The Internet is full of people describing the affliction you describe. Apparently it is (or was) an issue.

Being aware of that I took special precaution when I bought an Athearn Genesis SD70MAC Spirit of Cumberland two years ago from Pacific Western Rail Systems. I have a blog entry about it.

Are the bearings on the inside of the wheels or outside in the truck frame? Could be one of the holes the axle rides in is out of alignment if it's an out side bearing. The truck frame could be also be twisted.

Kind of hard diagnose without actually seeing it. How about some pics if possible?

Bernd

This information is not from personal experience, But from what I have read this is a manufacturing defect. It is an alignment problem and the best fix is to contact Athearn for replacement parts.

It seems The outside bearing assembly is not built with the proper alignment. All the wheels are not contacting the rails. Athearn is aware of the problem and has taken corrective action. New parts may be available by now.

Good Luck

John

**********************************************************************************************************************************************

Untutored courage is useless in the face of educated bullets. >> Gen George S. Patton

Which SD70 are we talking about?  Is it the older run of SD70's or the newer SD70Ace's and SD70M-2's?

I have noticed a few problems on the front truck of my SD70Ace.  Haven't had the chance to really look at but all my other 6 axle power runs fine.  Even the older run athearn sd70's!

Dustin,

I'm not sure what production run had the problem, and it is possible that I addressed the wrong problem. The information came off of the internet, but i don't remember the site.

Checking the wheel contact on glass or a solid surface would reveal if the truck has this problem

It is possible that Atlas fixed the problem and the overseas factory reintroduced the problem. 

I am guessing now, I do not know, so I shall shut up.

Regards,

John

**********************************************************************************************************************************************

I not only use all the brains that I have, but all that I can borrow. >> Woodrow Wilson

It is not just the SD70, Their 6 axle trucks seem to have this issue. It is the brass side wiper that the axles fit into. They are very slightly warped vertically, hence no contact on one of the leading or trailing axles. Simply take them out and bend them back by hand using a very flat surface, such as glass to verify they are flat. In one of my locos (the SD70 I think, was off by over a 1/16" !!)  Caused tracking problem on curves and switches. Simple fix, good luck. 

Steve

I ran my Genesis 70Ace today and it looks like my problem is on the front wheel of the front truck.  It does seem that the wheel is making contact with the rail but it seems that it has "light" contact with the rail.  If that makes any sense!  But here is the thing....it only gives problems when the engine is turned around Trailing.  Runs fine when the unit is leading.  And as mentioned above, the issue is on some curves and switches, but is very sporadic.  

I run this unit with another genesis SD70 and that unit runs fine as does all of my other 6 axle power.  Does this sound like the same problem as mentioned above or is it something different?

When they fabricated the truck, it was pulled out of the mold too quick and it "warped". BELIEVE ME, send it back to Athearn and they will fix it for no charge. I had the BNSF Vomit Comet, and it was BAD. Every time it transitioned through a switch, it would derail. Now it's good as new!!!

Again, it may be the truck, but there is enough play in the brass clip that all it takes is a very, very slight bend downwards to even the pressure on all three axles.  I may go as far as suggesting to over bend so that there is more contact pressure on the two outside axles, similar situation to a flangeless driver on huge steamers.

Steve

The fact that this problem persists, based on the posts in this thread concerning new SD70ACe, is incredible. Especially within the context the manufacturer has replacement parts for previous runs.

I ended up selling my 2 SD75Is for pennies on the dollar to a person who wanted only the motors. As good as the new Athearn units look, I confine my purchases of this locomotive to Kato only.