Thread: 4HP24E into Disco 1 V8

I was interested to hear how this went. I heard it was a drop in fit despite the different dimensions of a 4HP24, and it was also possible to use a 4HP22 hydraulic valve block instead of using a TPS and compushift (or other controller). How did it go in the end?

Damien

The 24 is a touch longer?

G'day Damien,

I'll post a proper follow-up with pictures as soon as I get a few spare moments. I was a bit surprised that many looked but no-one had anything to add as this didn't seem a far-out thing to do...

In a nutshell, though, I found the following.
Firstly, the correct/matching flexplate/flywheel assy must be used, and the overall trans is 15mm longer which drives a few minor issues.
Shifter cable could re-used as-is. Just needed a bit of an adjustment.
Transfer case mounts needed to be modified both sides to shift rearwards in the vehicle.
Trans to transfer case pencil brace needed to be extended. Dipstick tube bracket reprofiled to meet the bellhousing fixing point.
Output shaft of the trans needed to be shortened by 4cm, and the shaft redrilled and tapped (to accept the trans to transfer case adaptor shaft and fixing bolt). The circlip and bearing collar also had to be removed (behind the park pawl).
P38 XYZ switch used for neutral start (inhibit) and gear-sensing for the CompuShift.
Oil cooler lines needed to be modified (the trans-end is a different size and type fitting). I cut off the P38 ends and brazed them into my D1 lines.
All of the above was no great drama. It just chewed up a bit more time as I had access to plasma-cutters, welders, oxy, cutting and grinding tools and the basics you have in a proper mechanics workshop.

I will need to shorten the rear prop shaft by 15mm - I've estimated there is juuuuust enough plunge left (probably?) but it's pretty marginal and squashes the rubber boot a bit currently.
I have ordered a 15mm front prop-shaft spacer to get the front shaft back to the correct length.
I will wire my existing reverse light circuit into the Compushift dedicated output (I have no reverse lights currently).
I will wire my speedometer into the Compushift TOSS output (my speedo/odo were always inaccurate due to tyres, etc. and I can get a perfect signal out of the Compushift). This one I don't have to do, but why not?

Quick summary of end result:
Very pleased overall. I can fully tune all of the shift points and firmness and TCC engage, etc, etc. I can run multiple selectable maps and have full manual control over the TCC and use it in multiple gears. I can even hook up paddle shifts for full manual control if I ever feel the need. My stall speed has dropped from a ludicrous 2700rpm to a near-perfect 2050rpm with the "big-boy" M19 torque convertor. My engine puts out a healthy 310 lb.ft (420Nm) at 2000rpm so the standard D1 convertor couldn't hold it as it was designed for only 200 lb.ft (270Nm) at the same revs. Also, Wholesale Autos in Bayswater gave solid tech support when I ran into a glitch and I would recommend them.

More to follow in a few days...

Edit: Thanks for the great writeup.

Bellhousing is longer right, but is the governor slightly shorter?

Note to use the 22H valve block on a 24EH you would need to install the kickdown cable, cam etc, and make sure alignment was perfect. I think you went the right way.

In a nutshell...
The bellhousing and maincase are about the same (however the EH case isn't drilled for inhibitor switch, TV cable, etc).
The pump housing is 15mm thicker (higher capacity pump).
The governor housing is quite different with the 22H being much shorter (different transfer cases used). I didn't measure this as I couldn't use the P38 one anyway.

I did look at, and originally planned to, build a heavy-duty 22 using 24 internals, however I decided that the extra benefits from having full control of the EH outweighed the cost savings. Plus I had a well-maintained, low-mileage -061 'box from a known, trusted source that I didn't need to break apart or rebuild or do anything to. Additionally all of the interface stuff I would have had to do anyway (trans mount relocation, oil cooler lines, etc) so the installation wouldn't have been any easier (notwithstanding having to wire in the controller).

Ashcrofts site have really good info on the 22 and 24 differences, and Compushift.

One thing worth noting is that the EH 'boxes are either fitted with a P38 or D2 XYZ switch. These are quite different and use different protocols so are not interchangeable. The D2 switch has reverse switching as well as inhibit and gear position (ten wire), the P38 one (five wire) doesn't have reverse switching (it's done through the body computer). My Compushift was supplied set-up for a D2 switch (calibration and wiring) and this was the glitch I required tech support with as the wire labelling was then wrong. Once I understood that was the case I rewired the patch harness and told the controller I had a P38 switch and everything worked perfectly.

"embiggened" , very understated
can you speed up the manual downshifts?
I find it takes long seconds to shift when I manually change down from 4 to 3. whereas kickdown is nearly instant.
?

Hi Peter,

I haven't spent that much time with it as it's not my daily drive and life keeps getting in the way of playing with my toy. However the few manual downshifts I've experimented with seems to be about as quick as the old 22H. Not super fast, but reasonable. Maybe about a second or so, certainly not long seconds.... Certainly tuning the shift pressures seems to speed things up a bit both ways With the standard shift cal (as supplied) the shifts are a bit slow and mushy with a run-through bump at the end (not entirely surprising the extra torque I have over a factory 4.6) and similar to the old 22H, but with a bit of a rejig they are firm and robust without being harsh.

If you have slow downshift like this your 4/3 TV spring may be broken. Next time you have the filter off have a look up at the lower (smaller valve block) and see if the springs look OK.