833 OD sticking in 4th, chipped synchro

[dhowlan]

I have an 833od behind a slant six (out of a feather duster originally) that I rebuilt a little over 10 years ago. Recently, it got stuck in 4th gear. Disconcerting when it happens. After several attempts on the freeway offramp, it came out. I thought it must be a shifter rod coming loose as I've had the nuts back out before, but all was in place and it would stick in 4th even with all the rods removed. Bonus, ti got more and more difficult to get out the more I messed with it. The last time required starting the engine and letting out the clutch before it slid out.

To cut to the chase, I have spent 3 months with gears 1-3 working fine and me avoiding 4th. I finally had time to remove the transmission this week. After removing the side cover and much staring at it in various gears, the issue is that a single strut key is catching on it's synchronizer ring. If I push that key down, it will slide out of 4th. The synchro ring is chipped on top on the key side and the key is catching on a step in the synchro on the key side. Hopefully the photo will make that more clear. So the key tips up slightly when shift into 4th, then it can't come back down to flat because it hits the step in the ring.

So I know what the problem is, but I don't know what caused it. I realize I am destined to disassemble it to at least replace that ring, but I would really like to stop it from happening in the future if that's possible. Any ideas or suggestions are much appreciated. Anything I can measure to confirm things are where they should be while it's still assembled?

 

[AJ/FormS]

I can tell you exactly why that is happening. The slider is over-shifting.
And this happens when one or more of the following conditions exist;
1) the brass ring is sitting too far down on the brake-cone, or
2) one of the energizer springs is either broken or out of index, or
3) The input gear is too far towards the engine, or
4) the mainshaft is too far toward the rear end
5) the shift interlock levers are worn, or
6) the wrong slider has been installed, or
7) the wrong style brass ring has been installed
8) the cover is not properly located

Ima going with numbers 7 and 1, because
that ring does NOT match the slider-hub. The brass is a pre-72 type while the hub is a 72-up style
Take a look at the other brass and MAYBE you can see what I mean.
Edit; I added #8

 

[dhowlan]

Thanks for replying. I would like to go through these one by one so I'm clear.

1) I read you said at least .050 clearance and there is at least that. The part of this that concerns me is that this brass ring has more space to move laterally than the others.
2) By feel, each key is supported by a spring as it springs back when depressed
3) I'm not sure how to confirm that. The bearing is flush with the case and the mainshaft gears align with the countershaft gears
4) Same as above, but at the rear
5) there is little wear on that 3/4 lever. In fact, in the 4th gear direction, it isn't even shiny. The scissor slots in the "comb" do not appear worn.
6) slider is original to the transmission, afaik
7) all brass rings were replaced when I rebuilt it. The rings were provided by Brewers. If one is incorrect, they all are. It's been a long while, but I doubt I would replace an item without confirming it was the same as the worn item.

I'm confused by what you said on the brass ring. Isn't the ring that's in there the later type? from Brewers site: '70-up stop ring syncro assembly

 

[AJ/FormS]

The ring that matches that hub/strut configuration has a different wider "key" that more closely matches the strut width.
The ring that I see there has the narrow "key" that matches the narrow struts of the older design. If all your brass is like that, and the 1-2 slider hub has the same wide struts as the 3-4, then they would all be wrong. I find it hard to believe that it would shift properly, assembled that way.
The lateral movement you mention, has to be less than the distance between two adjacent clutch teeth

OOPSY no you got the right brass in there, my memory ain't what it used to be

so you can ignore this post, all of it.

 

[dhowlan]

I thought there were 2 types brass ring options and the one on the left is the later version. ???

 

[AJ/FormS]

And that just leaves #1

If you have the matching later style cover with the scissor-type interlock, that style cannot be over-shifted at the cover. But the overshift occurs on the adjacent gear when the brass on it sits too low on the cone.
So then on an overdrive A833, when you shift into Direct gear, the slider only can go so far. but the brass can flop around between the cone and the struts. The only thing that holds he struts in place is the energizer springs. So if they are weak, the struts can move too far towards the Input gear, and then the back ends pop out. Once out, they don't like to pop back in by themselves, so now you are stuck in Direct gear.
The proper solution to this is a triple whammy.
1) install a brass that sits higher on the cone, and
2) pop the energizer springs out, and stretch them out a bit to put more pressure on the struts, and reinstall with the ends offset from the other side, and
3) move the input gear as far back as is possible. This starts with the big snapring on the bearing. The one that comes on the bearing from new, is the wrong one. You gotta use the factory original one. They are different thicknesses, and if you install the fat one, with just one gasket, the retainer usually gets broken during the install. But worse is that the fat boy pulls the input gear forward out of the trans by the difference in the thicknesses.
Next is the smaller snapring, which are select fit. By the book, you have to drive the bearing as far back as it goes then install the fattest ring that fits. I find it helpful, to instead, install the thinnest snapring, drive the bearing into it, then measure/install shims between the input gear face and the backside of the bearing, which will move the input towards the slider hub, which will stop the brass from moving too far forward, which will keep the struts inside the slider, which will prevent the back-ends from popping up and getting stuck, which will prevent the slider from retracting, which, when it happens almost always leaves you stuck in direct.

BTW,
when you manually move the slider into direct and slam it into the clutch teeth, that slider is always too far forward. The cover, in good shape, NEVER shifts it that far....... unless someone installed all the wrong bolts in it. As to cover bolts; All but the bottom two have shoulders on them. And two of the shouldered bolts go in specific locations that are deeper in the trans case to receive the shoulders. This positively locates the cover, which positively locates the fork, and thus, the slider........... unless the fork is worn.
The fork only wears when you have to hold the trans in gear because it wants to pop out, usually on deceleration. When that happens, you gotta fix the clutch-teeth and the fork, and the slider points AND most importantly, back cut the offending teeth.
In the pic you provided, I assume the gear we are looking at is the overdrive gear. The clutch teeth on it are pretty banged up, which I don't often see on the overdrive-gear. If it was mine, I would re-point them and the slider. And any other gears that look like that. That rarely happens to an overdrive gear, because the speed-match is pretty small at 60/65mph, and nobody speedshifts into it. Usually, those teeth are pristine. But in your case with a slanty, it's not a big deal to leave them like that.

 

[AJ/FormS]

I thought there were 2 types brass ring options and the one on the left is the later version. ???

yes, I effed up

 

[Inertia]

I've had a similar condition when I didn't get the rear snap-ring into the tail shaft groove, allowing the tail shaft to move forward and jamb the brass between the input/output shaft .

 

[AJ/FormS]

When I rebuild an A833, with good used brass;
I grab the gear with the least-worn brake-cone, and fit every brass to it. I select the highest-sitting ring and install it on the input gear, for this very reason, namely to prevent overshift..
The next highest goes to the hardest-working gear, usually second
The lowest sitting ring goes on First, cuz it works the least hard, unless the driver is known to downshift hard into it, then the lowest goes to Third.

In this way, I get 100,000 miles out of a set, or more. Except maybe Second.Yes, I have, been driving A833s since 1970, lol. I wore out a lot of Second-gear brass. The last time I pulled mine out, I set a new personal best time of 17 minutes. And I coulddabin faster, cuz I wasn't actually "racing", and the time includes unbolting the GVod, and the front section of the 3" dual exhaust. But I must admit, I used a 4-post lift.lol. and my unit is all alloy so weighs about 85 pounds so no jack was required.
BTW-1
when installing "new" brass rings, you gotta check every one of them as to concentricity with the cones. I have had quite a few come to me that were oval, and when installed like that, it creates shifting problems. Yes, they can be straightened, I used to do it all the time. Oval rings sit too high and rock on the cones.
BTW-2
The back bearings on some A833s is specific to it. The off-the-shelf bearing does not fill the receiving cavity in the tail because it is too narrow. and by quite a bit. This allows the mainshaft to move backwards towards the rear end, and all hell breaks loose, lol.. IIRC, this is in the B/E tails with the bigger 308type bearings.

 

[dhowlan]

That's actually 3rd or direct drive gear in the photo.

I have zero memory of whether the snap ring in the front is new or factory. I will be mindful of that when it comes apart and goes back together.

 

[AJ/FormS]

Of course it is, lol, they almost always stick in the direct position, lol. IDK what I was thinking...... but the rest of he story remains, except
You have probably overshifted the slider into od, and popped the struts out on purpose, right? The cover levers should NEVER be able to shift it that far. And to tell the truth that picture looks wonkey. Almost like the front snapring is out of place and the slider hub has walked too far forward, or the slider is too narrow. Boy I'd really like to see a pic with the slider in fill view and shifted into direct, so I can see the relationship of the hub to the O/D gear..
BTW
You don't gave to take the trans apart to get the struts back in place. I have done that job, laying in the street, of a far away city.
Just put some pressure on the slider towards Neurtral, and with a small screwdriver, pop the struts back in, keeping the pressure on, until the slider pops into neutral.

 

[dhowlan]

Direct drive photo. And no, I didn't pop the struts on purpose. In fact, before removing the cover I tried very hard to shift into 4th and then not move the lever so I could see where it was ending up from the lever motion. The previous photo is not from that attempt, but it's hard to get the sleeve to sit anywhere else than in that position. I'm still having a hard time understanding what stops the slider outside of the lever and detent.

 

[446acuda]

Besides the A833, there is another application that uses a special 308 bearing with a 307 bearing inside diameter. The "7" in 307 means 7 x 5 =35 millimeter inside diameter but the special 308 has a 35 millimeter outside diameter when it should have a 40 (8 x 5) millimeter inside diameter.
Back on topic, there is a 0.795" wide 308 bearing that would fit an A833 but the bearing should be the 0.825" wide version usually called the 308 SG8.
It may be that you have 1 or 2 incorrect bearings in the transmission, moving the input too far forward and/or the other mainshaft gears too far rearward, and it may have taken years to wear just enough for the problem to appear.

 

[446acuda]

Here is a picture of a 308 SG8 and a 308 LOE. The snap ring groove is in the same position relative to one side of the bearing but is 0.030" shorter on the other side which would move the input forward.
Disregard my comment about 2 incorrect bearings--it can only be the front bearing since the rear would be a 307 in an a body transmission, not to mention that the wrong rear bearing in a 308 tailshaft housing (B/E/truck) would prevent the bearing from being seated or keep the snap ring from seating in the groove, depending on the situation. If the bearing is seated the snap ring will not seat, if the snap ring is seated in the bearing the bearing will not be seated in the tailshaft housing. This applies to incorrect 308 LOE bearing in 308 bearing tailshaft housings like used in B/E/trucks/vans. In other words, the incorrect 308 bearing is easier to spot when installed in a tailshaft housing.

 

[AJ/FormS]

Yeah what He said^^; and thanks to @446acuda, for that update.

Now, to the OP, Thanks for the new picture, which shows that the mainshaft appears to be in the correct position. So then, If the slider was in the position shown, with the cover installed, then it most definitely is over-shifted. With the late style cover with the scissor interlock, this is not supposed to be possible.
So then, what I would do is;
Firstly; examine the 3-4 fork, and make sure that it is not bent. The centerline of the pin should be on the same centerline as the fork-arms. If you are able to, put the pads of the forks onto some kind of surface and make sure the pads are parallel, and that they fully contact your test surface, simultaneously. If the fork is bent, it will usually show up as pads that are worn unevenly. Obviously, if the fork is bent, throw it away.
> But if the fork passes;
>Level the box front to back, cover side up.
>Work the struts back into the slider and put both of the sliders into Neutral. You may notice that in Neutral, the 3-4 slider may move back and forth a lil. see Note-1
>Pull the 1-2 fork out of the box. Install only the 3-4 fork.
>Install the cover with the two extra-long-shouldered bolts in the correct locations, finger tight.
>Shift the box into direct, and spin her over a few revolutions; then remove the aligning bolts and lift the cover straight up, fork and all.
> if the slider did stay where it's supposed to be, lets get a pic of where it is . If it is in the correct location, then we gotta figure out how it ended up being over-shifted.

Note-1
The struts are supposed to pop up into channels in the slider, and minimize that, but the fork will center it. If the strut springs are too slack, you can only change that after a teardown. I stretch the crap out of mine before I install them.Because, it is the dtruts that push the brass onto the brake cones to slow them down, and they only have a few milliseconds to do it during the typical shift. If the slider moves over them too fast, the clutch teeth will clash and tear off the points. Eventually, shifting becomes difficlult as the teeth brass stops working. Look at the teeth on your overdrive gear; they have already been butting for a long time. The point is this; stretching the energizer sprinds will make the shift effort slightly higher. But your struts will finally be able to their job. Just stretch them!.
BTW, if you are running a synthetic trans fluid, good luck with that. Thatstuff is so slippery, it takes forever for the brass to reach synchronization. Couple that with weak energizer springs and gear clash is the natural result. I run 50/50 DextronII and 85/90EP oil. The EP oil helps protect the cluster pin, and that's the only reason I run any at all.

 

[AJ/FormS]

BTW
there are TWO Mopar short-tail A833od boxes.
The slanty has the smaller M/S that uses a 307 bearing and a 904-sized driveshaft yoke.
The everything else box, has the bigger M/S that uses the 727-sized driveshaft yoke, but I just cannot remember about the bearing; it's been over 20 years since I messed with those.

 

[dhowlan]

Thanks to you both. It's been so long since I rebuilt it (pre me digitally recording everything) I don't have a picture of what bearing is in the front. I dug out the receipt and the rings are wt307-14 quantity of 4. Unfortunately, the bearings were listed as RBK (rebuild kit) without any specifics on what bearing is in there. Again, I'll look to see when i take it apart. That will probably start tomorrow. I will experiment with lifting the cover in direct drive without the 1-2. I hadn't thought to do that. duh.

The 3-4 fork is not bent. It's a really good clue, I think, that there is a little wear on the outside (direct drive position) but no shine at all on the inside. It's like the slider wants to go inboard on that shift.

 

[AJ/FormS]

It's like the slider wants to go inboard on that shift.

Or like the od gear is trying to kick it out.
Or possibly before the last rebuild it was in the other way .....
no matter, if it ain't obviously worn, she's good to go.
----------------------------------
BTWs (chit-chat)
> when the forks do get worn, you can bet it's because the gear is trying to push the slider into Neutral. You gotta fix that asap. The clutch teeth are easy to back-cut at a small angle with a Dremel-type die grinder, the slider is a bit more difficult. But since I bought my first synchronizer assy back in about '72 I've been fixing them no problem. As for worn forks, I just stick some hard brass on there. I don't replace forks unless they are broken, and I have not yet broken a steel one,
>I like the old style cover better, but the new-style brass better, as they don't break for me: as to forks no opinion.
>I'm gonna guess that most shifting problems start with a loose external shift levers and/or loose adapter plate. I loc-tite the cavities between the levers and the studs, and loc-tite the nuts. But you gotta Not get loc-tite between the studs and the cover, lol, cuz then it wont shift at all ......
> yeah, I loc-tite the adapter-plates as well.
> I have a long-tail in my Barracuda, with the shifter relocated some 9 inches to the rear, between the buckets, on a custom adapter I whipped up. I raised the thing high enough to install the top bolt from inside the car. I haven't missed a shift since 2004, and I am using a Mr.Gasket Bang shifter (circa 1972) which is maybe 9 inches tall.... I really like it. The long tail was required to install a GVod unit.
> With the manual trans, and a regular Hurst Shifter in the factory location; I recommend a rev-limiter ............. cuz seeing the shift needle coming down from 8000 is a little nerve-racking......
If this happens to you .....Do NOT put the clutch in! Cuz;
If the lifters are pumped up, the engine will stall for lack of compression and will not restart until the lifters bleed down, which could take days. If your lifters get pumped up, keep the revs as low as you can without stalling, and just wait for the engine to smooth out as the lifters bleed down. If it won't smooth out, you can bet the valves are bent from hitting the pistons.
For this reason, I installed adjustable valve gear and run only 1/2 turn preload. Well that and 8000 rpm springs, lol. I usually shift at 7000/7200; but to do that more than once or twice, your engine needs to have some oiling mods done to help the rod bearings live.
>Your cam, if 250*@.050 will power peak around 5600, and want to be shifted around 6200 for max average power during a run; but with worked heads, they may hang on to say 6500. I only shift mine at 7000 because; Firstly, it goes there lol (I never had a SBM that lived up there before), and secondly, cuz thru dual full-length 3" pipes and dynomax muffs, the sound is horribly addicting. I just wanna do it over and over and over ........., and Thirdly cuz in First-over (I use the GVod as a gear-splitter) with 3.55s; 65mph is ~6900; but in Second gear is just ~5500. Guess which gear I use/lol.
> your car, with a 250* cam is gonna need some serious rubber in the back, in an effort to keep from wiping out around town, in turns going to WOT......unless you choke the engine with a tiny 4bbl, I guess. If you like to drift the back out, under control, 295s are not too big. Well heck; just about any cam in a hi-compression 360, is gonna be a handful at WOT with the steering-wheel Not straight ahead,lol. In that respect, the 8/1 360 is a lot more forgiving, it doesn't snap to it as radically, giving your reflexes a break; you can drive it with a hangover, the next morning. At 11.3 Scr, you gotta stay sharp, especially with skinny tires.
> Ok that's enough chit-chat for now.

 

[dhowlan]

I'm hoping there's some obvious spring thing going on with that one strut when I disassemble. I engaged 4th/od with the 3/4 lever (only) in the side cover and the other two struts are flat. Only the one adjacent the chipped stop ring is popped up.

 

[AJ/FormS]

It's hard to tell but, it appears that the energizer spring is out of place; it belongs underneath the strut.
If it is not out of place then I would suspect it is broken. The strut is supposed to have a small lip on the end that pushes the brass, to keep the spring under it. But when the strut pops out while working, the spring is free to wander around.
Yes, with a small screwdriver, or a sharp pic, you can push the spring back under the strut.
But the thing is this;
those springs have a hook on one end that that indexes into the back of any strut. And NO strut should have two springs indexed to it. So right now, you have no idea where the hooks are, and if they are not where they belong, then they are free to rotate out of place and that leaves you in the same predicament, down the road.... again.
So you gotta go find the hooks and make sure that they are properly engaged in the back cavity/ near full-length trough, of the struts.
Ima thinking the spring that is under the slider in this pic, is out of place.
So pop it underbearh making sure the spring is under it , and I think it is, move the slider over to the other side, then go look for the spring.
Remember. with the cover on, the slider only just engages the clutch teeth I'll guess a fat 1/8th inch, so only move the slider over far enough to perform this operation.. ....... else the struts will all pop out again. Sometimes you just gotta do what you gotta do, and pop them all out to go find the hooks.
Happy Hunting

 

[dhowlan]

Still not having an aha moment. I have disassembled the transmission. The synchro springs are all in place and hooked in different struts. Nothing is obviously out of place. Neither bearing has any discernible side motion.

On the plus side, I exhumed the small box containing the old parts from the y2k rebuild. Some things to note. 1) There are no syncro springs, so the ones in the trans are the originals. 2) The original syncros (with lively pink paint) range from barely worn to one that has significant wear where the strut end hits at all 3 locations. Hmm. 3) The bearings are one 307, that is garbage, and one 308SG10. The 308 is in really good shape. no noise and no side movement. It is exactly the same dimensionally as the one on the input now.

Today's plan is to put the cover on the somewhat bare case and measure the distance that the lever actually moves going into 3 and 4 and also 1 and 2. Also the distance from each to neutral. I'm also planning to take the best original syncro and stab the mainshaft and input back in to see if it will shift with that syncro.

One other thing. It seems that replacement strut springs that I see offered now have a hook on both ends. If it were y'all, would you be more willing to get new "oem" springs which may or may not be up to the original quality, or assume the originals are the best option?

 

[dhowlan]

For those playing at home, the lever moves 1/2" in either direction. Same on both.

After trying very hard to keep the problem strut assembly together so I didn't lose track of what bits caused the problem, I finally caught it doing the bad thing. Which leads me to the part that I think is causing this, that I probably would have sorted if I had actually taken the keys out earlier. What's happening is that there is a concave divot where the key is worn on the bump part. The wear is from the slider at the end which is a point. It has carved a dish in the key. When the slider moves to the middle of the key, it fall into the carved hole and the key pops up. Not the extreme pop up, but it pops up. And then the bottom end or the key smacks the synchro.

So I'm going to get all new keys (never did replace those at the previous rebuild) and the one synchro. Fingers crossed that sorts it all out.

Thank you for the assistance.

 

[AJ/FormS]

I saw that wear and dismissed it on account of I have seen a lot worse wear and the trans still always worked nice. The struts in my trans, have over 250,000 miles on them and still work flawlessly;......... and I have repointed BOTH the slider and the clutch teeth several times.i.
Since you have it all apart now, grab the slider and a strut, and lay it into the notch and make sure it fits into it properly and lays flat in it.
The sliders from the old style synchros will fit on the late style hubs with the late-style struts; but the new-style struts do not fit properly into the old-style sliders; they had different strut grooves.

IMO, the struts are not your problem, for me, the over-shifting is still on the table. When the slider is properly located and working in it's proper range, the struts never come out from under the slider, that far.
Try this; If you have an old 3-4 slider, lay it flat on the table beside the new one, and compare it's overall height which should be the same. Also compare where the fork-tracks are; flipping one of them over; making sure it is still in the same relative location. If you don't have an old 3-4slider, I think the fork tracks of the 1-2 slider are in the same location, not 100% sure..
BTW if the energizer springs are weak, this will allow the spinning slider to walk to the extent of it's travel, which, if the fork and or slider are worn, is considerably more than the design-travel, allowing the strut to pop-up on the trailing side.
I'm not convinced yet, that the fork is not bent.
>I would lay the fork on an elevated block, on the table, that only touches the rubbing surface of the pads on the fork, then measure the distance from the table to the upper edge of the pivot-pin, as far from the root as is possible. Then flip the fork over and measure again. The two measurements should be very similar.
>At the "bump part",compare the wear on the 3-4 struts to the wear on the 1-2 struts.
>Then compare the rub-bars on the ends where they push against the brass.
>You never came back with the dimension of the outter snapring thickness of the Front 307 bearing.
>Measure the depth of the rear bearing cavity, and compare it to the width of the 308 bearing.
The bearing should just fit in there, with little or no slop.
> Try to measure the distance between the clutch teeth of the first and Second gears. You may have to remove the slider. Then do the same between the Fourth and the Input gear again without the slider. Theoretically, these two dimensions should be very similar. Realistically the front is always baggier. This area is always the problem area.
Since the struts are all the same length, if the wear on the Direct-brass gets to be excessive, this allows the struts, especially with weak energizer springs, to walk out of the back-side of the slider, when selecting Third or Overdrive. I have taken apart transmissions where someone has installed an extra energizer on the Third/Overdrive side, in an attempt to limit the forward travel of the struts. I have never tried it so don't know how effective that might be and/or what the consequences might be to the shift into Direct.
>BTW; A230 struts IIRC fit into those late-style sliders. But as I recall are not compatible with the A833 struts. I forget why I nixed that swap, but I did check it out ...........about 50 years ago. So make sure your struts are all the same.

 

[weedburner]

Back when I was reworking Saginaw 4spds, I cut a large hole in the top of an extra main case so that I could verify where the installed side cover/forks placed the sliders, then re-worked the detent combs to my satisfaction. Might be an eye opener if you have a spare main case to sacrifice.

Grant

 

[dhowlan]

Thanks. I have thought how lovely that would be. Unfortunately, not a spare case in sight. We'll see how it goes with new keys and then reassess.