Thread: D1 auto - overdrive kick in point

Originally Posted by justinc

These are the options as I see them;


1 Convert / moidify the valve body to have 3rd and 4th lockup.

2 Lighten the governor weight to change lock up (and all shift points) later

3 Install a later 4HP22EH from a D2V8 and use a compushift ECU

4 Install a 4.6 or 5.2 litre engine that will pull up any hill in OD

As Grimace pointed out, it is a product of old school hydraulic operated autos, and is a part of D1 life....And believe me, it gets worse when you have a Tdi infront of it

JC

I'll take the 4.6 thanks!

But what about a changeover to a manual?

Easy for the right person to do? or is it messing with an already mated combination? Would I be better to buy a manual and improve everything else, or switch over the auto with most other things already done?

how much money do you want to spend?
the 5 speed should bolt straight in,
the 4.6 might need a different box as well? 4HP24?


Its a bit strange seeing Ron talk about WANTING electrics

Originally Posted by Pedro_The_Swift

how much money do you want to spend?
the 5 speed should bolt straight in,
the 4.6 might need a different box as well? 4HP24?


Its a bit strange seeing Ron talk about WANTING electrics

Pedro,

Electrics in old Jaguars and most other pommie lucas fitted cars, suck

Modern electrics are good
I like the clutch lockup in the Foulcan, it drops out under strain and you get extra gain.

Originally Posted by nice1guv

But what about a changeover to a manual?

Fine, just don't tow any thing heavy with it and expect the gearbox to last.
They are a lot weaker than the auto.
(My source? A Land Rover wrecker).

Now I will try to make this as simple as possible but it is a lot more technical to get right than hard to do.

An auto box shifts on Hydraulic pressure and this is measured from the input and the output shafts on most autos including the 4HP22's as well as the 4HP22 also relies on the kickdown cable for line pressure to the clutches including the lock up clutch and I will get back to why in a sec.

To change the shift pattern you would then have to know how to change the shift pressures for each clutch range as Justinc hinted on with dropping the relief valve spring pressure to allow the trans to change into each range (ratio) earlier.

I dont understand why but if you were to want lock up on 3rd to I assume have an intermediate ratio between 3rd and 4th then you would need to save a hydraulic supply to the lock up clutch which could be done possibly with a electrically operated spool valve and major mods to the valve body or drilling relief into the valve body which would also make the change from 3rd to 4th be extremely harsh due to the extra line pressure available to the clutch.

This is where your kick down cable comes into play, it holds pressure on a spring on a control spool which supplies a balance of pressure to the kick down circuit which is controled from the throttle cable and this also controls the pressure to the clutchs to control how harsh the shift will be into each range so it is a mechanical throttle positon sensor so to speak.

It is normal for them to lock up at 80kmh and if there is a huge drop in revs then it may be that your torque converter is tired and is slipping more than it should (as mine is now) and so lock up is a huge drop in revs.

Shift pattern is 1, 2, 3 and 4th which is with the converter slipping at I think about 5% which increases torque but acts like a drop in ratio and then when the torque converter is locked up it goes to 1:1 from engine to gear train which then is at .071:1 or something like that which is an OD ratio.

The converter should only conteract the OD ratio to give approx 1:1 ratio through 4th to the output shaft.

If your not feeling the change to 4th and it doesnt drop out of lockup on load then I would say that your kickdown cable maywell be broken or not adjusted correctly.

Now there is the possability that if it's a V8 it could be a vacuum kick down (one of the V8 guys should be able to fill you and I in on that) then the servo may not be woring correctly or it may have a small leak which will cause similar symptoms.

Sorry it's a bit long and tech heavy but I think some people need to have an understanding of how their auto actually works and I hope it helps fill you in on your question.

As far as a change to manual goes, it's personal choice but I recon that doing a bit of fiddling with you trans and maybe changing the converter would end up being a fair bit cheaper and would result in a nicely sorted drive without having to worry about a clutch.

Thanks for the write up!

Originally Posted by mcrover

<snip> and it doesnt drop out of lockup on load then I would say that your kickdown cable maywell be broken or not adjusted correctly.

I thought that the 4HP22 didn't have the capacity to unlock under load - isn't it simply in or out depending on whether you are over or under about 80kmh?

Originally Posted by B92 8NW

Thanks for the write up!



I thought that the 4HP22 didn't have the capacity to unlock under load - isn't it simply in or out depending on whether you are over or under about 80kmh?

No probs.

No, at 140kmh mine stayed in 4th in the NT as it was under load, too much for the lockup clutch.

If everything is working properly they are great to drive but as soon as things start getting old and clearences get a bit bigger then things start getting a bit lazy and dont do things how they should.

I'm sure RonMcGr's wrecker is correct when he says the auto is stronger than the manual, but can anyone else confirm this?

Cheers mcrover, now I'm thinking maybe just a little adjustment might help things a bit.

But I'd still like to hold 4th with no lockup until 90 or 100km/h, although it seems this may not be possible with the auto box.

mcrover, if you kickdown through the cable (or vacuum) does the auto always drop to third or can it be made to kickdown to 4th no lockup? I'm pretty sure mine always kicks-down to third - haven't tried it at 140 though.