816 wrecker gearbox air valves

[martinsaunders06]

hi guys,i posted a question about airshift operation abit back and since then ive took out/cleaned/refitted the poppet valves in my 816 gearbox and found that the air cyl in transfer now clanks when engaging reverse and then clanks again when returning back to neutral,this i take it the sprag moving back and forth.lookin at the sliging shaft in g/box top which operates the air poppets it is designed to open the forward gear air poppet valve as soon as you bring the gear lever from reverse back to neutral without actually engaging fisrt gear and this also confirmed in how the front prop reacts.the question i have is if i leave the gear lever in the poppet valve venting position the sprag feels like it is in a neutral state- is this correct and if so would it be beneficial to the transmission effeciency to leave it like this by removing poppet valve air supply and connect m35 airshift switch to supply air if reqd offroad. hope anymore is still awake after reading this.thanks martin

 

[jwaller]

it you get the clank in both directions it sounds good to me. thats what mine does.


there is a MWO to put a deuce airshift valve on the 5T but I dont have a copy of it and dont know how the mod is done. wish I have it bc I'd like to do this to my 5T.

 

[martinsaunders06]

i got 2 m35s with airshift in cab but these only have one pipe to transfer sprag(unlike 5t with two pipes to sprag).?does this m35 only have 6 wheel drive going forwards?.seems logical to put a deuce switch in supply line to poppet valves.thanks

 

[jwaller]

the deuce system is totally different. when the deuce locks in it does it via the transfer case with a air shift valve. it does not use a sprag like the 5T trucks do.

 

[timntrucks]

mine makes the noise going into reverse but i dont think it makes it going into forward. and hints as what i should do or check?

 

[martinsaunders06]

had mine apart today and mine does same,when i go into reverse it engages front poppet on g/box which supplys air to transfer cyl which i can here clank and when i pull out of reverse mine dumps air thru vent on valves and then it engages rear most poppet which supplies air to rear most pipe on transfer cyl and i can here it clank again,all this happens without putting into a forward gear.

 

[Cdub]

gota newbie question

......what is a sprag and what is it's main function......???

Thanks,

C'dub

 

[jwaller]

Re: RE: 816 wrecker gearbox air valves

gota newbie question

......what is a sprag and what is it's main function......???

Thanks,

C'dub

sprag is a one way clutch. in this case it's shifted by air such that it locks in the front and rear together. it's supposed to detect a differential speed between the front and rear and when theres a differance it locks them together thus giving you 6wd and not having to flip a switch to make it happen. linda like a very early version of traction control

 

[martinsaunders06]

if the air supply is taken away from valve block on g/box will the sprag unit stay in a "neutral" position and if so would it be safe to drive with it like this? also is there any benefit in doing this?