Thread: Engine running but fails to proceed?

Originally Posted by Blknight.aus

cmon JC, I expected better.

try this...

a sprag clutch is a one way clutch. IF you've ever used a pull start to start a lawn mower, chainsaw or whipper snipper then you've aware of what a sprag clutch does for you.

plastic cams were put in to act as a "fuse" just like the panzy pushrod in the clutch assembly in the manual versions of our vehicles costly in the way that if they let go you have to pull the box down but not as expensive as having to replace the whole damn thing before the housing got deformed. Why they couldnt have put in something easier to fix I dont know but you also pick up the bonous of when they start to frag they dont send metal filings to go be disruptive friends with things like your bearings and clutch packs.

auto gear boxes use planetary gear sets to achive their various gears. if there is more than one planetary gear set they are sequenced in some way, Primary secondary and reverse, 1st 2nd 3rd, A B C. there is various ways of actuating the parts of a planetary gear set and in autos its usually done with clutch packs and brake bands. the A clutch pack is a clutch mechanism that acts on the A planetary gearset of an auto. Its just like the clutch in a manual car in the way that it works but its assembley is different, its also a wet clutch. The A pack clutch is usually the most importatnt as it holds the first planetary gear set. If it lets go (depending on the configuration of the box) you either get no drive or reverse gear only.

I knew I could count on you to elaborate and put into more descriptive ways Dave, I'm a bit half baked today A much better description, thanks for that.

I agree about the plastics being a fuse, and not allowing contaminants through to valve body valves and clutches etc but still, a bit silly using them in such a critical component IMHO.

JC

yep but then who'd use something that relies on oil to establish drive.

Originally Posted by justinc

Sounds awfully like a Sprag clutch failure to me Diana. The reverse drive although poor and the ability to get a little forward drive can be the correct symptoms for this type of failure. Some models of the 4HP22 in RR's and D1's had a PLASTIC sprag housing...

JC

Is it possible to drive away normally shifting into 1 when the sprag fails? I recall one of our "departed" members had to take off from every set of lights in "1" due to a failed sprag, but otherwise it could be driven with no ill effect.

not with a total failure no. if the sprag fails theres no way of locking one of the parts of the planetry, From memory (And I dont have the books in front of me) a total sprag failure will let you have reverse and first but it wont shift up what your describing is more symptomatic of a G2 oil pressure problem which can result from a clogged oil gallery, leaking/sticking balance valve or "slipping" of the g2 pump. locking it in first makes it all work by forcing everything to work and once you have some g2 pressure it will generally come good again.

for a work up on whats happening with the theory side of all the bits and pieces that go into the average auto check

http://www.aulro.com/afvb/technical-...nsmission-2tml

If theres something not asked feel free to ask or pm

Had a call from my mechanic this evening, the oil pan came off the auto to reveal lots of metal shavings. Oh well I have worked this box hard and almost 200K is about the life of these I believe so that's what I got.

Diana