Hi Folks!

The Jag forum across the pond has a very interesting writeup on installing a drain plug in the transfer case at the bottom of the pinion housing. Here's a link.

Jaguar Forum.co.uk • View topic - Transfer box

The obvious advantage here is you get a much more compete drain of the old oil. The obvious disadvantage is the additional courage to drill a hole into a perfectly good T/C.

However, after reviewing this approach, I'm intrigued. Perhaps one thing I would do differently is to drill and tap for a 1/8" pipe plug with tapered thread. This way, you don't have to rely on a sealing washer, filing a flat surface on the bottom of the housing, or drilling/tapping the hole perfectly perpendicular to that surface.

My primary concern is I don't have any T/C drawings or a scrap T/C to verify for myself the internal clearances necessary for the tapping process.

In this other thread from the same forum, the author installed a drain plug, but with the T/C and output pinion removed from the car.

Jaguar Forum.co.uk • View topic - How to replace a Transfer Box

Has anyone tried this?

Does anyone have a scrap T/C (with output pinion gear) and are you up for drilling a hole to verify clearance?

Does anyone with a disassembled T/C willing to make an engineering judgment of the clearances?

 

Good info

 

I've got a transfer case that's "NFG", so it's a prime candidate for experimental surgery. When time allows I'll drill and tap for a drain plug....then I'll make a report. Cheers, Andy

 

Thanks, Andy!

 

It looks like the UK guys numbers are pretty much correct EXCEPT for the measurement for the drain hole itself. On my 2 TC's, both early, it appears that 47mm would put the hole perilously close to the edge of the pinion gear teeth. There is a 7mm 'window' between the gear and the pinion housing. I measured and drilled at 43mm and there is enough clearance-barely. The small size of my b---s won't allow me to try this underneath a car. What a great idea, but it looks to me that the only safe time to do this mod would be when it's time to replace the TC....that's my plan. I'll try to answer any questions that come up. Cheers, Andy

 

Andy,

I'm having trouble visualizing why you drilled at 43mm and not 47mm.

Is this measurement from the seam between the pinion flange and the case?

It seems to me that the hole needs to be drilled as far back in the "corner" of the pinion housing as possible. Locating the hole 4mm closer to the joint would put it closer to the wider part of the beveled pinion gear, right?

Can you elaborate on the "7mm window"? Is the case thickness 7mm as the guys from UK say?

From the pic of the inside of the housing in the second link above (the pic showing the nasty sludge buildup), it looks like there may be a small pocket on the top of the housing. Is there a similar pocket on the bottom also? Pics of a clean housing would be fantastic. A sketch or better description of the "window" would also be great.

As an experiment, I drilled and tapped a piece of 1/4" aluminum plate with a Q-size drill and 1/8 NPT pipe tap. At proper tap depth, the tip of the tap projected about 7.9 mm through the plate (i.e., inside the housing). This sounds too close for comfort. Perhaps drilling and tapping the T/C after removing the pinion is the only safe way to proceed.

 

Performing this mod with the TC case out is the ONLY way to proceed. I followed the UK guy's instructions verbatim and found all of his measures to be 'spot on' except for the location of the drain hole. 47mm apparantly worked in his situation but NO WAY would I risk it on a functioning TC of the vintage that I have. 43mm was the safe measure. The 7mm 'window' that I am refering to is the distance between the edge of the teeth on the pinion gear and the inside edge of the pinion housing. In essence, I am telling you what worked for me. When you remove your pinion housing you will better understand what I'm talking about. Cheers, Andy