I've lost 4th gear!

[jvandyke]

I thought I'd do a version of Bill's 1500 gearbox tear down with my ribcase.
Background:
Went to look at a '63 Midget. Looked pretty good, drove pretty nice. Bought it.
Started heading home (family chasing in the mini van). All was well for 10 miles or so, then, while going down the highway at 65mph, it popped out of 4th. I put it back in, a few seconds later it popped backed out. Could not get it back into 4th, simply wouldn't go in. I pulled off the highway. Drove the remaining 70 miles or so in third. Went to drain the box, nothing there. (carpet glued down well so obviously it hadn't been checked in 20 years since it's re-do). Tried various incantations of oil, Marvel Mystery oil, refill drain, repeat. I did manage to muscle it into 4th once or twice. Found decent used box, swapped them. Driving happy (although replacement box isn't perfect either).
It's now winter, workroom is somewhat cleaned up so I decided to tear this thing down and see what is what.
On the bench I can spin the input by hand and move through gears but it doesn't always result in something on the output end. 3/4 selector "looks" weird. Sometimes lots of resistance in all put 3rd gear, couldn't even get reverse on the bench (I think reverse is somewhat hard to engage by design).
All the gear teeth look pretty good to me, not much wear that I can see at this point.

In the initial drainage there were a few little bits of metal (picture to follow).
So far in the tear down (remote housing and rear extension removed) all I've seen was what looks like a roller from a needle roller bearing that was under the extension housing, OUTSIDE the main gear box (between the two pieces), how could that get there?

Taking any guesses as to what went bad, I'll have to come up with a prize.
What would one expect to fail in a gearbox that was running bone dry?

Haynes manual seems pretty comprehensive so I don't think I'll do a step by step. Maybe just report my newbie observations and pitfalls.

#1 removing rear extension, manual says to pull back and turn the extension housing counter clockwise. I found it makes a big difference where the gear selector rods/forks are. I couldn't get it until I looked in there, saw things were getting hung up, moved the 3/4 selector back to more of a neutral point and it came off, maybe putting the box in neutral from the start is wise.

Question #1: What is the purpose of the two springs behind the side cover?

 

[ChrisS]

Question #1: What is the purpose of the two springs behind the side cover?

They put pressure on the detent plunders for the shift rods.

 

[jvandyke]

Looked like just a dead end behind them though, didn't look very close either.

 

[Spridget64SC]

Let me try some thoughts:

Lack of lubrication can cause all sorts of bad things. If there are still all the teeth on the input gear and the matching laygear gear, then-

Third motion shaft spigot bearing (That little caged needle roller bearing in the back of the input shaft) failed/broke. Stuff in the main case spins and throws oil(and other things) up into a catch ledge on the drive side of case. The ledge is sloped to the rear to oil the stuff in the extension through a hole and passage. Often find things embedded in the "sludge" under the main shaft there.

3/4 slider often gets beat up on the internal engagement teeth making engaging 3rd or 4th gears very difficult and sometimes impossible. Bad syncros/dog teeth on gear usually cause this.

Recommend a complete teardown. No oil is very bad for the gearbox parts. A through inspection of layshaft, laygear bearing surfaces and the other bits and pieces is a must do.

Rod Hanneman over at Spridgetech in Brighton, MI is a good source of lots of used Spridget parts. Might be able to help out with some more localized diagnosis as well.

HTH,
Mike

 

[jvandyke]

The pieces I've found so far look to me to be from a caged needle bearing.
This is exploratory surgery, if too many pieces need replacement, I won't fix it up. I like to take things apart and learn. Hopefully it is salvageable and I can get it ready for when the current gearbox goes south, but if not worth saving, at least I learned something.
Thanks for explanation of oil/catch tray and all that, explains how that needle got behind the gearbox.
Will be fun to discover more.

 

[regularman]

4th should not be a real "gear". It should be just the input shaft locking to the output shaft for a 1:1 ratio. It has got to be in that linkage or detents or a bent fork or something. You found parts though so that is not a good sign.
Hopefully is something simple but you can't do anything with it in the car. Its no fun having to pull the motor but that is what you have to do.
I would recommend looking it over real good before pullin it all apart. Then you might be able to order something that you need. I would want to take it apart one day and put it back together the next, without too much time in between so you remember how it goes back. I have not found a book that covers every detail. I got a good one in a box if you get sutmped on putting it bakc together and need me to look at it.

 

[jvandyke]

I would want to take it apart one day and put it back together the next.......

Well that was my thinking too so I got a known good box and did the pull and swap immediately after getting the car home. Been driving with the second box for 5,000 miles now. This one is being torn down and inspected at my leisure.
Anything to keep the car roadworthy when it counts! Winter is the time to tinker. I doubt I'll swap them back even if this one is rebuildable unless some other reason for pulling the motor pops up (which it will). When it does, I'll hopefully be ready with a "better" box....maybe.

 

[Hap Waldrop]

I'll throw this in, Spridget64SC, Mike Miller is a long time buddy of mine, and if any of you ever need a gearox built, he does a mighty fine job, Mike over the years has built more than a couple gearboxes for me for my race car and for customer's of mine as well.

 

[jvandyke]

Picture of gears.
and flotsam. All but the shiney bit on the right came out of the box, the shiney one was in between the box and extension.
I tried to make these really big.

 

[Spridget64SC]

MM:
Gearbox needs a complete tear down. 3/4 Shift fork is totally toasted. The 3/4 slide gear has totally worn through the brass fork. The little needle rollers still look like the spigot bearing that is in the back of the input or was. I would hazard a guess here that there is a lot more that is going to need to be replaced. If you decide to fix, all the new stuff you would need would be rather costly. Chase the good used route for the hard parts. Buy new bearings and synchro's, but used gears, forks and stuff like that. This is one of those situations where you will need 2 or 3 trany's to put one back together. Some parts from different year cars can be mixed, some can't. If you get different part numbers together and need to know, let me know, I've got some old interchange sheets that help ID the various parts.

Hap, Thanks for the cudo's. In 30 years of messing with the LBC's, I have built and rebuilt well over 500 or so gearboxes. Everything from Ford/Lotus, TR-6, Spit, MGA/B (no overdrive) and Spridget. I've even made my own Webster conversion boxes for my Spridget racers. Those are the ultimate in race gearboxes.

Take care and good luck with the trany repairs. A real winter project for sure.
Mike

 

[jvandyke]

Thanks a ton for the feedback. I thought things in the 3/4 slider were awkward. I won't expect to rebuild it then, but will likely tear it apart for the learning experience.

 

[jvandyke]

Did some more tear down.
Can't quite figure out the "first motion shaft", there's still a gear hanging on the inside, just keep pushing from the inside out (the bearing (which is trashed) is free already)? (third from last picture)
But take a look at what I think are the lay gear thrust washers, looks like it was running off center for a bit, no? Spooky (last two pics)
pictures

 

[bugimike]

Can't see the pix you are referring to, but those laygear thrust washers DO have eccentic grooves machined into them for oil circulation!!!

 

[DrEntropy]

Mouse over the last word in his post, Mikey.

The thrust washers do appear to have been "set" in one position rather than rotating.

Shouldn't need to force anything... if the gear is too large to fit thru the opening it needs to come out from the access hole in the case. Remove the bearing from it and lift the first motion shaft out. Been years since we've had a Spridget box apart but ISTR that's the method.

Those needle bearings appear to be the ones in the input shaft. Were they in the bottom of the case when you drained it, or fell away when you pulled the mainshaft out?

 

[jvandyke]

Oh, okay I thought the grooves where funny wear. See? I'm learning lots.
Pictures don't come up on that page? Maybe I can link to them directly. Still wondering about that last gear hanging onto the inside-the-box end of the input shaft. The bits and pieces look pretty good to me so far, if nothing else I'll save everything for the future. I did pull a newbie and allowed the spring loaded balls and stuff to fly out of that one gear. I even knew they were there, just playing to see how it moved back and forth and went a tad too far and BOING all over the place, now I have to figure what I'm missing so I can start searching.

 

[DrEntropy]

:lol:

I shoulda posted to "fiddle" with those clusters INSIDE a paper grocery bag to retain th' "BOING" bits and keep 'em from crawlin' under tool boxes and washing machines. :wink:

<span style="font-style: italic">
EDIT: Photos show up fine.... it's Mike's problem, not your post.</span>

 

[jvandyke]

Mouse over the last word in his post, Mikey.

The thrust washers do appear to have been "set" in one position rather than rotating.

Shouldn't need to force anything... if the gear is too large to fit thru the opening it needs to come out from the access hole in the case. Remove the bearing from it and lift the first motion shaft out. Been years since we've had a Spridget box apart but ISTR that's the method.

Those needle bearings appear to be the ones in the input shaft. Were they in the bottom of the case when you drained it, or fell away when you pulled the mainshaft out?

I'll have to look at Haynes again. I expected to be able to pull the input and bearing out the front, everything else would be left behind in the box.
Yes, the needle bearing bits were in the bottom of the box. The front bearing also has part of the metal ball "retainer" things floating freely around the bearing.
Sure would like to know how this thing lost it's oil. There was no evidence of leaking when I bought it and none after I refilled either so I'm thinking it was never refilled. PO only drove it very short distances and very infrequently though he told me he took at least one 120 mile trip years ago.

 

[startech47]

Should be 3 balls and 3 springs. The thrust washers are both thrust washers and little oil pumps all in one.

 

[Spridget64SC]

There is a snap ring on the input shaft bearing. Tap the input shaft forward about 3/8". Use two medium size flat blade screwdrivers to pry it off the bearing. Get it started and it will "peel" off. Then you can tap the input back through the bearing bore of the main case. The "Dog Teeth" on the gear are usually too big to go through the bearing bore. The best tool for driving the rear bearing plate out is a long brass punch. I use a Craftsman line up tool. Not what it is suppossed to be used for, but it works real well. Puts some dings on the underside of the plate, but it doesn't show.

I've got a special pair of pliers that I bought to remove the snap ring since I build so many of these gearboxes. A inexpensive set of needle nose could be ground to to the same thing for the occassional user.

I have seen more than one gearbox where the individual forgot to put oil in it after I returned it to them nicely rebuilt. One lasted almost the whole race weekend.

Have a Merry Christmas and a great New Year,
Mike

 

[jvandyke]

Great thanks. I'll investigate further when back home. I got the rear bearing case out easily, punch from the inside, then did the Haynes method of removing the speedo gear/spacer, putting the nut back on and tapping on it from the back, opened up enough to allow some prying and it was free. Of course as it came backward the two parts of the shaft separated and things fell apart so I'm not sure how they were but will figure it out. I'm guessing I'll at least need the new brass 3/4 fork which may be hard to come by? I'm willing to try and rebuild this if I can do pretty cheaply, I'm thinking less than $100 in parts and it's worth it, more than that and I'll let it sit in pieces waiting to be parted out. I'll try and get some shot of the synchros and laygear and such to see what folks think of their condition. At least one tooth on the laygear is chipped pretty bad but nothing else looks at all bad to my very inexperienced eye.