Diff oil in front shocks.

[S14x]

Right I have some time on my hands today (thank god) to work on my poorly Volvo 340.

How do I replace the oil in my front shocks to EP90 diff oil to stiffen them up..

Sorry for the some what stupid question.

Thanks in advance for any replies.

[thododd]

Youll need to start by removing the strut;
so jack the car up and pop it on stands
Wheels off
Undo; ball joint, steering arm, top mount and take the caliper off the brake disk.

Remove the strut from the car and then having compressed the springs, you can undo the damper top nut and remove the top mounts, bearing, upper spring seat and springs from the strut assy.

When you undo the damper retaining nut youll be presented with either of the below dampers


The one on the right is a cartridge/insert sealed unit so youll need a new plan if youve got these

The stuff on the left is what you want. When you remove the damper retaining nut the oil in the system can escape (this will be your first indication) so once youve taken the assembly from the strut body and drained the remaining oil, put the dif oil back in and rebuild the strut in the reverse of the above procedure.
Remember what order everything comes off the damper spindle and be careful with compressed spring ... best of luck, let us know how you get on. We always like pictures

[S14x]

Youll need to start by removing the strut;
so jack the car up and pop it on stands
Wheels off
Undo; ball joint, steering arm, top mount and take the caliper off the brake disk.

Remove the strut from the car and then having compressed the springs, you can undo the damper top nut and remove the top mounts, bearing, upper spring seat and springs from the strut assy.

When you undo the damper retaining nut youll be presented with either of the below dampers


The one on the right is a cartridge/insert sealed unit so youll need a new plan if youve got these

The stuff on the left is what you want. When you remove the damper retaining nut the oil in the system can escape (this will be your first indication) so once youve taken the assembly from the strut body and drained the remaining oil, put the dif oil back in and rebuild the strut in the reverse of the above procedure.
Remember what order everything comes off the damper spindle and be careful with compressed spring ... best of luck, let us know how you get on. We always like pictures

Wow thank you for the information

[Joris]

with how much oil should you fill it?

[mac]

Joris - 320ml per side.

S14x - May I ask why you wish to use EP90 in your dampers?

I presume you understand the principle of road spring/unsprung weight oscillation control and have correctly matched your (new?) front springs to the damping characteristics you expect by the use of 90 weight. New springs are obviously ordered by weight (lb'age) but I would love to know if you have found an easy way of determining the oil weight when retaining the standard valving.

If by any chance you are retaining the standard springs you may well perceive an increase in compression stiffness - but with standard valving you will find rebound to be too stiff resulting in "wheel pick up" and potential loss of grip during front lift. Rebound after check braking in mid corner could give induced understeer.

Sorry if I'm "teaching granny to suck eggs".

Mac.

[classicswede]

And I am fairly sure a fast drive over a bumpy road wil result in the oil foaming and result in the damper locking. I am surprised how common practice changing the oil is.
It is your choice to do but at least be aware of what you are doing and be certain that your driving ability will allow you to control such conditions. At least on a race track everyone should be going the same way.

[thododd]

Whats the viscosity index of the original oil in the system? And the OE spring rates?

[mac]

OK - lots of info!

The VI of the standard damper oil is around 185 for 340s and 170 for 360s but remember VI is an arbitrary number indicating the ability of an oil to change it's KI in response to temperature.
Of more use is the SAE viscosity (the measure of "thickness" and the 10 and 40 of a 10W40 engine oil) this is equivalent to the KI - the Kinetic Viscosity!

For a standard 340 the OE damper oil would be about 5 @ 40c and the equivalent of 22 @ 100c. The 360s would use an oil of about 6 or 7 @ 40c and 30 @ 100c.
An "up rated" damper oil for use with, say, 180-200lb springs would use around a 9/45.
Also do not forget that damper oil will have a dedicated additive package - especially anti-foaming which diff oil will not!

But - as I've said the damper characteristics need to be matched to the unsprung weight oscillations and spring rate.

You will note from the above that a 90 weight oil will be rather "thick".

Now - as for the rating of the standard 300 front spring - given the wire diameter, number of coils, free length and overall coil diameter (less x1 wire dia. Of course) it's an easy calculation to make - we arrive at:-

B14 up to 78 = 87lb.
B14 79 on = 98lb.
D16 = 110lb.
B172 = 110lb.
B19A = 139lb.
B19E/B200 155lb.

Mac.

[thododd]

Diamond mac, cheers.
Good info to know.... itd be a cherry on the cake if you knew rough corner weight figures for a standard 360

[mac]

A rough estimate for a stock 360 is (in kg) with a 56/44% distribution dry
(A 340 would be a little lighter (by 30kg or so) and nearer 53/47%)

F 311/311
R 245/245

Both variants have a fairly high polar moment.

Mac.

[S14x]

Its what I've been told to do. Putting thick diff oil in them to stiffen them up rather than buying uprated ones.

[mac]

I understand it's what you've been advised to do - if your adviser is a suspension design engineer then go ahead - sorry to have voiced an opinion - but if not, ask them the rationale behind using EP gear oil in a damping system. Excessively stiffening spring dampening can reduce grip not improve it (off brake lift induced understeer) and destroy turn in.
Not good for road or track days, and if drifting, the front is the last end you want to loose grip with - it's oversteer you need to dial in.









But then what do I know ??
Mac.

[LadbrokeOB]

Can anyone recommend a decent hydraulic fluid that would replace the standard shock absorber fluid?

Im just asking as I was about to put gear oil in mine, but read about the problems with frothing and locking up.
Essentially im just looking to make the shocks stiffer on a budget and need to locate a heavier fluid that doesn't froth!

[360beast]

Why not replace them with KYB gas shocks? They're only about £15 a pair, chances are the reason they are soft is cause they're more than likely 20+ years old.

[LadbrokeOB]

I have an '88 340, and from what I can tell it seems like they aren't cartridge types. :/

If i posted a picture of the piston and cap nut would you be able to tell what type they are or do i need to open them up to have a look?

I keep reading different things about inserts etc.