GQ rear diff ratio's

Submitted: Saturday, Jan 03, 2004 at 20:29
ThreadID: 9475 Views:4980 Replies:7 FollowUps:5
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I have a diesel with 4.1 : 1 rear diff ratio. I wanted to replace it with a factory locker diff that I picked up. My problem is that I compared the ratio's to check that I had the same.

The diff on my 4wd required 4 and a bit turns on the driveshaft to turn the wheel around completely once. This I thought is how the 4.1 bit works in practice.

I checked the new diff and it only required 2 and a little bit to completely turn the wheel once.

Question, does this make the ratio 2.05 : 1 or 8.2 : 1 ? or am I just plain silly. Then I thought that if I put it in and could get the machine to go, I should be able to do around 250 kph.

Any thoughts.

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Reply By: Voxson (Adelaide) - Saturday, Jan 03, 2004 at 22:26

Saturday, Jan 03, 2004 at 22:26
you are on the right track... it would be 8.2 : 4...
And you would probably need 4 times the hp to reach that speed...___________________________________
Simpson trip 05/04 then turn left at Birdsville to Darwin via Lawn Hill etc
AnswerID: 41669

Reply By: Truckster (Vic) - Saturday, Jan 03, 2004 at 23:50

Saturday, Jan 03, 2004 at 23:50
Look on your compliance plate it will say HG39 HG41 HG43.. thats your diff ratio.
AnswerID: 41676

Follow Up By: fordpatrol - Sunday, Jan 04, 2004 at 11:25

Sunday, Jan 04, 2004 at 11:25
Thanks, but as I said, it is a 4.1 already on the vehicle. I want to know what I have in the factory diff lock.
FollowupID: 304163

Reply By: Nav 80 - Sunday, Jan 04, 2004 at 15:00

Sunday, Jan 04, 2004 at 15:00
If your standard diff is 4.1:1 ie four turns of the drive shaft to one on the axle you cant replace it with a 2.2:1 as it will not match your other diff. Both diffs have to be exactly the same ratio or you will get transmission wind up in 4WD that is the front diff fighting the rear,even different tyre sizes can cause this to some degree.
AnswerID: 41723

Follow Up By: fordpatrol - Sunday, Jan 04, 2004 at 15:44

Sunday, Jan 04, 2004 at 15:44
Yes, thanks for that, I am well aware of what happens when you don't have matching ends. I was totally ignorant of the fact that there was a diff ratio such as this. I am going to have to go to the wreckers and buy a crown & pinion to suit and instal it.
Anybody know what application this ratio would have?
FollowupID: 304183

Reply By: stillthinkinaboutit - Sunday, Jan 04, 2004 at 15:50

Sunday, Jan 04, 2004 at 15:50
As Nav80 mentioned you would also need to change front diff ratio as well.
Also I would not go lower than the 4.1 ratio.
Preference would be the 4.3 or better still the 4.6 if you are running large tyres.

With 2.somethings I doubt you would ever get it to move, you would need to slip the clutch something terrible to get it to take off.
AnswerID: 41727

Follow Up By: fordpatrol - Sunday, Jan 04, 2004 at 16:48

Sunday, Jan 04, 2004 at 16:48
Thanks for all the replies, but everybody seems to have missed my objective. I probably should have spent more time at school.
I have a 4.1 ratio diff in my machine, I have no intention of changing from that. I have obtained a factory diff locker rear axle with this really low (high?) gearing. If I want to use the axle I will have to replace the crown & pinion with a 4.1
What I wanted to know is, what use would this 2.05(?) : 1 ratio be used for. Or I suppose what was it used for before I got hold of it. The last owner did not know.
FollowupID: 304187

Reply By: Truckster (Vic) - Sunday, Jan 04, 2004 at 21:31

Sunday, Jan 04, 2004 at 21:31
So you have a factory GQ Locker correct??

They came out in GQ's with 4.1s standard. They came out of *SOME* Ti Model GQ's, and werent that many of them. They are Vacuum operated, there should be a solinoid on the diff housing, a small black square box thing...

Failing that there would have to be a part # on them, or if there isnt take to Missan and ask them.
AnswerID: 41752

Reply By: Eric Experience. - Monday, Jan 05, 2004 at 23:43

Monday, Jan 05, 2004 at 23:43
If the diff came out of a TI it is 3.9 ratio and you can change the crown wheel and pinion over as long as it is the same housing, some housings have 12 bolts holding them into the housing and some have 9 bolts, as long as you new and old are the same you are ok.
AnswerID: 41891

Reply By: nugget - Monday, Jan 12, 2004 at 19:24

Monday, Jan 12, 2004 at 19:24
I'm assuming that when you turned the driveshaft on the standard diff in the car that both wheels rotated due to it being an LSD. When you turned the yoke on the locking diff were both wheels turning? From your results I 'm guessing only one wheel was turning. This is because it is not an LSD and behaves like an open diff when not locked. The nature of an open diff is allow to different speeds between the axles when cornering up to a ratio of 2:1 to the driveshaft. So if one wheel is completely stopped then all the torque goes to the opposing wheel which will be turning twice as fast as when equal torque is applied to both axles. This being true when you turned the yoke on the locking diff it should only take half the number of turns to rotate the wheel once if you have the same diff ratio (and isn't locked). That is 2.055 turns for a 4.11 diff. Just for interest sake jack one front wheel off the ground, lock that hub and turn the front prop shaft and see how many turns it takes to turn the wheel once. I'll think you will find it takes 2.055.
AnswerID: 42706

Follow Up By: fordpatrol - Monday, Jan 12, 2004 at 20:28

Monday, Jan 12, 2004 at 20:28
Good on you, you got it.
I had a rush of bleep to the brain on the weekend and came up with basically the same result (with the help of a few beers and a mate). I approached it a little bit differently, I sucked on the locker to engage the locked position and uses some vice grips to keep it there. With both wheels turning, it needed around the 4 turns to turn the wheel. I didn't have enough time to play with it longer to establish exactly what the ratio was. I was just happy to know that I didn't have a strange android type diff on my hands.
Thanks, it shows that if you have the patience to think about things long enough, you can make sense of them.
FollowupID: 305061

Follow Up By: nugget - Wednesday, Jan 14, 2004 at 16:03

Wednesday, Jan 14, 2004 at 16:03
Make sure that it is just over 4 turns as their is a 3.9 diff ratio aswell which was in diesel Mavericks. I have seen a factory rear locker in a diesel Maverick.You wouldn't want to fit that instead.
FollowupID: 305245

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