The RT Differntial Mount

For the differential, Nissan used a rubber mount bolted underneath and a flexible strap across the top. The strap was supposed to limit any upward movement without transmitting vibration or noise to the interior. It was cheap and worked OK, but Ron Tyler came up with a better version.

Commonly known as the RT Mount, it bolts into the same holes as the strap (which gets thrown away) and has a polyurethane "bumper" to limit differential movement. It's very well made, but it doesn't fit the early cars.

As it turns out, the transmissions for a '70 and '71 240z were mounted slightly back than with subsequent years. As a result, the polyurethane bumper makes contact with the flange that connects to the driveshaft. Above the bracket, the nut holding the bumper makes contact with the parking brake mechanism. Not good.

Unless I was willing to go back to the strap, I'd have to modify the RT mount or build a new one from scratch. I decided to modify the mount and here's how I did it.

I took off the polyurethane bumper, and with some corrugated cardboard and hot glue I made a mockup for a bracket that would move the bumper rearward and clear the parking brake mechanism. It took a couple of tries, but cardboard and glue are pretty cheap.

Not the prettiest thing I've fabbed, but it's rugged (12ga steel) and that's what counts.

Here's the finished product. Sure, the yellow paint is goofy but it makes me laugh.

The bumper is centered perfectly over the differential case and I trimmed it back to leave a gap of about 1/8" between them. The nut holding the bumper no longer interferes with the parking brake cables.

It took longer to make than I'd hoped, but that's something which happens frequently with a 47-year-old car.