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Using 4wheel steering pump for oil cooler

Thirsty

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Sep 6, 2007
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53
Location
Brisbane, Qld, Australia
G'day.
I am removing the 4ws pump from the diff of my GVR4 to take off 4WS as I will rally the car.
Have a thought to use the pump in situ as a circulating pump for am oil cooler on the diff. Any thoughts.
Pump moves about 10cc per revolution.
Cheers
Ross
 

fuel

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Feb 23, 2009
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2,165
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Toronto, ON, Canada
hey Ross sounds like a good idea, but I think you would be better off fitting a plate type rear LSD and then just fit an electric oil pump. Keeping the factory 4WS pump means you can only use an open or viscous LSD rear diff which is not as good as the plate type LSD. Also another point worth considering is the viscosity of differential oil is much thicker than power steering fluid and that pump could indeed be strained and end up heating up the oil even further.

Can you tell us more details about your VR-4? Ie is it J-spec or AU-spec? Where in Brisbane are you?
 

Thirsty

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Sep 6, 2007
Messages
53
Location
Brisbane, Qld, Australia
Was the 4WS pump only on Viscous Diffs?
I thought a viscous diff would be like an open diff till it was loaded. Even turning the rear wheels by hand on my 1989 'J' spec when it is on jack stands, I have both rear wheels turning at the same time, it is really tight to stop one turning.
Car has a good cage that has to be gussetted in the door x's.
I will run my old engine, it has another season in it as there was reduced use last and this year. %
50mm Drummond 'old school' on the front, 50mm Drummond adjustable on the rear. Twin pot Evo brakes and standard with good pads and regularly replaced rotors on the rear, Autronic SMC with soft anti-lag.
Cheers
Ross
Northside, bit to the West.
 

fuel

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Toronto, ON, Canada
yeah the gear which drives the 4WS pump does not fit on the plate LSD diffs, only on the viscous and open diffs. You may have to remove the rear cover to confirm what diff you have.

I'm in West End, originally from New Zealand (have only been here a few months really) - have only seem a handful of AU-spec models (all maroon) so far.
 

cheekychimp

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Apr 19, 2004
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East Sussex, U.K.
Quoting fuel:
hey Ross sounds like a good idea, but I think you would be better off fitting a plate type rear LSD and then just fit an electric oil pump. Keeping the factory 4WS pump means you can only use an open or viscous LSD rear diff which is not as good as the plate type LSD. Also another point worth considering is the viscosity of differential oil is much thicker than power steering fluid and that pump could indeed be strained and end up heating up the oil even further.



Thank you for that, that is very good information. I have been thinking about doing this for a long time to supply a small rear diff cooler. You just saved me a lot of trouble and that inevitable "Oh for f***'s sake!" that would certainly have ensued after I got everything back together and found the pump gear wouldn't work on the plate diff.

That said, I seem to remember my first VR4 when I bought it had a 4 bolt rear end (E38A perhaps), but I thought that the RS cars had a plate rear diff?.
 

fuel

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Toronto, ON, Canada
E38A RS have plate LSD, E39A RS (yes they do exist) have viscous LSD. All RS models from 89.10 onwards got the 3.909 ratio 4 bolt rear ends - earlier pre-facelift models were 3 bolt 3.545 rear ends. Non-RS and non-Evolution 89.10 facelift may have got the 4 bolt viscous LSD 3.545 rear end but I am unsure. 90.05 Evolution models got the 4 bolt 3.909 rear end - plate type for E38A and viscous for E39A.
 

DR1665

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Iowa City, IA
Ross! Long time no see! Hope the holidays treated you well this year, mate. /ubbthreads/images/graemlins/smile.gif

Am I correct in understanding it would be possible to retain the 4WS pump to feed a cooler for the rear viscous LSD?

I think this is a pretty neat idea, although I wonder if the performance/longevity benefits would outweigh the risk of additional complexity under the car. What are you plans for routing/protecting the lines and cooler back there?
 

fuel

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Feb 23, 2009
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Toronto, ON, Canada
yes if you have a viscous rear LSD you could retain the 4WS pump but it would be questionable if the pump would like the massive change in oil viscousity between thin power steering fluid (ATF) and thick differential oil. When pumps get strained they tend to heat up the oil massively, which could negate the efforts to cool it down.
 

cheekychimp

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East Sussex, U.K.
Quoting fuel:
E38A RS have plate LSD, E39A RS (yes they do exist) have viscous LSD. All RS models from 89.10 onwards got the 3.909 ratio 4 bolt rear ends - earlier pre-facelift models were 3 bolt 3.545 rear ends. Non-RS and non-Evolution 89.10 facelift may have got the 4 bolt viscous LSD 3.545 rear end but I am unsure. 90.05 Evolution models got the 4 bolt 3.909 rear end - plate type for E38A and viscous for E39A.



That explains a lot then. So my car was probably an E39A RS and some enterprising individual threw in a plate diff and left the the 4WS intact with no gear running the pump. No wonder it felt so weird.
 
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fuel

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Feb 23, 2009
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Toronto, ON, Canada
What year is yours and what is the full model code as per the chassis build plate on the firewall (ie E-E39A-SNPF), or alternatively PM me your chassis code (ie E39A-0024924) and I'll look it up in CAPS to confirm what model it is and when it was assembled. Yours is a JDM model right?

From what I understand the E39A RS models were mostly used by the rally teams - I have not seen one under private ownership yet. Sure yours is not an Evolution E39A (remember not to be confused with RS) or just a regular E39A with bits swapped on?
 
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cheekychimp

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It could be anything. I would be interested to find out what it started life as. I am suspicious it was actually an auto converted to manual. Probably just a mongrel as you suggested. I'll send you the chassis code tomorrow, can't get the build plate number until later.
 

fuel

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Wont be an rs if it started out auto
 

Thirsty

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Sep 6, 2007
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Location
Brisbane, Qld, Australia
G'day Brian
You well?
Happy New Year to all the yanks, fellow VR4 owners/lovers.

I read up on vane type pumps. The VR4 one pumps just under 10cc per rev and generally vane pumps will handle up to 500 cSt viscosity oil. Synthetic diff oil at 90 weight is only about 160 cSt. Power steer fluid is 37 @40c and 7 @ 100c. That is a big jump to to diff oil..
Think I will just blank it off for now, use it in the new build. The old diff in the wrecked VR4 had lasted three seasons, and is getting a bit loose.
Cheers
Ross
By the way do viscous diffs free wheel {open} when just turning and lockup under load?
 
Last edited:

fuel

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Toronto, ON, Canada
A worn viscous will act like an open diff when jacked up. Mine has a worn viscous and certainly doesn't act like an LSD when I jack the rear up and spin the wheels. I would really like to swap in a plate LSD center and use an electric motor or electric pump and controller for the 4WS. I wouldn't mind being able to turn 'off' the active 4WS at times.
 

Thirsty

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Sep 6, 2007
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Brisbane, Qld, Australia
G'day, opened the diff yesterday, it is a plate diff /ubbthreads/images/graemlins/applause.gif and has the gear drive for the 4ws pump in as the car had 4WS.
Cheers
Ross
 

fuel

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Feb 23, 2009
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Toronto, ON, Canada
Pics?
 

Thirsty

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Sep 6, 2007
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Location
Brisbane, Qld, Australia
Yes here we go...

/ubbthreads/images/graemlins/cool.gif
 

RedTwo

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Jul 16, 2008
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New Zealand
Looks like a viscous LSD diff to me...


From left to right: Open 3 bolt, 4 bolt viscous, 4 bolt mechanical/plate.
 

Thirsty

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Brisbane, Qld, Australia
G'day, My Bad!!! /ubbthreads/images/graemlins/frown.gif...Learning every day....
So is the viscous coupling in at the ring gear end of the diff?
Cheers
Ross
 

fuel

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Feb 23, 2009
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Toronto, ON, Canada
The 'viscous coupling' between the left and right rear axles is in that center housing you see between the crown wheel and the gear to drive the 4WS pump. As you can see from the pic RedTwo provided, there is physically no room to put the 4WS pump drive gear on a plate LSD diff. Your viscous coupling must either be new or modified somehow so it locks up better.
 
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