1986 90 - transmission brake

AJofShabby · Mar 30, 2020

Morning all
I am a spannering novice so pls excuse any stupidity. My 90's transmission brake is dreadful. I have been thru the whole process of tightening up the brake drum, releasing some of the tension etc to try to adjust it and I have also tightened the brake cable but without success. Unless anyone has any hints as to what I need to try I will go onto the next step and replace the cable and shoes. The truck has been off road and thru water so that may have affected it.

With time now available I want to replace the brake shoes to see whether that helps. When removing the prop shaft from the brake drum am I best to undo the other end first? And is it sensible ti replace the prop bolts with new? Is there anything else worth changing/greasing/cleaning once the drum is off?

Thanks.
AJ

Wimblowdriver · Mar 30, 2020

When I did mine I found that the shoe adjuster threads were a bit clogged up and when it appeared to be full wound in it wasn't. A bit of backing-off and re-tightening several times (like tapping a thread) got it fully wound in before the final backing off for the adjustment worked for me.

Litch · Mar 30, 2020

You should find that a strip, clean & reassembly will get the brake working like new (assuming shoes & drum are in good condition).

When I stripped the expender assembly on mine I found that it made a massive difference, it had possibly never been touched since new. When doing this, make sure you note how it comes apart so it goes together correctly. The drawings / photos in the workshop manual are very good if my memory serves me right.

kermit_rr · Mar 30, 2020

It could well be full of oil, the back seat does have a tendency to leak and I'll gets into the shoes and drum

tottot · Mar 30, 2020

Just remove prop at the drum end, If the expander looks old/worn replace it. As Litch say's it is important that the pistons in the expander are fitted correct way around or it will not work.

Rougharse Racing · Mar 30, 2020

I had problems with mine when I tightened the cable before adjusting the adjuster at the brake plate. This resulted in there being insufficient reserve movement at the expander, so even though the lever only moved a couple of clicks, it wasn't pulling on the shoes.
Could be worth slackening the handbrake cable right off, then adjusting the adjuster before taking the slack up in the cable.
Mine went from scraping through the MOT to 100% rock solid when I did this.

AJofShabby · Mar 30, 2020

Thanks everyone. A few things to try / be aware of. Happy for more advice ....

AJofShabby · Apr 2, 2020

Hi

Replaced but even the new cable, when pulled up, does not stop the transmission drum turning. I can adjust the drum and it locks, so that appears OK. The cable does not seem to pull on the link to the drum. Any more thoughts? Thanks

nobber · Apr 2, 2020

Got any pics? Pics of the drum end of the cable?

AJofShabby · Apr 2, 2020

Hi

As requested. Not much more detail I can see.

tottot · Apr 2, 2020

The bracket that holds the pivot at the side of the box firmly in position ? We better have a pic of the other end.

dag019 · Apr 3, 2020

That look like it is all set up correctly, however for the amount of effort it is to drop the propshaft I would remove the frum and have a look inside. As a minimum removing and thoroughly cleaning (or just replacing) the expander would be my first port of call. as said above if it is full of mud and grime it may not be functioning properly. It needs to be clean and free to move so that is works.

It is very simple mechanism with central plunger connected to the actuating rod. The plunger is shaped at the inside end into two wedges which small roler bearings between it and the pistons. When you apply the handbrake the plunger is pulled out moving the wedges from the thin end to the thicker end, this is what pushes the piston out against the shoes. If the pistons do not move freely or are the wrong way around, the plunger does not move freely, or the roller is dirty the expander will not function correctly.

To strip it down remove the prop shaft (9/16 spanner) at the hand brake end and tie it up out of the way.
Undo the two retaining screws on the hand brake drum and remove the drum
Lift the top shoe out or the expander and adjuster then remove both shoes (be aware the expander piston and roller may fall out with gravity, you can prevent this by putting an elastic band around the two pistons while you work on removal)
You can now remove the adjuster and the expander for inspection and cleaning
The adjuster is bolted in place, just undo the bolts
Disconnect the hand brake cable from the expander.
The expander is held against the back plate with three metal spring shims. note the order they are in place to allow for re-ffiting

As mentioned above a strip and clean will make a huge difference, it definitely did with mine, and the expander can be bought fairly cheaply as a replacement unit if once stripped down you find it to be badly worn.

Edit: how to guide with picS found on another forum: link

nobber · Apr 3, 2020

AJofShabby said:
Hi

As requested. Not much more detail I can see.

Can you get someone to actuate it while you look from below? Watch your fingers. The idea is to eliminate a problem with the linkage before you go stripping it down.

AJofShabby · Apr 4, 2020

So. Finally decided to remove prop and fit new pads then clean up. Removing prop was a pain. Had to use angle grinder on most of the nuts. Now all off so tomorrow I’ll start on the drum brake. One of the bolts I cut thru was on the handbrake end of the
Prop. Only have shorter bolts For the diff end so ordered new ones for the drum. Not sure how they fit as yet.

nobber · Apr 4, 2020

I cant remember which one, But I am sure one of the props at the Tranny box end the bolts wont come out without a faff. Or it could just be me having a blonde moment.

Huddy84 · Apr 4, 2020

Definitely clean out the expander. Mine was struggling, gave it a good flush out with brake cleaner & oil and it’s rock solid like new now.

When off-roading, especially wading, grit and dirt get into the mechanism and jam it up.

dag019 · Apr 4, 2020

AJofShabby said:
So. Finally decided to remove prop and fit new pads then clean up. Removing prop was a pain. Had to use angle grinder on most of the nuts. Now all off so tomorrow I’ll start on the drum brake. One of the bolts I cut thru was on the handbrake end of the
Prop. Only have shorter bolts For the diff end so ordered new ones for the drum. Not sure how they fit as yet.

From memory to refit the bolts you need to remove the drive flange from the transfer box. It is not too difficult you just need to undo the large nut seen in the centre of the handbrake drum and the drive flange will slide off.

jamesmartin · Apr 4, 2020

you need a set of external circlip pliers too

steve2286w · Apr 4, 2020

Ensure the wedgey pistons are installed correctly it’s possible to get the taper the wrong way round as I did

So when handbrake pulled no movement on shoes

AJofShabby · Apr 5, 2020

Blimey. What a faff. So, drum off. Pictures attached. I think it is fair to say that water has been involved.

The top piston on the adjuster was wedged tight and you could not turn the piston at all. A large screwdriver and lots of penetrating oil fixed that. Now clean. The expander doesn't move when the handbrake is pulled on. I will clean/replace accordingly.

Thanks for the advice so far.

1986 90 - transmission brake

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