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Author: Subject: sierra xr4x4 lsd ratios????
oldtimer

posted on 13/2/08 at 08:16 PM Reply With Quote
sierra xr4x4 lsd ratios????

Anybody know where I can get a new or used crownwheel and pinion at 4.44 or 4.7, or even a used complete diff with those ratios???? help!






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JoelP

posted on 13/2/08 at 08:38 PM Reply With Quote
i dont think those ratios were fitted to road cars. You would need a rally supplier i think.
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repper

posted on 13/2/08 at 09:13 PM Reply With Quote
have a look at this from an old post

http://www.locostbuilders.co.uk/photos.php?action=showphoto&photo=Diff%20ratios.jpg






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jacko

posted on 13/2/08 at 09:39 PM Reply With Quote
Hi and welcome to the mad house
for a 3.64/1 try a u2u to Andy w on this forum i think he may have one its a 7.5 diff
Jacko

[Edited on 13/2/08 by jacko]

[Edited on 13/2/08 by jacko]

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oldtimer

posted on 13/2/08 at 09:56 PM Reply With Quote
Ratios...Ratios....Ratios

Thanks for the feedback. The main issue is that I already have a 7inch XR 4X4 lsd but it seems that all the suppliers are out of stock, and I've got to get my ratio up or I'll be using 3 gears and my theoretical and unattainable top speed will be 180mph! I really don't want to contemplate swapping to an alternative diff at this stage.....ideas... help...prayers...
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froggy

posted on 13/2/08 at 10:23 PM Reply With Quote
unles your car has 40" wheels or a twenty speed gearbox with overdrive i cant see why you would need a lower ratio than 3.64 unless ive missed something its normally the other way round with every one after the taller ratios, 3.38 or the holy grail 3.14
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humphfury

posted on 13/2/08 at 10:32 PM Reply With Quote
You could try Raceline, I think they offer a 4.4 and 4.7 CWP.

www.raceline.co.uk

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snapper

posted on 13/2/08 at 11:21 PM Reply With Quote
oldtimer send me your email address and i will send you a very useful excel program that lets you calculate speeds for gear ratios with diff ratios and tyre sizes.
What gearbox are you using? what wheel and tyre are you using? from this information road speed for diff ratio can be calculated.
I have done loads of research on engine revs, gearbox ratios ,diff ratios and tyre sizes.
If you want a 4.4 diff then you need a 4 speed escort ford box or a close ratio (2.3 first gear) Burton/Quaffe type 9 otherwise you will be pulling second gear at about 20mph





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oldtimer

posted on 13/2/08 at 11:55 PM Reply With Quote
Diff ratios

Thanks to all for the super rapid responses. It is a minefield. I would just like to get it right the 1st time if at all possible. My type 9 standard ratio box gives 1st too low and 4th/5th too high. My idea is a type 9 with tall first and short top, coupled to a 4.44 or 4.7 diff (on 205/40/17 tyres) this gives a not too low 1st, good gear spread and a + or - 140 mph top speed (8000rpm) , if I have got all this wrong, (which is possible) please let me know, otherwise whose got a suitable 7" xr4x4 slippery diff??!!.....






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mcerd1

posted on 14/2/08 at 08:26 AM Reply With Quote
quote:
Originally posted by oldtimer My type 9 standard ratio box gives 1st too low and 4th/5th too high. My idea is a type 9 with tall first and short top, coupled to a 4.44 or 4.7 diff (on 205/40/17 tyres) this gives a not too low 1st, good gear spread and a + or - 140 mph top speed (8000rpm)


What engine are you using ?? and where is its peak power likley to be ?

are you using it on the road or track ??

which gearset are you planning on using ?
I'm guessing its something like a BGH E2 with a 2.98 1st /0.87 5th - link: BGH

gearcalc: http://locost7.info/gearcalc.php

I'd suggest using a cheap and chearfull 3.92 7" diff just now
(you can swap the internals with your XR4x4 diff to make a 7" 3.92 LSD - assuming that yours isn't a 2.0 XR4x4 diff, they are 3.92 already)

and only get a 4.44/4.7 crown wheel + pinion for it if you decide you need it once you've driven the car

there is one other option for a standard diff - the scorpio ultima 2.0 8v and 16v cars, they used a 7.5" diff with 100mm CV joints so you'd only need the bigger diff and shorter driveshafts (the rest of your setup should be fine) the 2.0 8v cars had a 4.09 and the 16v had 4.27 - only problem is these car are so ugly that there arn't that many around



I've gone down the 3.92 XR4x4 diff route with my dax, BGH E8 (got a deal on a second hand box), with 245/45 16"

my engine is only a pinto (but not quite a standard one ) I'm guessing at a 7000 - 7500 rev limit to start with (8000 to 9000 with a few upgrades once its on the road) and peak power down about 6000-6500 for now but that just a guess

with this my theoretical top speed is about 163 @ 7500rpm with a 3.92 diff - but in reality it will likley be about 140 @ ~6300rpm, because above that the power will drop off



[Edited on 14/2/08 by mcerd1]

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oldtimer

posted on 14/2/08 at 09:22 AM Reply With Quote
what to do, where to find......

Thanks for your reply. I have picked up a part built locost. Quality of build is v high but no thought went into gearing. Box is standard type 9 with achingly low 1st. BGH box is my chioce but local transmission builders are a bit dispariging about them - how do you find it? Engine is an MR2 20 valve VVTi 1.6 which is 160+ bhp. 95% road use is predicted with the rest occasional track days. Main problem is simply finding the lower (4.44/4.7) ratio diffs - 7" lsd type.






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mcerd1

posted on 14/2/08 at 11:42 AM Reply With Quote
u2u sent
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snapper

posted on 14/2/08 at 01:34 PM Reply With Quote
Oldtimer i think i see your problem
the higher diff ratio is the smaller number not the larger
If you use a 4.7 it will make first shorter effectively giving you an unusable first.
You need the higher 2.8 first gear coupled with a 3.6 diff and even then 5th is quite high giving a theoretical 147mpph top end @6500rpm the 4.7 would give 33 in first 93 in 4th and 114 in 5th using 195 50 15. To go some way to solving the Type 9 wide ratios i have fitted the 3.9 diff with V6 Type 9 box that has a 3.36 first gear and a 6,800 rev limit





I eat to survive
I drink to forget
I breath to pi55 my ex wife off (and now my ex partner)

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oldtimer

posted on 14/2/08 at 04:14 PM Reply With Quote
gears and ratios

Hi and thanks to all. With a BGH type 9 high 1st box and a 3.9 diff are the max speeds in gears not just too high. With my wheels/tyres and 8000rpm max, I would get(max speed ingears) 1st=49mph,2nd=73,3rd=105,4th=143,5th=165mph. These all seem way too high. With a 4.4 diff these become 1st=43mph,2nd=64,3rd=93,4th=127,5th=146mph, and I'm still doing less than 4000rpm in top at 70mph. Does this not make more sense??
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Flat Pack

posted on 14/2/08 at 05:39 PM Reply With Quote
Yeap you're absolutely right. My Striker also has a 20v 4AGE, standard type 9 box and 3.92 diff and gearcalc throws out the same sort of speeds for me (with 195/60/14 tyres).

Ties up with what I've found in practice too, it just feels as though it's geared too long everywhere (except 1st which is too short). I'm planning a 4.7 diff and a long first box at some point.

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oldtimer

posted on 14/2/08 at 06:30 PM Reply With Quote
diffs still

Hooray! somebody agrees with me!! thanks for that - I have many striker bits on my locost, including engine. Raceline and Kamdiffs both recon there are no 4.44 or 4.7 ratios to be had till at least the end of the year, and possibly not even then..............................






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Flat Pack

posted on 15/2/08 at 11:06 AM Reply With Quote
I don't think people realise that we're talking about an engine that'll happily rev to 8000rpm...

It makes a huge difference and if you don't want a theoretical top speed of 170+ you need a shorter diff

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mcerd1

posted on 15/2/08 at 12:52 PM Reply With Quote
quote:
Originally posted by Flat Pack
It makes a huge difference and if you don't want a theoretical top speed of 170+ you need a shorter diff


and a taller 1st to make up for diff

I'll probibly have to change to a 4.44 or 4.7 when I upgrade mine to 16v (~9000rpm limit in theory)

[Edited on 15/2/08 by mcerd1]

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2b_pablo

posted on 15/2/08 at 01:04 PM Reply With Quote
why do people get so concerned over first gear? I cant see it would make any difference bar drag racing?





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if it aint broke... pull it off and upgrade it!

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oldtimer

posted on 15/2/08 at 02:02 PM Reply With Quote
first gear ratio

I think first gear is very important to somebody like me who will do 95% of the time on public roads and nipping into town. I have found a supplier with 4.44 crown wheel and pinion to modify a 7" xr4x4 lsd but those bits alone are £600 excl VAT, Ouch!
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