Does you p38 make a bang-bang-bang-bang noise when accelerating? It sounds like a machine gun. This may be the transfer case drive chain. It stretches out causing the chain to skip over the gears it runs on.
I recently replaced the drive chain on my 2000 p38. Most shops wont touch these and the dealer will charge you big dollars. I got an estimate of 2500 to remove and replace the transfer case with a used one. This was out of my budget. I found an aftermarket drive chain for sale in England for 120 usd +60 shipping to USA http://www.rimmerbros.co.uk/Item--i-STC3238P.
After reading the RAVE and the old post on the same subject as this one I decided to take this on myself. Including taking pictures of what helped me the most and documenting some of the things I wish I would have known beforehand. The only tool I purchased was a transmission jack from harbor freight for 140 dollars. Basic hand tools and a large socket was all that was needed to complete the job. It took me 3 or so hours to remove the T-case and an hour to replace the chain, another 3 to install, so allow about 8 hours to complete the job.
Note: Exhaust and the cross member holding the tranny can stay inplace for the whole job.
First step is removing the rear and front drive shafts, preferably in that order. The front inner joint is tricky. My advice is to remove the front joint at the axle first.
Next is to remove all the wiring and clips from the T-case. There is a banjo bolt on the top of the T-case in the front, don't miss it.
Next remove the drum from the parking brake. Then remove the assembly from the T-case via the 4 bolts. I let it dangle from the cable until re-installation, so I didn't have to remove and readjust the cable.
There are six bolts that hold the T-case on to the transmission. The bottom 4 are easy enough. The top two require some creativity with extensions and u-joints. Position the jack before removing the top two bolts.
Once the bolts are out the T-case will be difficult to remove if their is pressure on the dowels and shaft. It slid right out with little effort when I had it aligned correctly.
Here is a picture of the tools needed to remove the transfer case. Pretty basic stuff. The long extension contraption is what I used to reach the two upper bolts on the transfer case for removal.
Most transmission jacks come with chain to support the load. This is not ideal. Try ratchet straps instead.
The replacement of the chain comes next.
The case has a ton of bolts holding the front and back together. Air tool came in handy here. I used a sharp chisel and big hammer to break them apart.
Take note of the slack in the chain for comparison to the new one.
There is a snap ring on the driven gear. Remove the selector thing and then remove the snap ring and pull both the gears off at once. Easy.
Sliding the chain and gears out.
Put the new chain on, it will be a bit tight when sliding on the splines. I used a rubber mallet to convince it where to go.
New chain shows much less deflection.
Clean and apply RVT to the mating surfaces. Add 2.4 qts of Dexron III ATF.
I hope this convinces some of you to save some money by fixing this yourself. I have more pictures if anyone is interested.
Lessons learned: Power wash the hell out of the undercarriage before beginning so you don't get crud in you eyes every time you rub into something.