I have an 03 with 123k miles. Out of no where, the trans gave out. No power in any gear, and a grinding when switching to park. Driveshafts are still intact. I picked up an 04 trans with tcase, wiring harness, and CDL shifter linkage. I don't plan on taking apart the trans or tcase at all since they were serviced recently. I see the seals between the tcase and trans, is there a gasket as well? For the bell housing to engine, is there any gaskets/seals? What seals/gaskets do I need to replace and what are they all called? Are there any step-by-step guides to replacing everything?

Some unrelated notes: i recently (<1 month) bought this disco. here's the link to it. service records are on there. previous owner replaced almost all engine gaskets and sensors, new brake lines, other misc. no lights, no oil leaks, and it drove great before that trans issue. haven't done any fluids since getting it. coolant is orange and oil is 15W40. i'm replacing the starter (ebay) and front driveshaft (Lucky8 stock replacement) since i'll be in there already, but open to suggestions about what else i might need to replace/change. blue or green coolant? would 5W40 Rotella T6 work? i see a small PS leak i'll address eventually. i plan to daily it, and i live in VA. i don't think i'll be doing any serious off roading either and plan to keep it mostly stock, other than switching to terrafirma 16s. Thanks!

 

I think your problem might not be the transmission. That grinding noise you are hearing might be what happens when you shift a rolling transmission in to park. Check to see if transfer case is in neutral. Can you push the car forward or backward by hand? Maybe Move shifter forward and back. If you are sure not in neutral, then Try this. Chock the wheels with big chocks, like tires or something. Have wife start the truck, put it in gear. Lay on ground next to truck so you can see the front and rear driveshafts - NOT UNDER THE TRUCK - NEXT TO IT - DO NOT PUT YOUR BODY IN THE PATH OF THE WHEELS! Now, are the driveshafts spinning? if so, congratulation, you do nto have a bad transmission but rather a bad differential in one of the axles. Rare, but it happens.

If it is indeed the transmission issue and you are going to replace all, suggest you replace the center shaft seal on the transfer case while it is out. I have made a few post about it, do a search. Might also want to consider the upgraded front pump seal for the transmission. Manuals here: https://extinctmotorsports.com/support/

 

Yeah, after we heard the grinding, we checked if the driveshafts were spinning at all. No movement unfortunately so that’s how we got to the conclusion. Is there a gasket between tcase & trans and trans & engine?

 

There is no gasket between the engine and transmission

There is no gasket between the transmission and T-case.

One of the big oil leaks is the seal between the transmission and T-case. If your transmission and T-case have never been separated and you have them out of the vehicle this is a perfect time to replace that seal. There are other seals and gaskets that can be replaced but this one is the main culprit and the other seals and gaskets are more in-depth service. - see multiple YouTube videos rebuilding the T-case.

A good reference video is engine replacement from Atlantic British also on YouTube. Goes through the procedure of removing the engine mounts and lowering the engine for access to the bolts that connect the engine and transmission.

Get a set of bolt extractors just for the cross member bolts. They seem to be made of oatmeal.

Buy new engine mounts.

Buy Extinct's exhaust stud kit and have a tap ready for the old ones. Most likely you will need to remove the exhaust for access to the transmission bolts.

Remove the center console and shifter. You now have the center lock shifter so go ahead and change it while there and you will need access to remove the wiring harness the comes from the top of the engine and connects the rear O2 sensors. Much easier to un-secure the breather lines from up top as well.

Then your big question is when reassembling to you try to make it stock and use all the wiring harness connection brackets in place or just zip tie everything. When putting the transmission back in this will become apparent.

 

The grinding sure sounds like a parking paw not engaging because the TC is in N and the transmission tail shaft is just spinning vs being stopped. I would verify TC isn't in N as mentioned above.