old M90 question

[Joe Kamman]

How can you tell when you need to replace the seals and fluid and whatnot? Are there any tests you can do?

Thanks a lot

B

The M90s were intended to go for around 100k miles with no service. And, they seem to be running well below their design limits since it seems like a lot of them are pulled from the junk yards and used without any rebuild.

Given that, the fluid in the drive box is basically a 10 weight synthetic oil. It is very long lived, but will not cost that much to source from either GM (3.8l engines), or Ford (SuperCoupe). Years ago, I was paying less than $10 for a container which would more than fill the cavity to the height that it should be filled.

In terms of seals, they are very high quality Viton® fluoroelastomer seals. Unless the gearbox end is leaking, I wouldn't mess with them.

The other items of importance are the bearings in the drive end. If it feels smooth, they're probably OK. They are fairly inexpensive and easy to put in new ones if you want to rebuild. If you do this, you should probably go ahead and replace the seal(s).

The bearings that the rotors rotate on at the intake side are small needle bearing cups/caps. They are pressed into the casting. I had Magnusun refurbish mine since there was no easy way to get the bearings out. When I got the unit back, I found they had drilled the casting from the rear to get behind the bearing to push it out.

Good Luck