First off, I know my tranny is on it's way out and I will be rebuilding it very soon. I have all soft parts ordered, but I'm trying to get a handle on what hard parts I may need based on symptoms. One of the bad things the tranny is doing now is slipping in first gear (Drive) when accelerating from a stop. While the tranny is slipping, if I drop it down into first gear (Manual), it instantly stops slipping and acclerates normally. In first gear (Drive), the overrunning clutch (sprag) holds the rear drum stationary and in first gear (Manual) the rear band is applied to hold the rear drum stationary. Based on what I described above, it seems to me that the overrunning clutch is not holding the rear drum like it should in drive and when I select 1st manually, the drum is then held by the band.

OK, here's my question. When the overrunning clutch fails or slips (like I believe mine to be doing) does it usually take out the clutch race as well? Since the clutch race is pressed onto the rear drum and then machined, the rear drum/clutch race has to be replaced as an assembly. Of course, the clutch I can get for around $12, but a new drum/clutch race assembly is about $60.

 

I have the service manual in front of me with the flow chart but cant seem to copy it to the post. I'll keep trying.

Ok no luck try Here On the left is links to the downloadable 3rd gen service manuals. Under section 21, there is usually a flow chart/troubleshooting chart that tells when each part is applied during which tranny operation. Shuold help in diagnosing tranny troubles.

 

No need to post it on my account.... I have several manuals. I just need to know if the clutch race (and hence the rear drum) typically needs to be replaced when the low overrunning clutch (low sprag) fails. My local tranny shop has the parts sitting on the shelf if I need them.... I'm just trying get a handle on addtional costs I may incurr.

 

Oh ok then. Sorry! my bad!! Well then that I cant tell ya...

Ok reread the the post, your right on the overrunning clutch problems. Let me know what you find. I'm looking aat pics now that might help shed some light on this.

From the FSM: Which I imagine you already know......but:

Do not remove the clutch race from the low-reverse drum under any circumstances. Replace the drum and race as an assembly if either componenet is damaged

I guess in your case it would depend on how bad it failed. If the race is bad then I would say so. According to this it seems the race must be a press fit onto the rear drum. Hopefully a more knowledgeable tranny guru shows up. Sorry i cant help any further

 

Yeah, it's pressed on then machined. At this point I'm just going to assume that I need to replace those parts. Then if I don't.... it'll be a pleasant surprise.

 

Outer Overrunning Clutch Cam In Pressed Into The Case. Rollers And Spring S In The Clutch Itself Just Sets In The Outer Cam And Can Be Removed With Your Fingers. The Inner Race Is One-piece Of The Rear L/r Drum. The Problem Is, Which I Hope Is Not The Case Of Yours, Either The L/r Drum Broke, Which Pray To God It Is Or The Rollers And Springs Wadded Up And Turned Sideways Because The Nylon Holder Melted And The Outer Cam Broke Out Of The Trans Case And Cracked The Case. If The Latter Is Your Problem, Then You Will Need A Case Or Sometimes Can Be Fixed With A Bolt In Overrunning Clutch Outer Cam.
Dhawk

 

I know in 727's that the O/R clutch cam is a press in unit and bolt in units are available. According to the manuals I have (FSM and ATSG) the 47RE (A618) tranny uses a bolt in O/R clutch cam. The bolts go through the OD piston retainer, through the case and into the O/R clutch cam and serves to attach the OD piston retainer to the case as well as secure the O/R clutch cam from spinning in the case.

The A618 is based off the 727's design but several parts in the rear of the case had to be altered to accomodate the OD unit that is bolted to the rear of the case. From the ATSG Manual for A500, A518 & A618:

Note the clutch cam actually has 12 holes in it.... 11 threaded holes for bolts and one unthreaded hole.

Based on this.... it sounds to me like you're mixing a little 727 tech into the 47RE.

 

Mixng the 727 and the newer trannies, is what makes these trannies rock of course with a little fine tuning.