I broke a gearset this weekend.
It left normal. 1.42 60 foot.
On the second gear shift the gearset let go.
My question is.
Do I have to pull the trans and check the sprag like you would have to in a 727????

Thanks for any advice.

Are you feeling lucky? Do you want to hope it is not damaged or do you want to know

I would pull it and for the cost of a pump gasket and tail shaft gasket you would know. Also you get to give the trans a physical if its been a while.

YES!

Even if it still seems fine to drive.

Last one I fixed, the guy was driving it around on the street after busting the rear at the track. I convinced him to pull it and let me look at it, before he took it to the track again. Half the springs were crushed, rollers loose, half were actually still functioning enough to drive the car. It would not have survived the first hit.

In 2017 I broke a ring & pinion at a test & tune before an important double header weekend. Spent Day 1 putting in a new gear and won on Day 2! First pass at a T&T at the next event I went to, the 904 sprag "finished breaking"!

OP did say that it happened on the 1-2 shift. I don't know if that would make any difference, but I wouldn't risk it. .

X2. Friend of mine had same issue. Drove fine. When I disassembled his trans the outer race split the case.

Take it apart and check. At least the drum isn't like a 727 waiting to explode.

Nice thing about a 904, the sprag being out won't put the drum in danger unless you have a real high winding engine (most never get close to critical mass RPM).

In theory, if the 1-2 shift was completed, the sprag should be out of play but ...............

If the roller clutch was under load when the driveline freewheeled, it's hurt. 1-2 shift point would have been up there in the revs.

Thank you guys for all of the input.

Pulling the trans later today and putting in my new spare.

Hopefully back racing this weekend.

please let us know what you find.

Pulled the trans apart yesterday.
Everything checked out fine.
I guess my rear end issue may have been different than a normal ring and pinion break.
It spit the side adjuster out which made the ring disengage from the pinion gear;
so it just freewheeled and did not disengage then engage again like when knocking off teeth.
It just free wheeled like throwing into neutral.
Going to put it back in this weekend.

thanks for the update. glad the transmission was ok, but too bad about the rear.