Transmission rebuild- can’t get reverse

Russe11

True Classic
With much help from Steve Hoelscher’s “5-Speed 101”, I’m rebuilding the transmission with Dad. I must be missing something.

I’m pretty sure I’ve got the shift forks, linkage forks, selector rods, interlocking ‘beans’, detent balls and springs all in their proper positions, but when I grab the shift rod and try to go through the pattern, I cannot engage reverse.

Any ideas will be appreciated
Brian
 
Cannot move the selector into the reverse position (rotated counterclockwise facing the transmission so looking towards the rear of the car, pulled out) or can move the selector into that position but no reverse when you do?
 
Try getting it into reverse without the shift linkage connected at the lollipop. In other words, put vice grips on the trans shifter input shaft and try shifting all of the gears from under the car. It could just be the lollipop adjustment.
 
Cannot move the selector into the reverse position (rotated counterclockwise facing the transmission so looking towards the rear of the car, pulled out) or can move the selector into that position but no reverse when you do?
Selector will not move into the position for reverse.
1,2,3, & 4 are pretty easy. 5 takes effort. The twist is fine, but the push is harder than the others- I’m attributing that to the stiffer spring for the detent ball. But twisting from neutral, then trying to pull out for reverse will not go.
Brian
 
Try getting it into reverse without the shift linkage connected at the lollipop. In other words, put vice grips on the trans shifter input shaft and try shifting all of the gears from under the car. It could just be the lollipop adjustment.
The transmission is sitting on the workbench.
Trying to move the shiftershafter as you’ve described
Even tried with the extension cover removed, so I could pull up on the 5th shifter fork.
 
Have you tried rotating the gears (from the axle flange) to allow the box to find reverse? I know mine will refuse reverse occasionally, and letting the clutch out in neutral spins the internals and when pushed back in, the car goes into reverse with no difficulty.
 
What parts did you replace when you rebuilt the box? I rebuilt a 124 5 speed transmission and when out of the car it was very difficult to shift. Once everything was set up back in the car it was like brand new. As jefco notes, when the internals are rotating it is easier to find gears. Make sure everything is right before you get it back in the car though.
 
Reverse is the only gear where you actually engage gears, so mis-alignment of the teeth can cause difficulty with engagement. All the forward gears are in constant mesh, and selection is locking the gear to the cluster shaft to engage drive.

I'm with the "spin the trans internals" and try again suggestion

SteveC
 
Have you tried rotating the gears (from the axle flange) to allow the box to find reverse? I know mine will refuse reverse occasionally, and letting the clutch out in neutral spins the internals and when pushed back in, the car goes into reverse with no difficulty.
Reverse is the only gear where you actually engage gears, so mis-alignment of the teeth can cause difficulty with engagement. All the forward gears are in constant mesh, and selection is locking the gear to the cluster shaft to engage drive.

I'm with the "spin the trans internals" and try again suggestion

I had the same thought. I haven't put the stub-shafts in yet, but with the extension case cover removed I rotated the innards from that end, hoping it would allow it to move... But no.

Thanks for the suggestions.
 
What parts did you replace when you rebuilt the box? I rebuilt a 124 5 speed transmission and when out of the car it was very difficult to shift. Once everything was set up back in the car it was like brand new. As jefco notes, when the internals are rotating it is easier to find gears. Make sure everything is right before you get it back in the car though.
Good thoughts.
This rebuild used the best parts from two transmissions (80 & 81), plus a new 1/2 sliding gear, reverse idler gear & its shaft. The '81 is what was in the car, and had worn synchros on 3 & 4, wouldn't stay in reverse, and sometimes popped out of 3rd. The '80 was purchased in unknown condition. It turned out that a prior owner had obviously replaced 3&4 synchros and probably the 3&4 gears. The case had a crack in the bottom. So, The input shaft & lay shaft are from the 80, plus a new 1-2 siding gear, new reverse idler and shaft. Case, differential, and all the linkage parts are from the 81.
Before closing up the case, I could move the selector into all 6 positions.
After putting the case halves together and installing 5th gear, I can't select reverse.

Brian
 
Brian,

There are several reasons you may not be able to engage reverse.

Did you check the operation of the reverse lockout mechanism?

Yes, the 5th/Reverse detent spring is stiffer and therefore causes more resistance. But also, the centering spring puts a lot of preload on the 5th/reverse shift rail and that makes it more difficult to move.

Steve's note that the gears themselves have to engage is correct. The reverse idler has to be moved to engage between the reverse gear on the input shaft and the reverse gear on the outside of the 1-2 slider. If the reverse idler teeth clash with either of those the gear resists engagement. Therefore it takes a fair amount of force to engage reverse when moving the rod by hand.

Spinning the lay shaft offers no assistance in aligning the gears. The shaft turns inside of the gearset unless one gear is engaged. So you must turn the input shaft and that can be reached from the bellhousing side. If reverse is difficult to engage try turning the input shaft to re-index the gears. It may take several tries.

You should always inspect the components carefully. The internal translator linkage especially. The lug at the end of the translator fork can get bent and cause all kinds of shifting problems. Also, the main shift rod and the shift rails can get fouled. Inspect them for damage as well as the case bores. And make sure you preoiled all of those parts on assembly. If the parts don't have lubrication they will not want to move.

Also, make sure the 5th gear slider isn't hanging up on its hub.

Then there is there is the issue of the unit having been rebuild previously. You never know what a previous rebuilder might have done. So inspect everything and make sure they haven't done something like use the wrong reverse fork.
 
Brian,

There are several reasons you may not be able to engage reverse.

Did you check the operation of the reverse lockout mechanism?

Yes, the 5th/Reverse detent spring is stiffer and therefore causes more resistance. But also, the centering spring puts a lot of preload on the 5th/reverse shift rail and that makes it more difficult to move.

Steve's note that the gears themselves have to engage is correct. The reverse idler has to be moved to engage between the reverse gear on the input shaft and the reverse gear on the outside of the 1-2 slider. If the reverse idler teeth clash with either of those the gear resists engagement. Therefore it takes a fair amount of force to engage reverse when moving the rod by hand.

Spinning the lay shaft offers no assistance in aligning the gears. The shaft turns inside of the gearset unless one gear is engaged. So you must turn the input shaft and that can be reached from the bellhousing side. If reverse is difficult to engage try turning the input shaft to re-index the gears. It may take several tries.

You should always inspect the components carefully. The internal translator linkage especially. The lug at the end of the translator fork can get bent and cause all kinds of shifting problems. Also, the main shift rod and the shift rails can get fouled. Inspect them for damage as well as the case bores. And make sure you preoiled all of those parts on assembly. If the parts don't have lubrication they will not want to move.

Also, make sure the 5th gear slider isn't hanging up on its hub.

Then there is there is the issue of the unit having been rebuild previously. You never know what a previous rebuilder might have done. So inspect everything and make sure they haven't done something like use the wrong reverse fork.
Thanks, Steve. Lots of stuff to check, there. That's great.

Good point about needing the INPUT shaft to turn in order to help reverse to line up. I missed that detail. And that would be EASY :)

The 'internal translator' and the reverse-lockout mechanism seemed to be functioning properly before I put the other half of the case on. And the linkage didn't seem to be fouling on itself from being bent, but without the other half of the case, perhaps the selector rods were moving side-to-side enough to give clearance which disapeared when it was assembled. That warrants closer inspection, too.

I wish I had your experienced eyes when inspecting for abnormalities. Thankfully, I've got your instructional documentation plus more from Bernice. And with two sets of parts I at least have something to compare to. If I see differences, I can swap and keep whichever works.

Brian
 
Selector will not move into the position for reverse.
1,2,3, & 4 are pretty easy. 5 takes effort. The twist is fine, but the push is harder than the others- I’m attributing that to the stiffer spring for the detent ball. But twisting from neutral, then trying to pull out for reverse will not go.
Brian
The transmission is sitting on the workbench.
Trying to move the shiftershafter as you’ve described
Even tried with the extension cover removed, so I could pull up on the 5th shifter fork.
It may not necessarily be an internal problem. I had a very similar thing happen on a trans I recently took out of storage. It was in excellent condition when it went into storage, but after putting it on the bench and filling it with lube, I could not get it into 5th or reverse. I thought maybe something had been disturbed internally while being stored. However I realized a lot of the problem was trying to select the gears with just a pair of vice grips. It is very difficult to get the shaft to go in and out while holding in the turned position. Especially when the trans is not secured to something. So I made a simple "T" handle to bolt to the selector input shaft. That way I could get a good grip to both twist and push/pull it with one hand. I also used a short piece of old 5/8" heater hose on the trans main input shaft, attached to a cordless drill, to spin it with the other hand while shifting it. Then I could get all of the gears. The more I shifted it the easier it got. Apparently the lube needed to work its way into all the little bits inside.
 
Sorry I'm so slow in reporting back... It'll probably be Monday by the time I'm able to work on it again.
But just to tide you over, here's a picture from last Monday's time with Dad:

Dad & Transmission.jpg
 
With a better grip, provided by a PVC T-Handle, and a hole drilled in the bench top to hold a stud in the bell housing, I was able to select reverse. Here’s a picture of the handle

IMG_1016.jpeg


It’s kind of anti-climactic, isn’t it?

It sure looks like the selector shaft moves a long way, but the 5th gear fork still fits under the extension cover. Here’s a picture showing the 5th gear fork with reverse engaged.

IMG_1014.jpeg


Thanks, everyone, for the tips and encouragement

Brian
 
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Well, I guess my last post was premature...
It's true that I was able to select reverse, but the force required really was excessive. And the T-handle actually got a little help from the other end, tugging up on the 5th-gear fork (which can't happpen when it's in the car). So, I decided to tear it back down and lubricate things more generously, as I reassembled. With it back together (to the same point - no cover on the end) I couldn't move the selector at all. I lifted the 5/reverse rod (freeing the interlock 'beans'), and was able to engage 1,2,3, & 4, but with difficulty. 5 with more difficulty, and reverse not at all.

I'm suspicious of the interlock 'beans' and the detent balls not holding the selector rods in alignment with the internal translator and reverse lockout mechanism. We'll be opening it up yet again, this weekend, and I'll update then.

Brian
 
So, just check one thing. I have put the reverse gear selector in upside down before. That prevents you from going into reverse. On a 4 speed, it also causes the car to lock 4th and reverse at the same time. Good party trick to impress your friends. More pictures always help.
 
Thanks for another good suggestion. I'm confident that it isn't that specific problem, as I could cycle through all 6 positions before putting the case halves back together. But I suppose it is possible that something is misassembled.

It did seem to want a little help with lining up the mechanism's 'finger' into the appropriate slots on the selector rods. With the transmission standing on the bell bousing (as pictured in post #14), the rod for 5th/reverse wanted to 'fall' toward the workbench, which locks the other rods from moving.

I'll try to get more pictures when I'm in there again. I know that's helpful to the folks who are trying to help me. And even for the folks who may be learning something from the shared experience.

Brian
 
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The shift rails are held in the neutral position by the detent balls and springs. The Interlocking "beans" do not do this. Their function is to transfer the shift rail movement to lock the other shafts. Removing the preload on the detents will allow the rails to float and potentially bind the other rails.

Its time to review the basics; inspect and check the function of each component, starting with the main shift rod and going through to the gears themselves. (Main shift rod, its fork, translator, reverse lockout, reverse and 5th forks, shift rails, detents, interlocks and the gears themselves.
 
Thanks, Steve. I appreciate your input.

Yes, I get it. When the transmission is in neutral, the spring-loaded detent balls should hold the shift rails in position with their slots in line with the finger of the intermediate mechanism. When any one of the rails is displaced, the interlock beans should then hold the other two rails in place.
I'm not confident that the detent balls are holding things in line well (5th/reverse rod dropping toward the workbench), or that the interlock is working well preventing motion when any of the rails is displaced.
I agree that I need to confirm proper function of all this stuff. While those items are the most suspicious to me (at this point), I'll try not to let tunnel vision keep me from seeing trouble with other parts.

Brian
 
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