Just rebuilt my IRS of my 92 4.0 manual and I noticed before I stripped it that the both brake calipers were clogged with an oily sludge, at first I thought the outer seals on the diff had gone, but they're actually good. So this lead me to inspect the rest of the underside. (Unfortunately I am unable to upload a photo for some reason).

There are no fluid leaks from the engine although I can see the power steering has had a few issues and the rack was pretty clogged in oily residue but this this was old and dry. The only wet area is behind the gear box mounting beam so the only fluid pipes I can see are the brake pipe on one side, which I think is the source of some of the leak as the underseal has been stripped of on the underside of the tunnel, so I will replace the pipe. I dont think the fuel pipe is leaking as I cant smell any fuel under there.

The prop shaft is clean, the first heat shield is clogged with oily stuff on its under side but not above. The wet stain is behind the gear box bracket and runs about 12inches towards the back then thins out to thin stream.

So my question is- on a manual what other sources of fluid leaks could I expect to show itself from the tunnel behind the gear box? Do you think the brake pipe is spraying fluid on both edges of the tunnel?

Second question is what do you recommend for cleaning the underside that wont flood my workshop- I dont yet have the IRS in yet.

 

As for cleaning I'd suggest a foaming degreaser and elbow grease. You need to get the underside as clean as possible and then drive it. Then you can see where the leak/leaks originate.