This seems to indicate the trans swap will work

https://landroverforums.com/forum/di...21/#post536617

 

The two transmission models are probably designed to accomodate the unique hp/torque curves for their respective 4.0 and 4.6 engines. Therefore, even though the RAVE manual mentioned "the operation of both transmission is the same", I gather the shifting characteristics may be slightly different. I am not an expert on engine programming or tuning.

I checked Ebay and noticed the TCU part numbers are different for the 1999-2002 versus the 2003/2004s. The former appear to be made mostly in Hungary. The latter in the UK.

It would be interesting to get an update if changing the TCUs would significantly affect the shifting and performance characteristics.

 

What I interpreted from the RAVE was that the 4HP24 has a larger fluid pump to accommodate the higher power output of the 4.6, which makes total sense. The gear ratios are identical but I would agree that shift points relative to throttle position and load would almost have to be calculated differently, which would explain the difference in TCUs. I'm not clear on how "married" the TCUs are to the trans, of if they can be interchanged without issue. I wouldn't think anything would be damaged by swapping them around but I'd hate to find out the hard way. I'm also not clear if any of the other parts of the truck's electronics care about which TCU is there. I don't think there's a relationship like there is between the ECU, cluster and BCU, but I honestly have no idea.

 

I may be spreading misinformation here -- but, I remember something about the Disco frames 99-02 and 03-04 being different, and the sole difference in the frames was the transmission mounting points bt the 2 transmission variants. True?

 

I have a 2003 4HP24 in my 2002 that originally had a 4HP22. LS swap was done at the same time.

4HP24 is about 3/4 of an inch longer than 4HP22. The driveshafts will adjust to make up the difference. The transfer case / transmission mounts I believe are a little further back on the later models, but I was able to make it work (with LS). As far as I know it is a bolt-in / plug-and-play swap.

The 4HP22 TCU will run the 4HP24. There are some differences in tuning, but it's mainly to do with the 4.0 vs 4.6. You can swap out different TCUs as they are not coded to the car/other modules. The early 4.0 TCUs seems to work best with the LS because it holds the gears longer and lets the engine rev higher. 4.6 TCUs don't rev as high and upshift earlier.

I'd stick in the 4HP24, leave your current TCU and see how it goes.

 

You guys are correct, the trans mount location is clearly different and there's a reason this is important when considering a frame replacement. Measuring from the front axle back, the top pic shows that the 2004 has a slot that starts at about 38 5/8" and is roughly 1 3/8" long, ending up at close to 40". Those numbers are approximate due to the fact that the camera angle may have introduced a little skew but I tried to minimize that and take it straight on, so it's likely close enough. The 2002 I measured for the middle pic doesn't appear to have a slotted mount, but I couldn't tell if there was some type of shield on there, and the bolt was in place. It lands at right about 38 7/8" on center. I would not be surprised if it's in fact a hole and not a slot, maybe someone can clear that up.

This appears to indicate that an early trans would fit up to a later frame and the bolt would land right up against the front of the slot, which is odd since the early trans had to be modified internally to handle the power of the later engine so that shouldn't be a desired path anyway. That's the end of the good news however. Each trans mount sits in a small pocket that's welded to the chassis and while the pocket on the passenger side seems to have plenty of room to accommodate a bushing relocate (see bottom pic), the driver's side does not. The driver's side pocket is roughly the size of the trans mount, this is kind of evident in the second pic, so this will probably have to be modified in order to accept the mount in a new position. Not a show stopper by any means but important to know going in if you're not able to fab a workaround yourself.

 

Awesome, this is exactly the feedback I was looking for. Thanks so much!

 

This is all good to know because I intended to do a hp24 swap on the 01 if/when I have to do the 5.3l swap. It's good to know it all bolts up. Same flexplate/starter/everything?

 

I feel like that has to be a mistake? I thought the D1, RRC SWB and D2 99-02 had interchangeable rear driveshafts.

 

They are. I looked into this pretty deeply when I was debating a frame replacement through rovers north for the 2004. I was weighing between a new galvanized or a junk yard frame, and realized quickly that the junkyard route was pretty much a no-go due to the lack of 03-04's that make it there. ALWAYS a 99-02 at a junkyard but it's a rare day when I see an 03-04. Anyway, I digress, the differences were the trans mount for sure, and I want to say something about a hose in the engine bay? I don't remember, but definitely the tranny mounts.