High Revs Changing Gear

[Bludger]

Hi Everyone,

I've got a bit of a problem with my Surf. It has just started revving quite high before changing gear. The first gear change is at about 3000 rpm and it's the same for the next gear change (is that 1st to 2nd & 2nd to 3rd?) you can probably tell I'm a novice!

Anyway, I've read a few threads about topping up the ATF fluid, but I've just checked mine after a good 10 mile run, and it is just a bit over the Top mark, so I assume it's topped up ok.

Can anyone suggest another reason for the high rev's? I have done 20k miles since buying it straight from import in 2005 and have never changed the Timing Belt, so it is possible that it's never been changed! Ouch!

Any ideas will be gratefully received as I'm worried I might crack the head if it is over revving too much.

Thanks All

[KERRSURF]

is the ECT button pressed in?

[dieselboy]

find out when the timing belt was changed and do that before it snaps and ruines your engine..

2ndly, the 4wd hasnt been put into 4wd LOW has it? either that or the "sports mode" is on..?

what colour is the gearbox oil. it shouldnt be overly burnt, and if its more black/brown rather than red it may be best to change it.

[Bludger]

is the ECT button pressed in?

The ECT Button isn't connected, so I don't think it's that, but thanks for the suggestion.

The ATF oil looks pretty good. It's a reddy / brown colour and quite opaque, so no grime or sludge in it.

How easy is a Timing Belt to change? Does anyone know of any instructions on the forum?

Cheers all.

[Apache]

Do you mean translucent?

It should be bright red, not brown, and should not be opaque if its fresh.

[Bludger]

Do you mean translucent?

It should be bright red, not brown, and should not be opaque if its fresh.

It's not bright red. There is a bit of brown in it, and I wouldn't say it's translucent. I have never changed it, so would imagine it's getting on a bit.

Would that have an effect on the gear changes then? Why?

Also, would the timing belt be a reason for the high revving? I don't want to change it unless I have to.

[Apache]

It changes viscosity with temperature and pressure (which is how it works) so if its been boiled or overheated, these properties change so it no longer works properly.

[NiftyNev]

Also, would the timing belt be a reason for the high revving? I don't want to change it unless I have to.

No, but if you have no idea when the belt was changed then do it yesterday, otherwise you may be up for a new engine. I suggest a transmission service as well.

Nev

[dieselboy]

just out of curiosity, and something to check - no one has moved your 4WD lever into LOW ratio have they?

[KERRSURF]

I'm pretty sure he didn't do a 10 mile run in low.


but hey, you never know.

[Bludger]

I'm pretty sure he didn't do a 10 mile run in low.


but hey, you never know.

No, I didn't do a 10mile run in Low Gear!! I did check just to be sure, and no it wasn't in low gear. I have checked a sample of the tranny fluid against some fresh Dex III and it quite literally looks like sh*t !

So I am going to change the fluid this weekend. I've been trawling the forum and the interweb to find a step by step guide, but have only got sketchy instructions. Does anyone know of a thread anywhere that will give a guide to flushing the fluid with the 2 bucket method like in this thread? This thread only give a basic idea of how to do the flush, but considering I don't even know where to find the 2 hoses, I could do with a bit more of a guide and even some pic's if they are available.

Help Please?!

Also, just to show my ignorance even more, I would like to know how the ATF works to change gears. I always assumed tranny fluid was just to lubricate the gears, but it seems it is responsible for making sure the gears change at the correct time. How?

Anyone want to share their knowledge of ATF?

I don't ask for much do I ?!

[CaptainBeaky]

OK, I'll have go...

1. Auto transmissions change gear according to a set profile of load vs revs vs throttle setting vs road speed (all the electronic wizardry that controls your autobox). This is moderated by the torque converter, which is, essentially, 2 paddle wheels in an oil bath, the thickness of the oil transferring the torque from the driving paddle to the driven paddle. The oil also allows the driving wheel to turn faster than the driven, akin to slipping the clutch on a manual transmission.

(Note for Vince and MattF - yes I know this greatly simplified)

2. ATF contains modifiers that alter the viscosity profile of the oil - i.e. how the viscosity changes with temperature. The modifiers are there to flatten out the profile - i.e. to reduce the change in viscosity over the operating temperature range. This will make you gearbox operate more consistently at varying temperatures.

3. If you have cooked the fluid, you will have damaged/broken down the modifiers, allowing a larger variation in viscosity. The upshot will be that your ATF is thinner at operating temperature than it should be.

4. Returning to point 1, the load seen by the gearbox at a particular throttle setting/road speed/loading will be affected by the viscosity. At a lower viscosity, the driven wheel of the torque converter will have turn faster in relation to the speed of the driven wheel, to transmit the same amount of torque.

5. Short version: Change your ATF now!

[Bludger]

Hi Again,

Right. Next problem.

I've changed the transmission fluid this morning, and there is no change with the high revving. I drained about 5lt of fluid, and then topped up with 4ltr. Took her for a quick drive and checked the level. It was in the middle of COLD & HOT so I topped up with another 1ltr to replace the 5ltr I drained.

Still no change. It still revs to about 3000rpm before sluggishly changing gear. When I got home I checked the level again, and now it is above the HOT mark (see picture).

Have I overfilled it, and would that cause over revving, or am I barking up the wrong tree?

Any more suggestions?

BTW. The tranny fluid change took no time at all! I was worried it would be a real ball ache, but it was smooth sailing!

[dieselboy]

the 3.0 litre im driving around in at the mo has the fluid overflilled. it wont cause immediate problems..

im wondering if your auto clutch aint gripping the gearbox side well enough?
obviously you can tell i dont know anything about torque converters or auto clutch setups, but im just tryin to think why the engine will be revving more before the box changes

[BUSHWHACKER]

the 3.0 litre im driving around in at the mo has the fluid overflilled. it wont cause immediate problems..

im wondering if your auto clutch aint gripping the gearbox side well enough?
obviously you can tell i dont know anything about torque converters or auto clutch setups, but im just tryin to think why the engine will be revving more before the box changes

Too much fluid in the transmission is just as bad as too little.
If there's too much, you run risk blowing a hose off due to high pressure amongst other things. Just drain a bit out either from the rad hose or drain plug.