Up By: Terryfied - Sunday, May 08, 2005 at 21:39

Sunday, May 08, 2005 at 21:39
Savvas,he is just too lazy to put the other diff in .Maybe it has to do with the fact he/I do not want to remove the cv joints,the last time I did cvs was on a 1974 Austin 1800 about that many years ago.

Terry
The scrub is something terrible. Oh, what a damnable, treacherous, God forsaken country it is to be sure. I believe it would sicken the Devil himself.

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Follow Up By: Truckster (Vic) - Sunday, May 08, 2005 at 22:21

Sunday, May 08, 2005 at 22:21
Changing a Blown CV is the issue? it would be easier to change a CV than a diff.... by a long shot
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Reply By: Member - Jiarna (SA) - Sunday, May 08, 2005 at 15:39

Sunday, May 08, 2005 at 15:39
VERY briefly LOL
Those who say something cannot be done should not interrupt the person doing it.

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Reply By: Member - Davoe (WA) - Sunday, May 08, 2005 at 15:44

Sunday, May 08, 2005 at 15:44
This is already done with the transfercase having a different ratio front to rear whichis the cause of windup on hard ground. HOWEVER it is minimal compared to different ratio diffs (I think about 48:52) . would call it a stupid idea but i had a mate who turned the diff over in his litestout to jack up the back end and ended up with 4 revesr gears and one forward. Different ratios front to back is just as smart
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Follow Up By: Wayne (NSW) - Sunday, May 08, 2005 at 15:53

Sunday, May 08, 2005 at 15:53
Davoe,

The gear box is where the forward and reverse come from not the diff. It would not matter if it was right way up or not it would still turn the wheels in a forward direction if a forward gear was selected.

Wayne
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Follow Up By: Member - Davoe (WA) - Sunday, May 08, 2005 at 15:59

Sunday, May 08, 2005 at 15:59
Nu wrong. That is the logic my mate used, My other 2 mates (the smart ones) told him what would go wrong. I was there at the test firing and can assure you an upside down diff runs backwards
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Follow Up By: Member - John (Vic) - Sunday, May 08, 2005 at 16:06

Sunday, May 08, 2005 at 16:06
Boy this will turn into an interesting thread. LOL
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Follow Up By: Wayne (NSW) - Sunday, May 08, 2005 at 16:12

Sunday, May 08, 2005 at 16:12
Davoe,

You are right. I used a pencil and rotated it to wards me, as I turned it over it was rotating away from me.

Wayne
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Follow Up By: Member - Davoe (WA) - Sunday, May 08, 2005 at 16:16

Sunday, May 08, 2005 at 16:16
and if yo imaging another pencil running into it as the tailshaft it will continue to run the same direction as the other pencil turns
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