Hey Guy's

There is a huge potential for catastrophic clutch failure when using a crawler box.

When using low/low range on down hill decents, the clutch must NEVER be pushed in and the vehical allowed to coast in nuetral!

Wheel speed will back drive the clutch to RPM's far in excess of it failure point. At 109:1 or lower gearing, it is easy to back drive the clutch to failure at 5 MPH or higher speed. My truck will tach out at 4500 RPM at about 2 to 3 MPH in double low- so it's very easy to double that in an uncontrolled decent.

Later

 

Good point, a lot of people don't think about this. People have had clutch disks explode on them while coasting, taking out the bellhousing, floor pan and anything else in the way.

 

Does this apply to auto tranny's also? Or can the marlin only be used with a standard?

 

Yes, the output of the auto tranny will be forced to spin crazy fast. I don't believe it's as much of an issue as with a manual but I can see the possibility of damage occuring. Although... I'm not sure... not a fan of autos anyways so I plead ignorance.

 

Never thought of that problem but it's certainly good to know! I' have 223:1 gearing and I hit 5000 RPM at, oh I don't even know, the speedo didn't move!

 

I would expect that the torque converter could fail in a similar manor-

I've seen what happens when a converter failed on a dragster. It was on Hemi Under Glass w/ a 1400HP 510 cube/in Hemi and a TorqueFlight 727. There was nothing left of the front of the tranny. The pan was gone, the entire bellhousing was gone, and the torque converter was reduced to a 6" disk where it bolted on-

Yes, a crawler box can be used w/ an auto, and would be awesome for wheeling- being able to vary the acsent speed, being able to litterally stop at any point with out having to heel/tow brake and clutch pedals would be sweet! An auto would also further reduce gear ratios due to the torque multiplication of the converter-

later