Auto Transmission Problem?

[blazza13]

Hey All,

I think I might have a problem with 96 Discovery Auto transmission, the problem being that when it changes from 1st to 2nd or 2nd to 3rd (both holding 2000rpm) it slightly slips between changing. I've had a look at the Transmission fluid and its at the correct level, this problem really only started when i pulled off the throttle assembly. Which makes me ask the question about the cable that sits under the throttle cable on the throttle mount, does this cable go to the transmission? And if I might have accidently adjusted it, would this cause the problem or something else?

Blazza13

[PhilipA]

Yes.
The kickdown cable controls the revs/throttle position of when the transmission changes.
If you have reduced the adjustment , the transmission will change at lower revs and with less line pressure/more clutch slip.
Just adjust it a bit so that he lead "slug" is say 2 MM further away from the outer cable end. The correct amount is in the manual , but about 5-7MM is normal.
If you want sharper chnages at higher revs, adjust it with a bigger gap.
I am sure this will do no harm. Just adjust it to your preference.
Regards Philip A

[George130]

Adjusting the kick down shouldn't do any harm. It will just affect how agresive or sedate it is.

[Blknight.aus]

yes, you have a problem you have an auto... Ok Snipe done...

changing the throttle sense setup will change it a little bit but not gargantuanaly.

If you set it up so that it shifts early it will also shift with a little less "grip"
set it up so it shifts late and it will "grip" harder.

however it should not affect the speed of the change.

In theory you should not be able to tell the difference from driving but if something else is out of whack, It can be the straw that broke the camels back..


When was the TX last serviced? did they change the filter? Have you had the boxes internal oil pressures checked?

[blazza13]

Thanks too PhilipA comments, i have solved the problem... I adjusted the kickdown cable by accident... Adjusted it back to what PhillipA said and now it's smooth as silk!

[BigJon]

If you set it up so that it shifts early it will also shift with a little less "grip"
set it up so it shifts late and it will "grip" harder.

however it should not affect the speed of the change.



Expand and discuss...:D

What do you mean by "grip" and the speed of the change.

[Blknight.aus]

by Grip I mean how much pressure is exerted by the hydraulics inside the box to effect the bands or the clutvh packs.

Think of it like using the clutch on a manual. (very very pallpark,)

If you change the gears correctly (once the vehcile is moving) weather you ease up the clutch over a 5 second period or a 1 second period you shouldnt be able to tell the difference in the change. (as in the vehicle wont jerk around due to miss matched engine rpms to road speed)

This equates roughly like this, if your doing race changes (late shifts) you want to be fast on the clutch to get the power back on (more grip) if your taking it easy because you carrying a load of unstable nitro (early shifts) you'll be easier on the clutch (less grip)

In an auto when it shifts late it increases the pressure to the actuators, when its shifting early it applys less (and backs off when coasting)

Shift time is how long it actuall takes to change the gear, in a manual this is akin to how long it takes you to move the gearshift from one gear to the next.

In an auto these things are related but in fault finding its how it fails that counts...

IF when it goes to change gears it takes bloody ages to get the next gear (but gets the correct gear without slippage when it gets there) then the hydraulics are clogged, so the fluid takes a while to fill the actuators but eventually fills them to the correct pressure

If it never changes properly then youve got pressure problems (for various reasons) and the bands or clutches dont get actuated fully

If it slams into gear its overpressure.