Originally Posted by Mike134
If there is a difference of 3/8" between the 2 axles no way they are square to each other or the trailer coupler. Judging from the Op's comments the front axle is square to the coupler the rear axle is crabbing 3/8" in one direction.
I have no idea of the specs for a TT but you would never find that large of an allowance on an auto.
That will all depend on what the actual toe readings are on the mentioned axle. If one side is toed in and other is toed out but in relation to the centerline of the vehicle the toe angle is equal, there will be no tracking error (if amount of toe in/out is correct. It wasn't until about 1981 that the concept of Thrust Angle Alignment, where all wheels are aligned to the centerline of the vehicle became easy as new instruments were introduced. Before that it was all chalk lines, tape measures, plumb bobs and marks on the floor, not to mention hours of labor.
I spent years explaining and demonstrating this to even old experienced mechanics. Without proper measuring tools (instruments) you can't rely on merely tape measure differences. What's happening where the tire tread rolls on the road is all that matters.