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
Can't you just flip it over, it will run the other way then?
Dan
Why not use a front diff from a 4x4 sierra?
quote:
Originally posted by stevebubs
Why not use a front diff from a 4x4 sierra?
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
.
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.
With new gears I can't see a problem
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
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
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.
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.
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
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
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
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
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).
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
thanks for that trikerneil but was the diff stilll running backwards when you put it in the right way up?
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 
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
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
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.
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
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
Naked Santa Chap 
???
I'd better change my avatar before that sticks LOL
Heh heh!!!
latest update : hillrally cars have used 7" diffs in the front and dmw diffs too .no major probs and not especially noisy, apparently they run them upside down so that the pinion pushes the coast face of the crown wheel. i may have to look at some kind of internal baffle to stop the pinion running dry !
You could call Kevin Mason at Kam Diffs: 01483419779. They make crown wheels and pinions and would surely know.
Colin
The front diff on the Fords I work on everyday are designed to run "backwards so to say. The ring and pinion gear teeth are cut differently then a normal rear diff. They are termed revese rotation R&P's in most catalogs. Hypoid gears are designed to run with the nomal drive load on the convex side of the gear teeth. The diff case is also shaped in such a way that the oil is splashed up to the pinion bearings and then drains down. A rear diff can work running backwards but pinion bearing life is usually very short and starts to get noisey quite quickly. I've seen a few reverse rotation engines raced on the stock car dirt tracks around here. It does work, but its not ideal and requires constant attention.
Running differential gears in the reverse rotation puts forward accelleration on the coast side of the gear tooth. The coast side is the angled side
and transmitts alot of the force toward the sides rather than stright back on the ring gear. I have reversed a chevy corvair transaxle to allow for a
mid engine application. It works but reduces the torque the unit can handle. I have a pic of a diff that was pushed apart from too much torque applied
to the coast side of the gears in reverse rotation, I will try to attach it.. Also running the gears backwards interfears with proper lubrication.
[Edited on 1/15/2006 by wment]
[Edited on 1/15/2006 by wment]
Rescued attachment DiffCracksTop.04.jpeg
il close this one now , the whole thing was my fault as i never thought to check the rotation of the props and although the rear turns clockwise the
front doesnt so thats why ive had to get a front diff etc. bit silly really as i managed to do the bellhousing conversion without any probs