SLROC Forum

Folks I'm going to change my manual LT85 to an auto from an N reg (96) 3.9 disco donor I have.

The original plan was to transplant the complete serpentine engine and box and EFI from the disco into the 90, but I've decided to stick with the 3.5 and twin SU's for now but the LT85 is on its way out and I want to swap the boxes over sooner rather than later.

I can forsee a couple of issues with the speedo and the kick down as I'm not using the EFI setup and there isn't a linkage on the carb manifold for the kick down cable.
I'm sure I'm not the first on here to do this conversion, does anyone have a previous solution to the above issues?

There is also the issue of mounting the gear selector but I'll make a console or something to hold the shifter in place.

Cheers

In all honesty it will be easier, quicker and  probably cheaper putting the whole lot in from the disco (if you are ultimately swapping the engine anyway). And depending on the condition it should be more powerful too!

If you want to swap the boxes; You really need a 3.5 torque converter as well as the kickdown linkages (if you can find some). Speedo should be fine as the transfer box goes straight back on the auto box. Need to sort out the cooler for the box, maybe use the disco rad pack.

To swap the whole lot you will need a fuel pump, possibly new speedo cable (take the tranducer off the disco), tune resistor if going to non cat, tubular RRC V8 gearbox crossmember, and then obviously the wiring loom and ecu out the disco (which I would recomend thinning down of all the circuits you dont need).

There will be other things I've forgotten but having effectively done the same thing converting my 3.5 carb RR to Efi serp it's a bit fresher in the mind and I'll probably remember more later

whoops, wrong post 

Thanks for the reply, the plan was to swap the lot over in a one'er but ideally I want to rebuild the 3.9 over the winter and fit the lot in the spring, but I don't think my manual box is going to last much longer, so fitting it to the current lump was a stop gap measure, but may be a non starter, I just assumed that the torque converter would be a straight fit.

Initially i was going to use the EFI from the disco but for simplicity I'd prefer to keep it on carbs and getting them re jigged for the bigger engine as its more of a mud / green road toy than a road car.

The reason I mention the torque converter is that they are sized differently for the shift points, the autobox may be valved differently too though I am not 100%. Don't get me wrong it will work, but it could end up with funny characteristics/needing to rev the hell out it to change gear.

Its up to you, the EFI system is not complicated and will give much better pickup with the autobox. Its getting the linkage parts for the carbs that will be awkward.

and do not drive the auto box without the kickdown cable attached and adjusted, you will damage the gearbox.