mechohaulic

this is the tool of which i mentioned. wasn't too sure of the switch showed . my day most were on brake pedal valve. another positive moment old school meets new school. is that were the title intermediate school came from

side with magnetic plug really isn't for filling. inside there is a troth which catches oil to bring up foreign objects. that's main reason you had challenge to use as filler hole. opposite side is full open to fill.

defiantly isolate whether the problem is in tractor or trailer first. my day a test light was used ; now it a meter used. there is a tool which plugs in to light cord which will show what works. makes life easier when you sit in cab with light cord check each application. could be broken wire in trailer. do brake lights work on tractor?? not sure of wiring on "new "trucks. is the picture a brake light switch or low air buzzer sender etc. fuses check out ok ???

use caution with the shop air. shop set for 150 lbs , don't want someone getting hurt . those old screw together brake cans might not want that much air after sitting quite for 30 yrs . spray the clevis pins with penetrating oil . just enough air to make things move. trace the copper lines completely if pressures are low. possibly a crushed line restricting air flow. thanks fr updates. side note:: still haven't found LT mack model address

as earlier stated, if this unit is more for show not hauling a trailer or tag along having brakes ; another option (cheap) would be plug feed line to old style TTP (top line) AT THE AIR TANK for appearance it would look good. technically with the right side plugged valve has not been doing anything now except giving unit an air leak.

didn't see anyone mention a magnet , thought possibly this mind was slipping (again) and magnets were no longer there. thanks for the positive reassurance.

if it's getting "an oil change (trans fluid)" did you pull the side plug and check magnet for foreign objects == they still have magnets don't they ???? never did a tipping o=ring repair. darn doesn't that have to almost stand on it's ass/??

old post follow up. I personally would hope for peace throughout the world not only that region. for nothing more then the sake of my grandchildren and their generation.

line left rear (loop) from trolley; line RIGHT REAR from treddle (brake) valve. the Tee fitting front middle line to right covered with autoloom goes to rear axle brake quick release valve ?? line straight out (uncovered) is line going to TTP valve left side ??? if so that's a match and makes sense now . as earlier stated plugged line would go to trailer .

that list tired me out just reading it. yesterday was a wipe out for me. day spent working on DM800 (1/25 scale). it was the day before took it's toll on me. warmer weather : had the power broom and leave blower out cleaning yard. knees let me know -- we are not doing that again. power broom with bristle head on upside down . works well for pulling 3/8 driveway stone off grass.

can't post my pictures; I'm part of the witness protection program. best excuse i could come up with on short notice. LOL😷

just a thought ; if you go through the task of cleaning/ draining trans to remove cover, have a new o-ring and good RTV for reinstall. that's of course high hopes the o-rings aren't on the list of back order parts . down time of unit also a factor. no new oring, leak bad have to repair now ;;then good rtv to the rescue. as always :: clean is the clue.

I do know the location of a guy who attended my auction that bought boxes of my truck stuff. will make a trip and look through what ever he still has. can't get my hopes up ; for an old style TTP valve there, won't know if I don't venture there. mentally it is a challenge : same as driving by my parents home. seeing my old stuff brings in the memories. it sucks when you were/are "married" to your profession.

it's all coming together now. some where in the past the shuttle valve has been discussed. valve has that name based on it's operation. Inside the shuttle ; a5/8 dia +- X 3/4 +- long metal unit having rubber caps slides back and forth capping one port as needed . trolley application the shuttle blocks port going to treddle valve. and vise versa with treddle pedal application. without the shuttle valve air would exhaust out treddle valve when trolley handle applied. the rear frame mounted TTP valve possibly was leaking air because the inside plunger corroded. plugged right side port fed trailer brakes. hopefully slow acting front brake issue is simple as rusted clevis pins or lack of air coming from limiting valve.

a unit such as sanders or other air devise wouldn't (shouldn't) be tied into brake system. the valve first pictured i would go with it being an early TTP valve. air from left side line (brake application) would unseat a diaphram / o-ring equipt plunger to allow air from top constant air to right side plug ( brake cans). another test would be take the 1/4 = 3/8 plug out of right side ; put brakes on check for air out open port. do test twice one with treddle valve other with trolley valve. inside under the removable bottom cover might be a spring : possibly hd tension. new style TTP valves have a hefty spring held in with snap ring. Coffee and doughnut bet the mystery valve in rear not associated to slow front brakes. these are one of many moments I "kick my ass" for not keeping sooo many books (parts included) and tools.

the "some sort of relay valve " could be a standard quick release valve. purpose just as title says. the valve dumps air from brake cans faster to release brakes, other wise air has to travel back to treddle valve to release. if the parts trucks were/ are tractors not straight trucks the shuttle valve may be connected directly on treddle valve if there is one. no trolley in cab no need for a shuttle valve.

I did have a trailer 3-4 weeks ago come in with one wheel smoking opposite wheel same axle hot. cause == the clevis pins were rusted solid to point I had to cut them off with die grinder. this trailer also sat for weeks at a time. possibly your front axle is slow due to rusted hardware ??

front brakes SHOULD NOT be connected to shutttle valve. shuttle valve will have one line from brake peddle valve . one line from cab trolley valve. and third will go to relay valve. air from peddle/trolley should open relay allowing constant air from top to feed plugged port.

with constant air into relay, bottom line from shuttle; i'm going with idea the plugged line went to a trailer protection valve/line. you do have a trolley valve in the cab correct?? does it work ; it must go to rear axle since it may have been for a trailer when unit was a tractor. i would put a gauge on line to front brakes check pressure . possibly the dash control isn't allowing full air to cans.

remember those towel rolls quite well. "knock on wood" maybe that's why i haven't gotten any shots for years , even before covid..

agree on the shuttle valve; but i think that's a different picture/valve then first post ?? like many/most of the topics on here it comes down to :: darn I wish I could be there to see it first-hand.

just not understanding why continual live air for brake system (front) other then going to TTP valve for trailer. as stated, many hands may have been in there. have seen such a cluster recently on a ford tractor /trailer combo. once a road truck; now a farm unit with limited road usage. lights on both units were sooo patched/ spliced. no one knew how to read the sockets for which color went where. there were back feeds, lights going on wrong time etc. goood pair cutting pliers . cut everything out and ran all new.

and from that moment in 1943 the Dam busters came into existence.

can we call you Bob the engineer ; you got us back on track . I sure hope I haven't been a bad influence here with going off topic. LOL 🚂

not defending the counter person; don't think you can call them man/ woman anymore .same as postal clerk no more postman . WTF !! any how I would have thrown the clerk for a loop with " I need something over 450 CCA. it would have put the ball in "her"court. surprised she didn't come out with we don't carry the brand generic!