Raising the compression?

gtirx2

gtirx2

Active Member
Odin said:
What I was really trying to get at was that I wasn't sure if both diffs where exactly the same, Being that the centre diffs job is to split the drive 50/50 safely, But i have no idea how the rear splits the drive, Most of the time it would be 50/50 but just how it controls the split under different loads goes straight over my head.



Rob
Click to expand...
The diffs are sealed units.
I get what you are trying to say and tbh i would think it would all come down to the condtion of the fluid in the diff as to how much torque it could transfer?
Another intresting thing i read is something about an air bubble inside a viscous diff,i would asume that this would also have something to do with how hard it would lock and how soon?


Viscous
The viscous differential also has interleaved plates, and in fact works because of the viscosity (internal friction) of the silicone fluid that fills the gaps between the plates. The plates therefore do not actually touch one another. The percentage of torque transfer varies with the difference in speed between the two wheels, partly as a result of the plate design and spacing, and partly because of a physical property of silicone fluid that it experiences virtually no change in viscosity when heated. If one wheel is rotating only a little faster than the other, only a little torque transfer occurs, when there is a big difference between the speeds of the two wheels, the viscous differential will transfer up to 95 percent of the torque to the wheel with traction. Because of the difficulties in handling the silicone fluid, servicing a viscous differential can be accomplished only with special equipment. The silicone fluid is under pressure, and there is an air bubble of known (and controlled) volume included in the differential casing. Any deviation from the correct amount of pressure or air bubble volume can radically change the characteristics of the differential.
 
O

Odin

Guest
gtirx2 said:
Any deviation from the correct amount of pressure or air bubble volume can radically change the characteristics of the differential.
Click to expand...

Well you learn something new everyday :shock: 8) .

I knew how the fluid worked but I had no idea about their being a bubble :shock: .


Rob
 
gtirx2

gtirx2

Active Member
LOL you have even got me thinking now:doh: :lol: ,do viscous diffs have a power rating that they can handle depending on fluid thickness and air bubble size?
For instance if the center diff in the R was only rated to say 300ft/lb torque and you was running 400++ft/lb would the torque split still be 50/50? as where you have to much power for the diff to cope with would it not just spin the power away at the front where the center diff is not capable of handling the extra torque making the torque split more like 70/30?
Thats if you understand what i mean as i think i could be confusing myself here:lol: :doh:
 
Last edited:
warringtonjack

warringtonjack

Active Member
gtirx2 said:
LOL you have even got me thinking now:doh: :lol: ,do viscous diffs have a power rating that they can handle depending on fluid thickness and air bubble size?
For instance if the center diff in the R was only rated to say 300ft/lb torque and you was running 400++ft/lb would the torque split still be 50/50? as where you have to much power for the diff to cope with would it not just spin the power away at the front where the center diff is not capable of handling the extra torque making the torque split more like 70/30?
Thats if you understand what i mean as i think i could be confusing myself here:lol: :doh:
Click to expand...
And to think, the bloke only asked where the front diff was!!! I've got a headache just trying to get my head around that above statement! :lol: :doh:
 
gtirx2

gtirx2

Active Member
warringtonjack said:
And to think, the bloke only asked where the front diff was!!! I've got a headache just trying to get my head around that above statement! :lol: :doh:
Click to expand...
I still haven't got my head round it, i could well be talking shite, i am just not sure yet:lol: :lol: :? !
 
K

kingy

New Member
Well all of thats just gone over my head PMSL
well my bro has decided on going out today and getting himself a new car seeing as i was unable to sort it out this weekend.
The car was Grays old one and seems a shame to be sat doing nothing and i know what my bro is like it will end up scrapped unless i sort it out very soon.
Do i need to make a poll to see where the front diff is located?
Imagine what all this will read like to someone that does a search for "where is the front diff" ha ha ha they will be as confused as me.
Looks like i will have to travel to his house to jack the car up and have a look myself.
Thanks for the discussion anyways.
 
gtirx2

gtirx2

Active Member
I said right at the begining of the thread the front diff is in the transfer box.
Most people proberly have not replyed because we are not sure what your problem is,the front diff in the transfer box is usaly pretty tough and don't normaly break,tbh i don't think i have heared of many breaking at all maybe 2.
Try explaining better what is going on,is it still making the noise when coasting in neteral,does it get louder if you turn one way or the other when moving?
 
boucherie

boucherie

New Member
1) Trip
2) str_motorsport
3) JPWard (1 OS upper) The one that is on the driver side and is also higher than the rest
4) Krikra
5)KF79GTIR Dependent on price.
6) Bart GTI-R ((1 OS upper) The one that is on the driver side and is also higher than the rest) Dependent on price!!
7) scotchie
8) Boucherie (only need the o/s upper and rear one as already got the n/s gearbox one)
 
J

jameswrx2

Member
I have the profec B in my gtir, seems a perfectly fine bit of kit.

I like the AVCR but found it a little bit to much faffing around.
 
K

Keira

New Member
simon sent off a centre diff to see about the viscous fluid being changed, theres a few companies that can do it...They tested the standard unit and said 'tbh, its pretty good, anything we can do wont change it really'

i cant remember what they rated it to, maybe si can if he reads this thread, i cant be bothered to ring him to find out :lol:

we do have a plan b, which si has done already but didn't end up using due to a slight technical hitch :lol:
 
K

kingy

New Member
I certainly aint no dumbass lol
I am a mechanic an have done a few gearbox changes on my old pulsar. I only asked on here where the diff is located as it would have meant me traveling to my bro's house and then getting the jacks out and stuff. If i know for deffinite that the diff is in the transfer box then it means i can just get a replacement and then fit it at work.I mean they are only 30-40 quid.

Anyway as someone asked about the problem.The car makes a real bad graiting noise when driving, it makes no differance if freewheeling or under power.To discribe the noise i would say imagine a really bad C.V joint x 10 clicking and graiting that is what the noise sounds like.
I raised the car up on the 2 post ramp at work and got bro to drive the car on the ramp while raised there is no noise at all when driving upto 50mph but the drivers side front wheel wasn't spinning, so i put my foot against the passenger side tyre to offer some resistance to make the drivers side spin as soon as the drivers side started spinning the clunking and graiting started once i let go and the drivers wheel became stationary the noise stopped. This is what lead me to think it is the front diff at fault.
Would you suggest the same ??
 
K

Keira

New Member
you can inspect the front diff by taking off the end casing of the transfer box and pulling the diff out, you need to lose the driveshafts from both sides and the 2 end brackets but if you have access to a lift it wouldn't take very long, would be easier than changing the whole lot, if it is the front diff you've only got to then slide in another diff and shim up the bearing as opposed to swapping the whole lot ;)
 
Last edited:
gtirx2

gtirx2

Active Member
I would proberly say yes it may well be the front diff altho i have never heared of many brecking.
I think its normal tho for only the passenger wheel[and the backs] to spin when its in the air with all four wheels off the ground because of the open front diff.
Maybe he has took a tooth of one of the plant gears or what ever they are called in the diff.
You could try draining the oil out of the transfer box to see if there is any metal in it?Or maybe you could take the front drive shafts out and take the end cover off the transfer box with the front diff in and try and pull the diff out a bit to try and get a look at it?Trouble is i am not sure if there is anuff space to get the cover off because of the chassis leg,you will have to have a look.
TBH the front diff is a simple looking thing and you should be able to see if there is anything wrong with it if you can just get a look at it.
 
Last edited:
You must log in or register to reply here.
Top