froggy
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| posted on 12/12/05 at 02:09 PM |
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running a diff backwards?
im just about to order front driveshafts for my 4wd indy and im getting a bit concerned about the front diff .as its a 7" rear unit it will run
backwards and im not sure what effect this will have on the internal workings. the c+p are brand new 3.15 gear sets and will reallly suit my v8. ive
not seen this setup on a car before but hopefully some off road chaps will enlighten me
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Bluemoon
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| posted on 12/12/05 at 02:39 PM |
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Can't you just flip it over, it will run the other way then?
Dan
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stevebubs
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| posted on 12/12/05 at 02:45 PM |
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Why not use a front diff from a 4x4 sierra?
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James
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| posted on 12/12/05 at 02:46 PM |
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quote:
Originally posted by stevebubs
Why not use a front diff from a 4x4 sierra?
I was wondering that!
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"The fight is won or lost far away from witnesses, behind the lines, in the gym and out there on the road, long before I dance under those lights."
- Muhammad Ali
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froggy
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| posted on 12/12/05 at 02:59 PM |
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if youve ever driven a v8 engined car youll know why ! they all have tall diffs in there original applications from 3.08 to 2.8 and dont cruise well
with lower ratios and smaller tyres, if i use the stock 4x4 gears 3.62 the car will be 3000rpm at 70 which is a bit high and the taller final drive
will be a big help for 1/4 mile times as its got plenty of torque to pull it, and no it still runs the same way upside down .
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mark chandler
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| posted on 12/12/05 at 03:00 PM |
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The front diff on a landrover is effectively flipped over to the rear. CWP are ground to run under load one way so you really do want it running the
correct way. However on overrun they are also run the other way without the same applied load.
I believe its more of a noise issue than wear or strength.
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britishtrident
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| posted on 12/12/05 at 03:09 PM |
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With new gears I can't see a problem
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froggy
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| posted on 12/12/05 at 03:11 PM |
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the real world limit for rover v8s is around 280 bhp so the most the diff will see is around 100bhp so i didnt think it would break but the noise
issue is a worry ,perhaps with the c+p being brand new it might be quieter than a worn pinion set being reversed but im sticking with this idea as im
sure its worth over a second over the quarter mile
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steve_gus
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| posted on 12/12/05 at 03:12 PM |
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I can only say what ive seen in 5 years on this board whenever this question comes up. I cant vouch for it.
Apparently if you flip it over and drive it in 'reverse' the helical cut gears will not mesh in the way intended and the diff will have a
short life.
atb
steve
http://www.locostbuilder.co.uk
Just knock off the 's'!
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froggy
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| posted on 12/12/05 at 03:20 PM |
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keep it coming all opinions so far but all welcome still would be good to hear what happens in reality though, it must have been done before!im
thinking that the way the gears have been set will be the same clearance if you run the diff backwards with them being being brand new.
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smart51
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| posted on 12/12/05 at 03:30 PM |
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Sierra diffs have a vent in the top. Turn it over and it will leak.
Use a 4x4 front diff and fit bigger wheels to get your required gearing.
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froggy
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| posted on 12/12/05 at 03:39 PM |
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the diff isnt upside down and 15" is as big as i can go with the body im using . going up to say seventeens wouldnt gain me much in the way of
gearing anyway but it would bugger the handling though
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froggy
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| posted on 12/12/05 at 04:14 PM |
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right , after a bit of searching the current consensus is that it will work if the diff is fitted upside down so that the pinion is pushing on the
"coast" face of the crown wheel but the noise issue is still there, il wait for nsdev to chip in now
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robertwa
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| posted on 12/12/05 at 04:22 PM |
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In my application I'm using a toyota rear axle upside down and spinning backwards as my shaft drive bike engine runs backwards to normal. I read
that running a diff on the coast side of the gears is approx 30% weaker than on the main side (something about the cosine of the angle of the gear). I
figured that the locost is so much lighter than the car the axle came out of that the loading would be lower anyway so I'm not worrying about
it.
The other thing is that the gears will be forced apart a bit as they are contacting on a slope (coast side). This might wear the bearings. Again I am
dismissing this as we are not looking for 200K miles in a locost are we?
Finally, it may vary by the type of diff, but in mine the oil gets flung from the ring gear into a channel to the pinion bearing.
When I flipped and reversed my axle, it didn't look like there was any way of flinging oil up to the pinion bearing (which is now up high and
out of the oil) so I have drilled and tapped for a small electric pump I got from ebay. The pump is used for a diff cooler in racing applications and
also for a turbo pump.
probably an overkill, but I have it anyway.
For your application , since you are not flipping the axle, you may not need to worry about oiling since the pinion bearing is still down low.
FYI, some Jeep Wranglers have a 3.02 front axle. I believe that parts are compatible with Volvo and Ford stuff, so you may be able to find a housing
to suit.
Rob
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theconrodkid
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| posted on 12/12/05 at 04:44 PM |
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as posted earlier land rover diffs are flipped over for the front,you cant run them backwards as they will self distruct in pretty short time,the std
4X4 diff is the shape and size of an oil tanker and is part of the engine sump and cant be fitted for those reasons
who cares who wins
pass the pork pies
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trikerneil
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| posted on 12/12/05 at 04:54 PM |
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My experience FWIW
I originally ran a Sierra open diff upside-down in my trike. Hypoid diffs (I think that's what they're called) are designed so the pinion
pulls itself into mesh against a thrust bearing, if you run it in reverse it pushes off. Th result on my Trike was that transmission noise was
"pushed" down into the bike gearbox to such an extent that I nearly pulled the engine out to investigate. I also found that the gears
would not shift properly. Turning the diff up the right way sorted all my problems. I wouln't recommend it unless the pinion is on the same
centrline as the crownwheel (non hypoid).
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froggy
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| posted on 12/12/05 at 04:57 PM |
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if your talking about the sierra 4x4 front diff then yes it can and has been fitted to various 4wd kits and diffs can be run backwards as thats how
trikes with shaft driven bike engines do it,ive got plenty of opinions now im just waiting to get feedback from anyone who has seen it done
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froggy
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| posted on 12/12/05 at 05:02 PM |
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thanks for that trikerneil but was the diff stilll running backwards when you put it in the right way up?
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trikerneil
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| posted on 12/12/05 at 08:04 PM |
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No the diff was running as Ford intended (rear diff) I reversed the rotation of my bike propshaft. It's just occurred to me I might have saved
myself a lot of work by using a 4x4 front diff - bugger 
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stevebubs
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| posted on 12/12/05 at 09:34 PM |
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quote:
Originally posted by froggy
if youve ever driven a v8 engined car youll know why ! they all have tall diffs in there original applications from 3.08 to 2.8 and dont cruise well
with lower ratios and smaller tyres, if i use the stock 4x4 gears 3.62 the car will be 3000rpm at 70 which is a bit high and the taller final drive
will be a big help for 1/4 mile times as its got plenty of torque to pull it, and no it still runs the same way upside down.
OK...have you considered a freelander diff? This is a much lower ratio (I think) and still IRS all round (again - I think)...
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NS Dev
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| posted on 13/12/05 at 12:30 AM |
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quote:
Originally posted by froggy
right , after a bit of searching the current consensus is that it will work if the diff is fitted upside down so that the pinion is pushing on the
"coast" face of the crown wheel but the noise issue is still there, il wait for nsdev to chip in now
Heh heh!!
Just got in from my grasstrack club agm.........I am chief club scrutineer again......maybe I can ok my own car then!!!
I think the reply from, oh dammit, forgotten the name, but the naked santa chap, is spot on. Hypoid gears, as far as I know, are designed to screw
into mesh with each other, due to the helix angle on the spiral bevel gears. Running backwards I think will trash them, but then I have never done it
personally so that is only based on my engineering assumption plus hearsay!
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JonBowden
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| posted on 13/12/05 at 09:45 AM |
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Sorry, no practical experience here, but clearly if you turn it upside down, the gears will mesh as intended. I can't believe it can be that
hard to block any vents to stop oil leaking and make any other required modifications. You would then be confident in your diff and won't have
people saying nah, it won't last long when they see it.
Jon
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froggy
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| posted on 13/12/05 at 10:04 AM |
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oh TITTYBISCUITS! ive had three axlebuilders say no so far so its a non starter looks like ive got a pair of diffs for sale then
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James
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| posted on 13/12/05 at 11:00 AM |
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quote:
Originally posted by theconrodkid
the std 4X4 diff is the shape and size of an oil tanker and is part of the engine sump and cant be fitted for those reasons
What you on John?!
Loads of Daxs and stuff use it. The front diff is smaller than the rear and it can easily be separated from the sump. Just look at Liam or
EwanSpence's sites.
That's no help for this thread though!
Cheers,
James
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"The fight is won or lost far away from witnesses, behind the lines, in the gym and out there on the road, long before I dance under those lights."
- Muhammad Ali
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trikerneil
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| posted on 13/12/05 at 12:48 PM |
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Naked Santa Chap  ???
I'd better change my avatar before that sticks LOL
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