While doing a little researching today I stumbled across something that looks like it could have saved me a lot of time and some money.
Obviously as seen earlier in thread the idler gear in my older (3906) trans was done for and I didn't want to purchase a steel idler from UE since it was $26 shipped. Ended up getting a new 3905 trans for $55 shipped which is supposedly brushless ready and all that jazz. I'm in the middle of changing mounts and what not and not all that pleased with the way it'll be mounted in the chassis. Oh well, give and take right?
Well I noticed that the mounting bolts for the new trans are larger than 3mm so I downloaded the exploded view from traxxas. I can not for the life of me find a view of how the trans mounts to the chassis? There are some 3mm hardware that hold the bottom braces to the chassis that look like they are supposed to go through the chassis into the trans but that won't work since they are 3mm? Any insight?
Ok back to my original reason for posting. What I came across was interesting. I seen this exploded image here.
The part number for the idler gear looked REALLY familiar. Why? Because it's the same exact number without the "X" used in the older 3906 transmission.......
So it turns out traxxas has two different idlers with very similar numbers.
3996X Steel Idler
3996 Plastic Idlers
Do you think it's safe to assume the 3996X will fit in the older 3906 trans? They're $5 new. For that price I'll pick one up and try if my LHS has one.... Looking critically at the drawings it looks like the new idler is wider.