D1 auto - overdrive kick in point

Printable View

Show 40 post(s) from this thread on one page

13th August 2008, 08:11 PM
DiscoDan

Quote:

Originally Posted by nice1guv

Ok, now I'm really confused.

Keep it below 80km/h and no overdrive or lockup clutch, hit 80 and it feels like another gear (like an electronic overdrive I had on another car) and the revs drop heaps.

On my car at least, it certainly doesn't happen at 45km/h under light throttle or at another speed - only 80km/h and above.

If you drop below 80 it kicks out and the revs go up. The car has more power before it kicks in at 80, so if I want to burn up a hill (on-road) at 90 it will be in " overdrive" and have not much power, if I manually shift it back to 3 then I'm in third and the revs are too high at 90. I want to be able to hold it in 4th with out it going to "overdrive".

As stated it isn't another gear or overdrive. The torque converter has a lockup in it that kicks in at 80kph. The revs drop because the torque converter is slipping. This drop shouldn't be too much from memory it is 100-200 rpm in my car. You will get better fuel economy with it locked. And the power should still be there as the drive train is locked up.

The D2 locks in both 3 & 4 gears. or so I have read and will find out soon.
13th August 2008, 08:13 PM
Romulus

my understanding of the LR D1 auto is its a 4 speed box, period. 1,2,3 & D which is '4th', no additional 'overdrive' as such, am I correct with this? :confused:
13th August 2008, 08:40 PM
nice1guv

Quote:

Originally Posted by B92 8NW

Fourth gear is an overdrive as the ratio is 0.728:1.

On a V8 automatic the 3-4th shift according to the workshop manual occurs between 43-49 km/h on a light throttle 1430-1650 rpm.

Find a flat road, wind it up to 60km/h in D on a light throttle - shift back to 3, then back into D. Do it a few times - as you return to D each time, you will feel it picking up 4th gear which as stated above is an overdrive.

At 80km/h, the lock up clutch in the torque converter engages which feels like another gear as you say and the revs drop considerably. It will only lock up when in 4th (overdrive) gear.

The issue of having not enough power on hills when its locked up and over revving in 3rd is an inherent problem with these gearboxes.

That is exactly what happens.

Excellent! I understand fully. Thanks.

Now, how can I change it?

How does the clutch engage on the torque converter? It must have something that controls it coming in at exactly 80?
13th August 2008, 08:47 PM
B92 8NW

Quote:

Originally Posted by Romulus

my understanding of the LR D1 auto is its a 4 speed box, period. 1,2,3 & D which is '4th', no additional 'overdrive' as such, am I correct with this? :confused:

Yes. There isn't any additional overdrive unit on or anything like that, but 4th gear [0.728:1] is an overdrive by definition
13th August 2008, 08:48 PM
nice1guv

Quote:

Originally Posted by Romulus

my understanding of the LR D1 auto is its a 4 speed box, period. 1,2,3 & D which is '4th', no additional 'overdrive' as such, am I correct with this? :confused:

My LR D1 auto V8 has 1,2,3 plus D (or 4th) plus at 80km/h the clutch locks the torque converter (now I know that -thanks B92 8NW) and it seems like "overdrive".

It certainly doesn't pull as hard with the torque converter locked, and if you give it some curry in D it goes straight from third to 4th locked, basically jumping 4th not locked.
13th August 2008, 09:03 PM
B92 8NW

Quote:

Originally Posted by nice1guv

That is exactly what happens.

Excellent! I understand fully. Thanks.

Now, how can I change it?

How does the clutch engage on the torque converter? It must have something that controls it coming in at exactly 80?

You can't do it easily. A trans rebuilder might be able to change it for you by increasing the spring pressure on the lock up valve, but by having it unlocked for longer, heat generation becomes an issue and the potential to wreck the autobox becomes very real.

A better solution is a mod to the valve block to enable lockup in third.
13th August 2008, 09:15 PM
nice1guv

Quote:

Originally Posted by B92 8NW

You can't do it easily. A trans rebuilder might be able to change it for you by increasing the spring pressure on the lock up valve, but by having it unlocked for longer, heat generation becomes an issue and the potential to wreck the autobox becomes very real.

A better solution is a mod to the valve block to enable lockup in third.

Won't lockup in third do the opposite of what I want? Won't it just make it weak in third and fourth then?

Hmmm....unforntunately I think it might just have to stay as it is.

Oh well, I did want a manual to begin with but couldn't find a good one over here with the other stuff I wanted. So teach me right for not waiting for the manual, although in the last year I have had the auto I still haven't seen a manual I want more.
14th August 2008, 05:55 AM
RonMcGr

Quote:

Originally Posted by nice1guv

Won't lockup in third do the opposite of what I want? Won't it just make it weak in third and fourth then?

Hmmm....unforntunately I think it might just have to stay as it is.

Oh well, I did want a manual to begin with but couldn't find a good one over here with the other stuff I wanted. So teach me right for not waiting for the manual, although in the last year I have had the auto I still haven't seen a manual I want more.

As I said before, it is hydraulic.
That makes the ball game difficult.
It is not like a Falcon, etc, which is electric, unfortunately..
14th August 2008, 02:08 PM
nice1guv

Quote:

Originally Posted by RonMcGr

As I said before, it is hydraulic.
That makes the ball game difficult.
It is not like a Falcon, etc, which is electric, unfortunately..

Ok, forget the auto box... appears just too hard to alter the clutch lockup speed.

What about a switch to a manual box?
I would obviously have to pay someone to do this job, but is it practical?
Would I be better to start again with another disco, this time manual?
Or since the auto car I have has everything else I want, should I look at a switch to manual on this car?
14th August 2008, 02:33 PM
Grimace

I understand exactly what your after.
I too wish that LR used some sort of load sensing to disengage the lock up above 80 if excessive load was endured (steep incline etc etc).

I regulary find myself wishing it would just unlock for a incline when doin 110klm just so it held the speed better. But no, if the climb is steep enough, you loose more and more speed until the auto thinks 'I might just change into third...' downshifts, revs go up, speed is gained then wham back into 4th lockup, speed drops, so again it jumps into third :mad:

Really annoys the **** out of me, specially when i know it would just hold the speed in 4th no lockup.

Something we just have to live with :mad:

Show 40 post(s) from this thread on one page