Guys,

Puffdragon started a poll that provoked some interesting discussion about the weak points on the 404 transmissions. In order to allow his poll to return to it's intended direction, I thought I'd start a specific discussion about downfalls and possible improvments to the 404 transmissions.

So far we have the sleeve bearings and the 5-6th synchro's as weak points.

It seems like the bearings are burning out from high speeds/loads and the synchro's are failing because the lack of power reauires a great deal of shifting. Synthetics appear to help out but I'd also like to talk about some mechanical improvments.

Increasing power would seem to solve the shifting problem but it would exacerbate the bearing problem.

Some questions:

Are the bearings failing because of a breakdown in the lubrication film?
Do these tranny's have an oil pump?
Are the bearings pressurized?
How is the tranny generating heat when it's cruising in direct drive?

What I'm thinking of is equipping it with a pressure lube system or improving the existing system with an external cooler and synthetic oils.

What do you all think?

(and no personal attacks thank you...) :shaking:

One thing the factory warns against is the use of GL-5 rated lube. GL-5 has additives that attack the 'white-metal' components such as the synchro's. Stick to GL-4 rated lube - I use Redline MTL in my 416 box. I know this is an issue with LOTS of older European cars...

There are also several bolt on heat-conduction 404 trans coolers out there in the Mog world that seem to do a good job of reducing lube temps when driven long distances.

First, the heat is built up because every shaft rotates while your in 6th gear. This of course builds heat.

The bearings so far are a known problem in older trannys. Meaning, that untill some seople fess up, the main failure of the unimog 404 tranny is due to bushing failure has been locallized to trannys that have thousands of unknown miles on them with many unknown flulids .

The obvious fix if chaning to bearings. Which should be a simple thing. The next and maybe a bit easier would be to re design the bushings to handle the heat. New oillite materials etc.

Then you have the tranny coolers and pumps. A simple tranny cooler should make a difference. I also have thought about pressurizing the shaft orofice, whith oil, to force clean cool oil into the bushings first.

But, untill I have a tranny failure, I am not going to look in that direction. I am working on changing the high way gear of the truck first so I can get enough speed to burn up my magical 404 tranny that wont burn up below the max speed of the components. Im thinking 75mph constant is what it will take.