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relative strength of 9" vs 8&3/4" diffs

3K views 27 replies 9 participants last post by  WBT56 
#1 ·
I am thinking about changin the standard item in my EL to a 9" arrangement for increased strength (and to take advantage of the superior clutch-pak LSD).

Does anyone know how much stronger the 9" diff is?
 
#2 ·
The 9" is bloody heavy and IS detromental to good handling...Maybe the question should be "Is there agood LSD that can fit the B/W" ????
 
#3 ·
You will also loose about 30HP to turn the 9" so unless you are going to update or feed those neddies some extra "Hay" it will be not worth the effort.
 
#4 ·
Re: relative strength of 9" vs 8&3/4" diffs

you can get your Borg Warner to handle some serious HP as they can put VL diff gears into it as well as ford gears, which gives you a pretty big range of options. Would be cheaper to replace if you break it too.

Get your BW converted to 4 pin LSD. This is enough for a good 1000HP at the fly.

Then watch your tyres melt away. hehehehehe
 
#6 ·
OK. I have a hydratrak lying around in the garage. I have no idea how this type of LSD works, nor any idea of it's robustness. Does anyone out there have any experience with these. They were, I believe, standard equipment on the EL GT and in a lot of HSVs. The standard cone arrangement LSD requires constant rebuilding. We are looking at going to a spool, but do not have time to test this in the car until Mid July, but more likely mid August.

Any thoughts on the Hydratrak appreciated.

cheers,
 
#8 · (Edited)
Re: relative strength of 9" vs 8&3/4" diffs

Excuse my ignorance, what's a hydratrack?
 
#9 ·
Re: relative strength of 9" vs 8&3/4" diffs

Okay, first things first. A 9" does not take 30hp more to turn. This is bollocks. Vl diff gears will fit, but I wouldn't try to run more than 450/500fwhp through them. Anthing more than 650fwhp is going to push the friendship with a BW 75 or 78 series diff, regardless of gears used. At the upper limits, gear strength is not the issue, you are risking outright hemisphere or axle failure. Hydratrack are good in theory, but can be troublesome in use. They use a special coupling to join the axles together instead of the usual cones, and thus require special axles.(and hemisphere, of course) What application is the car to be run in?
 
#10 ·
So your saying that 9" diffs do use up extra "HP" ?

How long have you been around as it has and is a known factor, that it does use extra "HP" to run a 9".

Tell me is there a difference in the Weight of a 9" to a Borg Warner diff ?

Is there more moving parts in a 9" ?

this is only to mention a couple of points.
 
#11 · (Edited)
Fords R Tuff said:
So your saying that 9" diffs do use up extra "HP" ?
How long have you been around as it has and is a known factor, that it does use extra "HP" to run a 9".
In the last three weeks, I have rebuilt five 9" diffs and three BW. How many have you?
Tell me is there a difference in the Weight of a 9" to a Borg Warner diff ?
Comparing 9" LSD 28 spline against BW 4 pinion LSD 28 spline, the 9" is heavier, but as a neutral balanced assembly, once it is spinning at a given speed, it will not take extra power to keep spinning.
Is there more moving parts in a 9" ?
No.
this is only to mention a couple of points.
Does this mean you are backing away from your figure of 30hp?
 
#12 ·
So your saying that Power to Weight ratio there is no difference, when you get you facts then answer and not make foolish comments.

Power to weight ratio is what is and what it's all about.

So that means if you have a Mini with a 351 in it and a 10 ton Truck with the same that they will be equal from a standing start to top speed ?
 
#13 ·
Fords R Tuff said:
So your saying that Power to Weight ratio there is no difference, when you get you facts then answer and not make foolish comments.

Power to weight ratio is what is and what it's all about.

So that means if you have a Mini with a 351 in it and a 10 ton Truck with the same that they will be equal from a standing start to top speed ?
You said nothing about power to weight. If you had said two identical cars, one with a 9" and one with a much lighter BW, were to go heads up the BW equipped, and thus lighter car, would win, then I would have said hell yes.(assuming the BW didn't break)
You in fact said a 9" takes an extra 30hp to turn. This means that the 9" creates a dead loss of an extra 30 hp over a Bw diff, which is BS.
 
#14 ·
Re: relative strength of 9" vs 8&3/4" diffs

Or, lets put it another way. You run your BW equipped mini with one HP and I'll run a 9" equipped mini with 31 HP and I bet I kick your arse.
 
#15 ·
Re: relative strength of 9" vs 8&3/4" diffs

Or, lets put it another way. You run your BW equipped mini with one HP and I'll run a 9" equipped mini with 31 HP, as you have given me a 30HP H/C as that is what a 9" "wastes", and I bet I kick your arse.
 
#16 ·
That's where you loose the extra 30"HP" in weight and power needed to drive the thing.

If not then why wouldn't it be as Quick as the BW diff. ?
as you are saying.

There are a lot more parts in a 9"LSD and heavier than in a BW,

The Diff Carrier alone is nearly as heavy as the BW diff complete.

What do you loose then ? and why ? and why isn;t the 9" as quick as the BW ?
Have you had both on a Dyno ?

I have and in the same car.
 
#17 ·
Fords R Tuff said:
That's where you loose the extra 30"HP" in weight and power needed to drive the thing.
What is the split? 50/50? 50% of 30hp = 15 hp. 15hp = 11.2Kw. So you are saying a 9" dumps out the equivalent of 4.6 fan heaters (give or take)going flat out worth of heat as friction losses MORE than a BW?

If not then why wouldn't it be as Quick as the BW diff. ?
as you are saying.
Define quick. Circuit race, quarter mile, what? Did you compare same ratio/spec diff?

There are a lot more parts in a 9"LSD and heavier than in a BW,
You said moving parts before, but lets see:9" LSD = 39, BW = 28 or 35. Of these, not counting parts that don't have relative movement to each adjacent part INDIVIDUALLY: 9" = 6, BW = 6.

The Diff Carrier alone is nearly as heavy as the BW diff complete.
Not if you compare same/same, as in 302XC BW to 351 XC 9". You can't compare a 31 spline F truck 9" to a 25 spline open XD BW.

What do you loose then ? and why ? and why isn;t the 9" as quick as the BW ?
Have you had both on a Dyno ?
You lose the extra weight you have to cart, and possibly absolute minimal running losses, with the 9". My previous post was clear on this issue. On rough track you may gain lower unsprung weight handling improvements with the BW.

I have and in the same car.
Are you going to try and tell us a diff change gained you 30 rwhp? If so, were the two diffs of the same ratio and spec?
 
#18 ·
go the 9 inch diff in my opinion

they do weigh a bit more than the borg warner shit, but dont forget its "unsprung weight" :s6:

the 9 inch gives you a great selection of gear ratios, and once its in there, just forget about it, cause you wont break it.

and i dont think you would lose any power by using it either, unless some clown did the diff bearings up too tight :bp: hehe

jim :wavey:
 
#19 ·
Yes the two diffs had the same ratio, as I broke three BW diffs including putting a 3] diameter hole in the Hat.
To which I got sick of repairing and the expense.

So in went the 9" out of an XC, oh by the way I modified the Diff housing myself to fit the Coil rear end of the XE.

That is when it went on the dyno, and the results were on the dyno.

I agree with the 9" but they are all breakable if abused the wrong way.
 
#20 ·
Re: relative strength of 9" vs 8&3/4" diffs

Were the BW 4 pin/28 spline? What is the application? What HP?
Was the dyno same operator/same dyno/same ambient conditions/no other changes to car?
 
#21 ·
Everything was the same except I had a shower and changed my clothes, so I don't think that would alter anything.

{You said moving parts before, but lets see:9" LSD = 39, BW = 28 or 35. Of these, not counting parts that don't have relative movement to each adjacent part INDIVIDUALLY: 9" = 6, BW = 6.}

There is a few more parts in the 9" including being heavier and stronger
 
#22 ·
Re: relative strength of 9" vs 8&3/4" diffs

WBT56 said:
Good luck finding falcon hydratrack axles!

Got them too.... I have a complete housing dics to disc fitted with a Hydratrak and 3.23 gears. I changed to a standard LSD arangement when I got a 3.7 ring and pinion. We've made an exceutive decision to stay with the BW at this stage, fitting new 3.9 gears that are allegedly stronger through haveing a different (curved) tooth shape.

The application is a gravel stage EL XR8 rally car generating about 270rwhp, with more to come if we feel so inclined.

I believe I also owe you an apology regarding a discussion we had about the extension housing lengths of T5 gearboxes some time ago. Someone (not me!) had got into the gearbox crates and substituted an AU extension housing into all the EL V8 parts. The AU part is longer, and we discovered this the expensive way after we had had a new input shaft machined......
 
#23 ·
Re: relative strength of 9" vs 8&3/4" diffs

if "fords r tuff" has a broken borg warner, and wbt56 has a working 9", wbt56 will win.
as far as i know, all bw from vn onwards, and i assume ea, are 4 pin. it shouldn't make much of a difference on the road, from bw to 9", except for the easier choice of ratios, unless you have a rotary or 4 cyl, (with no torque).
either way, i dont care, as the 31sp 9" still isnt strong enough for me! i now have a full floating 14bolt chev diff! with 31sp axles, and 10.5" ring gear.
 
#25 ·
Borg Warner diffs are OK for standard or Lightly modified vehicles, but if you are into serious engine mods then the 9" is the answer.

Especially with the amount of Ratio's available for them.
The 9" is the go.
 
#26 ·
Crush,
I used to until I sick of breaking them, but as I said in a thread above that I replaced the BW with a 9" LSD out of an XC and fitted 3.89 Strange diff gears.

Yes I had both setups on the Dyno
 
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