Outer Limits 4x4 Board

i'm thinking of changing my diff ratios to 4.56 from standard. i currently run 33" tyres which i want to keep (at this stage anyway) as daily tyres, and about to get 35" ET2's for play.

the new diff ratio will be almost spot on for the play tyres, but what effect when running the smaller tyres?



quoted so far
diff gears $1378
diff rebuild kits $290
total (minus fitting) $1668

cheers

Hey, Iv got 4.56's and Im still running on 33's (waiting for them to run down in tread). It revs about 1000rpm harder than factory 4.11 diff ratio's and factory 31inch tyres so its nothing really to worry about but am looking forward to bigger tyres.

I've been running 35's for 5 years and its fine with std gearing, off road its actually better, I have a patrol comp car and the 80 low range is much better. The only thing thats a bit average is winching with my slow mount, but it's about the only time I'm back to 1st even on the 35's.
My wife can drive all over Gembrook on them.
Ive done a couple of club trips with my 36 12.5 Simexs on and the car was fine. The front diff of the 80 isn't very strong and as soon as you go to 4.88 or similar the pinion gets smaller and the tooth engagement to pinion is less so you'll be more likely to break the front crownwheel and pinion.

Joel

all makes sense, thanks. because i plan on running the 33's for daily driving, think i'll be putting off redoing the diff gears to maybe next year. too expensive at this stage.
i could only get prices on 4.56 and 4.88, not on the 4.3 which i would prefer to run.

crankycruiser wrote:i have 4.88's and runs 38's and my speedo is spot on according to the gps

Hey Cranky, so who's C+P did you use, and are they still running ok. My 37's are killing me with the std gearing.
I was worried about the pinion on the 4.88 getting too smal but If you cant break the little sucker then thats good enough for me mate

Also I'm a bit concerned that Marks4WD charges a couple hundred less than Snake, not sure if that more to do with Snake prices being a little on the high side or Mark using an inferior product? Hence my question.

Cheers
LBD

crankycruiser wrote:

dumbdunce wrote:you can get: 3.7:1, 3.9:1, 4.1:1, 4.3:1, 4.56:1, 4.88:1, 5.3:1, 5.7:1 diff gears front and rear for 80 series, there may also be other ratios.

be buggered! didnt realsie there was that many avalible!

but its prolly like u said.. cos they have such good gearing ppl dont generally change em much so u dont hear about them?

i agree, I knew it was more than stock and 4.88, and there is some up in the 6:1 area for the rear only too

I have 4.55 fitted to a petrol auto. They seem pretty good. They were precision from the USA. Haven't broken them yet and I have been reasonably hard on them. I have launched it up a more than afew rock ledges with the swampers and still ok. To be truthful i must admit i am surpised. I honestly would have thought I would have broken it by now. I am not saying I won't but so far so good. I think they were fitted about 8-9 months ago.

mick80 wrote:hey lad ive been doing some ringing round the transfer case gears bbm sell are 40% reduction off the top of my head and they were $1600 +labour to fit them hope this helps
cheers mick

I Wonder how they achieve this ratio ???
considering the size of the transfer case around the low range gear ??

I have a GQ front 4.11 diff (39:9 on crown wheel) and an LC in the rear of my rangie.. Just fitted the other day and soon as I put the centre diff lock in.. well lasted 3 seconds before i took it out.. must have the wrong ratio in the LC diff.. the guy i bought it off obviously thought it was a 4.11 as all 80's have 4.11's

so glad I didn't wreck the transfer

How can I find out what ratio it is before taking the centre out?

cheers

Cameron

Bump

anyone know how to tell what ratio diff I have in an 80 series rear without taking centre out? (I know all 80 series are 4.11 but suspect the one I bought is not)

Cheers

Camo

jack it up, get in in neutral, lock the locker in and turn the shaft,

mark the wheel and the shaft and turn the tailshaft, for each rotation measure how many times the tyre makes a full rotation

How many tyre spins to drive shaft turns should it be for a 4.11?

would that be a way to work out what it is?

I might just do 10 wheel spins and post how many times the shaft spins?? something like that:-)

Camo

Was bored at work so thought I'd do a bit of research into this, as I'm looking at changing my diffs up as well.
Anyway Found me a nifty little proggy that appears to be accurate as long as you have your gear ratio's etc..
Now I did this for my FZJ80 which has a A442F Auto.. so unless you have my setup I'd have to run them again for you, but here's the results.
The gearing for an A442F is 2.95, 1.53, 1.0, .765 with a final 4.11.
The Stock Tyre for an FZJ80 is 275x70R16 which has a circumference of 8.16ft. Using a shift point of 3200rpm speeds for 1st to 4th are:
24 / 47 / 72mph. 60mph is at about 2000rpm in 4th.

If you go to a 315x75R16 (9.06ft) you get:
27 / 52 / 80mph. 60mph is at about 1800rpm in 4th.

To match the stock gearing for that tyre size 4.56 is bang on perfect!

My Creepies are 36.8" or 9.64ft circumference. and with stock 4.11 gears:
29 / 56 / 85mph. 60mph is at 1650ish.. For me If I run 4.88's its bang on std again!

I'll post the graphs to my picasa site if anyone interested i'll link it in tonight.

V8 Rangie wrote:I have a GQ front 4.11 diff (39:9 on crown wheel) and an LC in the rear of my rangie.. Just fitted the other day and soon as I put the centre diff lock in.. well lasted 3 seconds before i took it out.. must have the wrong ratio in the LC diff.. the guy i bought it off obviously thought it was a 4.11 as all 80's have 4.11's

so glad I didn't wreck the transfer

How can I find out what ratio it is before taking the centre out?

cheers

Cameron

Hey isnt 39 / 9 = 4.3? so you have a 4.3 in the front and a 4.1 in the rear.
could that be your issue?

oops sorry my bad

its a 37:9 4.11

so frustrating.. put the 4.11 front centre in the GQ and fitted rear LC diff last sunday and was so sure it was gonna be fine.. oh wells all the hard work done.. drove it with just the rear diff connected and went like a dream :-)

just gotta find the easiest way to figure out the ratio of the LC diff

Cheers guys

Camo

Ah bugger it. Will just take the LC centre out this weekend. Have to in the long run anyways.. Keen as to see what ratio it has!

Camo

LilBlkDuck wrote:

crankycruiser wrote:i have 4.88's and runs 38's and my speedo is spot on according to the gps

Hey Cranky, so who's C+P did you use, and are they still running ok. My 37's are killing me with the std gearing.
I was worried about the pinion on the 4.88 getting too smal but If you cant break the little sucker then thats good enough for me mate

Also I'm a bit concerned that Marks4WD charges a couple hundred less than Snake, not sure if that more to do with Snake prices being a little on the high side or Mark using an inferior product? Hence my question.

Cheers
LBD

Hey ol boy!!

Yer when i first saw the 4.88 pinion i crapped myself.. figured i would break it driving out the shed!!

But it took me 2 years to kill it and it was my own fault.. side stepped the clutch on the limiter in reverse.. lol. mind u done it lots of times b4 so ive been lucky!!

I got mine from J mac in sydney..