4.7 R&P for Disco for more Crawl Ratio

[Jay]

Currently running 4.11 R&P on my 1996 disco with GBR axles rear and front,R&F ARB's and 35" ET's. Just finished the set up and tried it out off-roading this weekend the truck needs more crawl.
I m thinking to go with the 4.7 R&P Is it strong enough? Has anyone borken any of them.

[LOCKEE]

Broke both Rover 4.7's and MacNamara Hypoid 4.7's. Tiny Pinions. On a 90 Hybrid 36 Swampers etc.

[Davidh]

How about going for Maxi-Drive's low range reduction gears? I've got the same setup (4.11's/35 ET's) and high range is quite good, but I do agree, lower low range would be better.

Might be a similar price compared to 2 gear sets & fitting, add to that the fact that 4.7's are weaker as LOCKEE said, and your high range will remain the same.

[Jay]

David

How much more crawl increae will I get with MD low range? What gears will you have?
How much is the MD crawler?
What about the 4.75 MD gears?
With 4.7 you will have more high range vs the MD low range crawler?

Lockee:
In what conditions did the 4.7 break roxk climbing , high RPM , gas pedal floored???

[ISUZUROVER]

David

How much more crawl increae will I get with MD low range? What gears will you have?
How much is the MD crawler?
What about the 4.75 MD gears?
With 4.7 you will have more high range vs the MD low range crawler?

Lockee:
In what conditions did the 4.7 break roxk climbing , high RPM , gas pedal floored???

The MD low range gears (calling it a crawler is inaccurate) are 30% lower, so low range is about 4.3:1 instead of 3.32:1. It sells for about $1700+fitting last I asked.

The 4.75 MD gears (made by or for GBR in the US) are stronger than stock series 4.7's.

[Jay]

Ben
Thanks for your reply.
Is the MD low range 1700 U.S.D or AUD ?
What makes the 4.75 MD/GBR R&P stronger than the stock?
With ARB's fitted in won' t the stock 4.7 R&P take the load of 35" since most Rover diff failures is in the beavel gears?

[HSV Rangie]

Rover R&P being centre bevel and not hypoid are very weak.

Lower the diff ratio the smaller the pinion head, the weaker the diff.

Michael.

[Jay]

Ben
Thanks for your reply.
Is the MD low range 1700 U.S.D or AUD ?
What makes the 4.75 MD/GBR R&P stronger than the stock?
With ARB's fitted in won' t the stock 4.7 R&P take the load of 35" since most Rover diff failures is in the beavel gears?

[ISUZUROVER]

Ben
Thanks for your reply.
Is the MD low range 1700 U.S.D or AUD ?
What makes the 4.75 MD/GBR R&P stronger than the stock?
With ARB's fitted in won' t the stock 4.7 R&P take the load of 35" since most Rover diff failures is in the beavel gears?

AUD

The standard R&P are 10 pinion teeth and 47 crownwheel teeth (47/10=4.7). The 4.75 is 38/8. Most 4.7:1 failures are on the ring so this gives a stronger ring gear as the teeth are thicker. It probably also helps that they are a stronger/better material than the series 4.7's.

Like Michael said though, spiral bevel diffs are an old design and quite weak.

[daddylonglegs]

The Rover 4.7:1 diffs are weak because apart from being spiral bevel instead of hypoid bevel the have 10 small teeth on the pinion and 47 small teeth on the ring gear. The MD/ GBR 4.75's have 8 thick teeth on the pinion and 38 thick teeth on the ring gear. Thick teeth can have a good depth of case hardening to resist wear as well as a thick ductile core for shock resistance.
Bill.

[Jay]

AUD

The standard R&P are 10 pinion teeth and 47 crownwheel teeth (47/10=4.7). The 4.75 is 38/8. Most 4.7:1 failures are on the ring so this gives a stronger ring gear as the teeth are thicker. It probably also helps that they are a stronger/better material than the series 4.7's.

Like Michael said though, spiral bevel diffs are an old design and quite weak.[/quote]

Ben

Thanks for your reply. Has anyone broken an MD/GBR 4.75 R&P? Do u know anyone who has fitted them on 35+ tires Disco?
What makes the hupoid deisgn much stronger(is it the reverse cut of the spiral bevel diffs)?

[ISUZUROVER]

There are a number of people on the rover section of www.pirate4x4.com that have broken the 4.75:1 ring and pinions. Do a search over there.

The hypoid diff is a lot stronger since the pinion is not pointing towards the centre of the ring gear so more teeth are in contact with each other. Again, look it up on www.howstuffworks.com or a similar site. Salisbury diffs are a hypoid design, as are just about all other diffs on the market.

[will_warne]

The other thing to watch with 4.75 r&ps is they tend to shear crown wheel bolts. I know of a few guys who've done that, the last one who did wrecked his ARB 'locker.

[Jay]

The other thing to watch with 4.75 r&ps is they tend to shear crown wheel bolts. I know of a few guys who've done that, the last one who did wrecked his ARB 'locker.

Will
What makes the 4.75 shear down the crown wheel dolts more than the 4.11?
What are guys in the UK runnin on 35" as CR&P

JAY

[daddylonglegs]

I may be wrong but think that there may be 2 different 4.75 gear sets. one is designed to go on 3.54 carriers.and the other for 4.7 carriers. If you mismatch them you may need a spacer ring and longer crownwheel bolts which will increase the likelihood of shearing them.
Bill.

[J Top]

Also I think Rover state that their crownwheel bolts are one use only and should be renewed,not reused.
J Top

[HSV Rangie]

Also I think Rover state that their crownwheel bolts are one use only and should be renewed,not reused.
J Top

All High tensile bolts are one use only.

Michael.

[aliread]

The other thing to watch with 4.75 r&ps is they tend to shear crown wheel bolts. I know of a few guys who've done that, the last one who did wrecked his ARB 'locker.

Will
What makes the 4.75 shear down the crown wheel dolts more than the 4.11?
What are guys in the UK runnin on 35" as CR&P

JAY

Hi Will that would be me that broke the bolts on the crown wheel. Did not too much to the ARB, but problem was not fitted long enough bolts. Fitted longer and seems to have sorted it

[aliread]

Currently running 4.11 R&P on my 1996 disco with GBR axles rear and front,R&F ARB's and 35" ET's. Just finished the set up and tried it out off-roading this weekend the truck needs more crawl.
I m thinking to go with the 4.7 R&P Is it strong enough? Has anyone borken any of them.

Since fitting the 35" Simex tyres I have found tha same problem and the gearing to be too high This means that I am going though clutches in about 2000 miles. It also made it fun to drive off road as the 1 st gear in low was still a bit too high. I needed to change my gearing to cope with this. So I changed from the 90 (3.5) gearing to the Series (4.7) gear ratios for the Diffs. This is because the extra gear the simex have given me is 28% , work on the fact that the original tyres supplied with the 90 from the factory were 205's. If you fit 4.7 ring and pinions it will take me down by 30%, so almost about right to the factory settings But the only problem is that the ring and pinions for a series diff are as strong as toffee. The only way around this is to get the Kam ring and pinions, which are stronger. They are mainly used for the racing boys in comp safari. As you can see from the pictures they are allot stronger and thicker than the original 3.5 These placed in the Diff along with the ARB and Maxi Drive shafts, should in my mine give me the strongest Land Rover axle I can get.
But i have broken the bolts but put this down to the wrong bolts . Still rate them as bloody strong though
On the left 4.75 Kam ring and on the right standard 3.5 Ring, as you can see they are thicker





This is a picture of them made up into the diff. As you can see more mean looking than the original

[Jay]

Aliread,

Are you still running the 4.7 Diffs from Kam?
Do u have a V8 under the hood on your D 90?
Are you running MD axles and CV's?

Thanks
JAY

[aliread]

Aliread,

Are you still running the 4.7 Diffs from Kam?
Do u have a V8 under the hood on your D 90?
Are you running MD axles and CV's?

Thanks
JAY

Oh yeah
They are the muts. I am running a 200 TDi
But my brother has a set of them in his 4.2V8 Defender 90
I am running MD rear with Kam front (24 spline) and Aue2522 CV's with GKN overload protectors, so no need to worry about the CV's as they take care of that
Thsi is my front set up

[tony cordell]

Currently running 4.11 R&P on my 1996 disco with GBR axles rear and front,R&F ARB's and 35" ET's. Just finished the set up and tried it out off-roading this weekend the truck needs more crawl.
I m thinking to go with the 4.7 R&P Is it strong enough? Has anyone borken any of them.

Since fitting the 35" Simex tyres I have found tha same problem and the gearing to be too high This means that I am going though clutches in about 2000 miles. It also made it fun to drive off road as the 1 st gear in low was still a bit too high. I needed to change my gearing to cope with this. So I changed from the 90 (3.5) gearing to the Series (4.7) gear ratios for the Diffs. This is because the extra gear the simex have given me is 28% , work on the fact that the original tyres supplied with the 90 from the factory were 205's. If you fit 4.7 ring and pinions it will take me down by 30%, so almost about right to the factory settings But the only problem is that the ring and pinions for a series diff are as strong as toffee. The only way around this is to get the Kam ring and pinions, which are stronger. They are mainly used for the racing boys in comp safari. As you can see from the pictures they are allot stronger and thicker than the original 3.5 These placed in the Diff along with the ARB and Maxi Drive shafts, should in my mine give me the strongest Land Rover axle I can get.
But i have broken the bolts but put this down to the wrong bolts . Still rate them as bloody strong though
On the left 4.75 Kam ring and on the right standard 3.5 Ring, as you can see they are thicker


Ali
The thickness is only due to the pinion being so much smaller I would have thought.
how many teeth are on the KAM pinion?

[aliread]

Ali
The thickness is only due to the pinion being so much smaller I would have thought.
how many teeth are on the KAM pinion?

The pinion is still big and chunky
Can't remeber how many teeth there are on the pinion, But the they are bigger teeth , but the ring and pinion are rated for up to 500Bhp
Which is more than enough for a TDi
here is pic of old and new
The Kam ones are the ones on the right

[DiscoDino]

Why go round in circles? Toy set-up rules. SIMPLE and EASY (and actually, cost effective!), choose from more than a couple of ratios, lots of lockers/lokkas, 30 spline axles, and longfields...

"I've seen the light"

(P.S., 500hp rating on 28x7.5 or 44x15.5 tires? difference...)

[daddylonglegs]

Any manufacturer that gives a 500bhp rating on stuff like this is guilty of talking BS
Horsepower ratings are meaningless, its torque , shockloading and fatigue that kills transmission components. The KAM and GBR ring and pinions are an improvement over stock but they are a long way from being indestructable. they are still spiral bevel and therefore nowhere near as strong as a differential with an almost 9 inch diameter ring gear should be.
Bill.

[aliread]

Any manufacturer that gives a 500bhp rating on stuff like this is guilty of talking BS
Horsepower ratings are meaningless, its torque , shockloading and fatigue that kills transmission components. The KAM and GBR ring and pinions are an improvement over stock but they are a long way from being indestructable. they are still spiral bevel and therefore nowhere near as strong as a differential with an almost 9 inch diameter ring gear should be.
Bill.

Yeah but no , but yeah, but
, my truck is a TDi there for only 110BHp on a good day so taking BS into account i thought (as they have proved ) to be fine
After all i do have a name for being a ruff arse and most of the stuff on my truck does not last long. And the ring and pinions have. And to my knowledge they are the strongest you can get in the Uk at the moment (that will fit straight into a Land Rover Diff.)

[tony cordell]

Ali who built them up for you?
did you do it yourself
as I have never re built a diff and don't fancy practiceing on my own ones

[aliread]

Ali who built them up for you?
did you do it yourself
as I have never re built a diff and don't fancy practiceing on my own ones

Frogs Island Built them up for me
Tonk built up my brothers set and his own set

[will_warne]

I think the one to watch if your worried about strength is Jules'. With the power he's got and the way he drives, any strength issues will soon show themselves

[aliread]

I think the one to watch if your worried about strength is Jules'. With the power he's got and the way he drives, any strength issues will soon show themselves

Yeah too true
Well of to a comp with him and Mark tomorrow . So will let you know