1990 129 no 5th shift

[Toxicant]

Probably should have put this here rather then SL thread, sorry.

I have a '90 129 that won't shift into 5th gear. I took it to Mercedes and had it checked out and they spent a number of hours on it and came up with a bad HSG mod.

Because I have a repair shop and we're over 2 hours away from the dealer I ordered and installed new HSG with no change. This problem has been going on for a few years now so we reinstalled the original HSG and found a code 9, road tested the car with this controler and there was a 3-5 shift skipping 4th.

While we working on this car in the past, when the new HGS controler was installed we found a bad connection on the trans overload protection switch so I figured the old controler still had that code in it so I cleared the codes in all the mods and road tested.

Back to square one, no 5th gear and no codes in any of the mods. I don't understand why it doesn't set a code when it's not shifting into 5th, Anyone have any ideas?

Thanks,

Ron