Checking Sprag

-

SBeeMan

FABO Gold Member
FABO Gold Member
Joined
Jan 19, 2013
Messages
209
Reaction score
49
Location
Crossnore NC
I just got my new Dart bracket car ready for it's first test & tune.
Wanted to make a couple of shake down passes off the footbrake before going to the transbrake.
At the first hit,it broke the rear u-joint instantly,it was a 1350 to stock Dana conversion joint.
Is there any way to check the sprag with the tranny in the car?
I spun the tailshaft with a spare input shaft and could not hear or feel anything out of normal.
Thanks
 
Damn good question! I would replace and upgrade regardless. Big mess when they let go!
 
Yeah I've seen the results when they let go,not pretty.
I'm trying to avoid pulling the trans,with my setup I have to pull the motor with the trans:(
 
check the sprag.....the front drum...
could explode...

904 will not
 
So really no way to check the sprag other than taking the trans back down?
I kinda thought that lol
Knowing there are some really smart members on here I just wondered if it could be checked in the car.
 
You want to look for cracks, damaged rollers, if it has a crack the case probably will have a crack. Also see if its a bolt in unit.
 
Yeah chunks aint good lol
I'm gonna drain & pull the pan tomorrow.
 
You want to look for cracks, damaged rollers, if it has a crack the case probably will have a crack. Also see if its a bolt in unit.

If it lets go, you WILL have more than chunks ! There will be nothing usable left , may even tear up ur engine oil pan .
Underside of the car, rear end yoke, etc.
Ask me how I know -----
 
If it lets go, you WILL have more than chunks ! There will be nothing usable left , may even tear up ur engine oil pan .
Underside of the car, rear end yoke, etc.
Ask me how I know -----

Feet, ankles, knees.......more. You know, unreplaceable stuff.
 
Feet, ankles, knees.......more. You know, unreplaceable stuff.
I was lucky, pinned my right foot between the accelerator pedal and the brake pedal, thot I was going to pull a bleeding mess out, but not a drop of blood, nothing broke , did hurt tho . Car was a mess !

thumbnail - Copy (2).jpg
 
No way that I would trust. Do you have a shield or blanket? Blanket here. Already at 75% of normal limb total, don’t need to go to 50%! :):):)
 
Billet front drum in a 727 is a “must” in my book.... gear breakage is a crap shoot. I broke 2 sets of gears (8.75) in my Mirada in the dark ages before I knew such possible mayhem existed.... threw a new pig in and raced. Wasn’t until a friend broke a gear on launch (8.75) locked the sprag, front drum came through the floor. Chuck Lofgren was at the track that day and came over to take a look and schooled us on this phenomenon.... been billet drums and shields/blankets since the early 90’s. Years later my cousin broke a gear at launch (8.75.... interesting pattern here) cocked the sprag so hard it broke the trans case... billet drum stayed in tact.
 
4152283-trans.jpg

Ahhhh the good ole days! .....and he walked away!!
 
Only way to know for sure is to tear it down and look. Cheaper bolt ins can flip the spring retainer thingies too. I’d look if it were me.
 
Only way to know for sure is to tear it down and look. Cheaper bolt ins can flip the spring retainer thingies too. I’d look if it were me.

Yep
Even a bolt in sprag can roll in situations such as axle/ rear end breakage.
Always need to check it in such situations, the stock drum can turn 15k rpm and at such rpm is a ticking time bomb. Billet drum or aluminum drum is good insurance in a 727
 
“, the stock drum can turn 15k rpm and at such rpm is a ticking time bomb”

The drum speed is normally much lower. About 1/2 engine speed when the sprag is functioning. If the sprag breaks or fails, the drum accelerated to 2-3 times engine speed. It explodes normally around 7-8k, or 3500-4K engine rpm.
Best defense is not a bolt in sprag, but the billet drum.
 
Thanks for all the info.
Dropped the pan this afternoon,all looks normal.
It's a fresh rebuild,only run on jack stands & around the pits for warm up. First hit got the u-joint.
I'll be pulling it for a tear down & add a billet drum.
Who's a good source for a billet drum?
 
-
Back
Top