Spun sprag race!?

gman99

gman99

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Joined
Sep 27, 2012
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So how many of you guys have spun a sprag race? I kinda figured it was a weird freak failure until I took the core transmission that I had laying around and pulled it down. I went through and inspected all the parts and lo and behold the sprag race was loose inside that case as well.

Anybody else have experience with this?

IMAG2029_zpsq5clbpsu.jpg
 
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So MVB folks should be safer.
I was thinking backwards for some reason and thought being in D would prevent it for some reason.
 
The core 47re case I have has a loose sprag race also. I drilled and pinned the race in 3 places. As well as re-staked the race from the top. I know its not as good as a bolt in sprag race put it would take some serious force to budge that thing now.

I was just looking for some input on how common this failure is. If I would have thought it was an issue I would have pinned the sprag on my original build.

Here's what I did on the "new" case.

IMAG2032_zps9vfxoqgo.jpg


I did stake the pins in place after the photo just to clarify...
 
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It's fairly common, I've done it a couple of times unfortunately. Once even with it bolted.
 
hopefully those pins work.

If people have messed up bolt in sprags, I'm not going to spend $100 on something that MIGHT work.


Also, if you drop from OD or third to neutral after a hard run, is this what grenades or is this what allows something else to speed up and fly to pieces?
 
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Yeah I was pulling my boat when it finally let go. The tranny had been having weird hiccups for a week. I had just put in a new gov solenoid and transducer. I went to pull into a restaurant from highway 17 and it started popping and banging and I almost didn't make it into the parking lot. It would have been a heck of a mess if I had gotten stuck crossing traffic that's for sure.

I thought it was the input or a planetary coming apart. Wish I would have gotten a picture of me putting the truck on the back of my flatbed wrecker. It did not look safe up there at all:hehe:
 
Highwayman said:
hopefully those pins work.

If people have messed up bolt in sprags, I'm not going to spend $100 on something that MIGHT work.


Also, if you drop from OD or third to neutral after a hard run, is this what grenades or is this what allows something else to speed up and fly to pieces?
Click to expand...


It happens when you put an absurb amount of torque on the sprag, the overrunning clutch is "held" into position, so it is trying to spin the sprag, and the sprag just starts to spin or even break.
 
zstroken said:
Lots of torque. They make a bolt in sprag to use. A preventative measure is to use manual 1
Click to expand...

Interesting, maybe this is why I've never had problems with any stock sprags, has worried me sometimes tho. I usually launch my 8000lb pig over 40psi:hehe: but i have a MVB
 
12vCumminsFTW said:
Interesting, maybe this is why I've never had problems with any stock sprags, has worried me sometimes tho. I usually launch my 8000lb pig over 40psi:hehe: but i have a MVB
Click to expand...

I believe launching is a shaft strength factor. I believe 3rd to od locked can put alot of stress on the sprag though. I do use manual first almost every time I launch it hard off the line.
 
gman99 said:
I believe launching is a shaft strength factor. I believe 3rd to od locked can put alot of stress on the sprag though. I do use manual first almost every time I launch it hard off the line.
Click to expand...

1st gear loads the sprag hard, because of the gear reduction in the transmission.

Whatever torque the engine makes, multiply it by 2.45.
 
damn 1400ftlbs x2.45= a mangled pile of aluminum! How the hell do these trannies survive??
 
Ive had these trannys apart quite a few times but i honestly dont understand how manual 1st isnt as hard on it? lol
 
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