Gearbox issues when warm

[Time Bomb Tom]

I can select all gears easily when cold but when the gearbox warms up it's very hard to get 4th and 5th. It has 75 90 oil and it's filled to the level.
Thanks guys.

[faggie]

run shc oil not cheap but the best

[Time Bomb Tom]

Will this help? What grade?
Thanks

[faggie]

theres only one grade and its very expensive and hard to get hold of but my gearbox is still working perfectly even with my uprated engine

[CJH]

I can select all gears easily when cold but when the gearbox warms up it's very hard to get 4th and 5th. It has 75 90 oil and it's filled to the level.
Thanks guys.

Mine has a similar issue. Changing the clutch slave cylinder and flushing the clutch fluid helped quite a lot, but I've still got traces of the problem. So I've kept a close eye on any threads on here that sound similar, and I've noticed that Aidan often suggests that the spigot bearing can cause this - ok when cold but I'm guessing it snatches once it warms up, and maybe acts like a dragging clutch. Gearbox off job to fix it.

[Time Bomb Tom]

I bled the clutch last night and took it for a 25 mile drive and the problem seems to have dissapeared, aslong as the box got warm enough? Thanks for your help guys.

[kevtherev]

FYI
Clutch and brake fluid should be changed every two years, as it's hydroscopic it absorbs water reducing it's abilities.

[faggie]

unless you fit synthetic brake fluid

[kevtherev]

unless you fit synthetic brake fluid

All brake fluid is synthetic.
Brake fluid is a variant of polyethylene glycol. Since it does not occur in nature, it's synthetic. DOT 3, 4 and 5.1 are polyethylene glycol based. *
..and guess what..it's hygroscopic
So it needs changing every two years.

*DOT 5 is silicone-based and does not mix with the polyethylene glycol based fluids..this fluid is hydrophobic, so this does not need changing regularly..

if that's what you meant.

[faggie]

my mistake the stuff I use must be silicon based as it does not need changing and does not harm paintwork

[kevtherev]

Dry boiling point Wet boiling point Viscosity limit Primary constituent
DOT 2 190 °C (374 °F) 140 °C (284 °F) ? Castor oil/alcohol
DOT 3 205 °C (401 °F) 140 °C (284 °F) 1500 mm2/s Glycol Ether
DOT 4 230 °C (446 °F) 155 °C (311 °F) 1800 mm2/s Glycol Ether/Borate Ester
DOT 5 260 °C (500 °F) 180 °C (356 °F) 900 mm2/s Silicone
DOT 5.1 260 °C (500 °F) 180 °C (356 °F) 900 mm2/s Glycol Ether/Borate Ester

Here is some information taken from the wikipedia

Most automotive professionals agree that glycol-based brake fluid, (DOT 3, DOT 4, DOT 5.1) should be flushed, or changed, every 1–2 years under non-racing conditions. Once installed, moisture diffuses into the fluid through brake hoses and rubber seals and, eventually, the fluid will have to be replaced when the water content becomes too high. The corrosion inhibitors also degrade over time. Degraded inhibitors cause corrosion in the braking system. The first metal to corrode is copper.

DOT 5 is silicone fluid and the above does not apply. Ideally, silicone fluid should be used only to fill non-ABS systems that have not been previously filled with glycol based fluid. Any system that has used glycol based fluid will contain moisture; glycol fluid disperses the moisture throughout the system and contains corrosion inhibitors. Silicone fluid does not allow moisture to enter the system, but does not disperse any that is already there, either.
Silicone fluid is used extensively in very cold climates, particularly in Russia and Finland.