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View Full Version : Hand Brake Failure - what should I be looking for?



CRiordan01
05-11-2017, 10:10 AM
Oh wise ones! I need help identifying a component failure...

I have a 1974 Series III that partially rolled on me this past December. A lot of other things going on between now and then, so I'm only just getting a chance to tackle the underlying issue and I need some guidance about what to focus on replacing.

As background, I had parked my SWB at the top of a hill to open a locked gate and then cut several errant branches that were encroaching on the dirt road leading down the hill. I left the vehicle running but had set the parking brake; it was parked on a very slight decline and there was no indication of movement when I got out of the vehicle. I was only out of the vehicle approximately 3 minutes...long enough to open the gate and descend approximately 60 feet to cut several stray branches...I heard a noise as I was throwing the last branch off-trail and saw the vehicle rolling at me doing around 15-20 mph. I managed to get out of the way, but the truck ran about another 100 feet farther down the trail before catching a rut, bouncing off its right side (it actually bounced back upright), and then hitting an earthen embankment on the opposite side of the trail that finally stopped it. To its credit, the engine never stopped running, and was driveable although it had significant body damage to the right side body panels and front bumper. A "sh*t you" moment, if you will, when you briefly think about trying to jump in the truck and then realize the idiocy of the notion.

Clearly, the hand brake did not hold the vehicle. I have kept it parked in gear and with wheel chocks since the accident, but I need to make sure this doesn't happen again. To that end, what components in the transmission brake would be the likely culprits?

I'd like to do a focused parts replacement versus a blind wholesale replacement of components if possible.


And am I off my rocker to believe that a transmission brake, in good order, should be able to hold one of these vehicles stationary even on a slope?

Any input is appreciated.

Cheers.

Corey

slowmo
05-11-2017, 12:20 PM
It might just need to be adjusted. Look on the back side for the square adjuster.

If not it is basically a drum brake with shoes. Not complicated at all.

CRiordan01
05-11-2017, 12:43 PM
David,

Thank you for the response. I have records from the previous owner that indicate he had the transmission brake replaced, so hopefully that is all it needs. I did not realize it had an adjustment.

leafsprung
05-11-2017, 02:40 PM
Make sure the adjuster and expander are working properly - make sure the linings are in good shape (not soaked in oil) - if they are oily replace output seal and check the output flange for scoring. Make sure the ratchet pawl is sharp and engaging the teeth in the ratchet and the the spring is strong that forces the pawl into the ratchet teeth. Make sure the bellcrank pivot is well lubed and that all the clevis pins are securely seated

-Ike


David,

Thank you for the response. I have records from the previous owner that indicate he had the transmission brake replaced, so hopefully that is all it needs. I did not realize it had an adjustment.

lumpydog
05-11-2017, 02:42 PM
You can adjust from two places. One is a sort of gross adjustment. The other is more of a fine adjustment.

The gross adjustment is made using the nuts on the rod pictured here (https://goo.gl/photos/6svP1Xiou9xeJzgw9) - item 29. That will adjust the point at which the handbrake engages the transmission brake.

The fine adjustment is described by Slo - it's a square adjuster on the driver side (front facing) of the transmission brake drum. Clockwise will fine adjust the brake pad's at-rest proximity to the drum. I believe the workshop manual describes (with the hand brake released/off) tightening the adjuster all the way and then backing it off "two clicks" as there is a spring designed to make a click noise. You can feel the clicks too as the adjuster gets easy and then gives resistance.

Bottom line - if the rod is too loose, even with the hand brake all the way on, the brake may not engage. Make sure the rod allows the transmission brake to firmly engage and the brake handle does not reach the top of its travel limit before it can engage the brake - then make sure the fine tune is set per the manual.

Take it for a test drive. Get out and feel the drum. Is it hot? Fine adjust is too tight. Back it off a click and test again. You should be able to pull the transmission brake lever up 3/4 of the way and have a firmly engaged brake.

If I were you, I'd go one step further and pull the drum off to make sure there is no oil contamination in the drum or on the shoes. Very easy to check for.

[Edit - cross responded with Ike - sorry for some of the repeated advice]

CRiordan01
05-11-2017, 02:50 PM
Thanks for the additional responses! Lumpydog in your post you referenced a picture but I did not see one with your post...am I missing the pic or did you forget to include the pic / link?

Bodywork is being corrected now, so when I get it back, I will start working on getting this all sorted out.

CRiordan01
05-11-2017, 02:50 PM
Lumpydog - disregard my comment. I just saw the link.

lumpydog
05-11-2017, 02:51 PM
Thanks for the additional responses! Lumpydog in your post you referenced a picture but I did not see one with your post...am I missing the pic or did you forget to include the pic / link?

Bodywork is being corrected now, so when I get it back, I will start working on getting this all sorted out.

Added link. I'm over my attachment quota on this forum. No idea how to resolve that so I needed to go load the picture elsewhere