Can't get into top gear

Common upgrades - A-Series mods, brakes,wheels, handling, interior.
User avatar
emjay
.
Posts: 265
Joined: 6 years ago
Location: Eastern Pennsylvania, USA

Re: Can't get into top gear

Post by emjay »

Understood. As you were holding the lever towards fourth you no doubt are feeling the "teeth" of the snychros. The most likely problem is a dedent ball has fallen out of place and is sitting under the front cover preventing the shift rod from moving all the way or possibly something wrong with the front cover. The only thing to check to make sure it's not something else is to take the remote shifter off and see if the 3-4 rod can move forward the proper distance. Of course all of this has already been stated. With the box in your storage room I'd take the front cover off first and either collect the loose ball or confirm the pocket in the front cover for the three selector rods has enough clearance. After that it gets more involved but at least just pulling the selector rods isn't too bad. Just watch for all the balls and oblong ones. If you do find a ball under the front cover, you may be lucky and it was an extra one. With the side cover still on select one gear at a time and then make sure the other two rods can not move. Also check that when in neutral it takes the same amount of force to move one rod at a time. You'll need to have the remote sifter off to get access to the selector rods or forks. You'll soon will identify which dedent is not operational. Gearbox work is rather pleasant, it's just all the fuss to get to that point.



User avatar
Fingolfin
.
United States of America
Posts: 257
Joined: 9 years ago
Location: Missouri, USA

Re: Can't get into top gear

Post by Fingolfin »

So the engine and gearbox are now out of the car, and the gearbox partially disassembled (remote control, rear extension, and side cover removed). The selector rods are exposed on the back end where the remote control linkage engages.

I can pull and push on the first and second selector rod, and the action is like you'd expect, positive "clunks" at both ends of the travel.

The third and fourth selector rod moves only about a centimeter, and I'm pretty sure it's only engaging third.

I removed the setscrew from the third and fourth fork, and it has no additional travel than the rod does, though that may just be that it's seized onto the rod from age.

Next I'll take a look under the front cover as Emjay suggests, but for now I'm taking a rest!



User avatar
Fingolfin
.
United States of America
Posts: 257
Joined: 9 years ago
Location: Missouri, USA

Re: Can't get into top gear

Post by Fingolfin »

Something unrelated I've noticed, the speedometer drive gear on the mainshaft is rather rusty and pitted. Is that critical enough that it should be replaced? :roll:



User avatar
Mecanglais
Formally known as chesney
France
Posts: 2189
Joined: 9 years ago
Location: France

Contribution Stars

Re: Can't get into top gear

Post by Mecanglais »

When you removed the locking bolt, could you then move the selector fork and engage 4th gear?



User avatar
Fingolfin
.
United States of America
Posts: 257
Joined: 9 years ago
Location: Missouri, USA

Re: Can't get into top gear

Post by Fingolfin »

No, there was no change. The fork was not free from the shaft even with the locking bolt (what I referred to as a setscrew) removed.

I just took off the front cover, and there were no loose balls anywhere, and the motion of the third and fourth shaft was unchanged (still only about a centimeter back and forth).

I guess next step is to try to remove the selector rods and inspect the forks and such. I've already committed to a full stripdown and rebuild, I've ordered all the bearings and such. (Good thing too - the front input shaft bearing has what feels like a LOT of sidewise play.)



User avatar
MM
.
United Kingdom
Posts: 3796
Joined: 9 years ago

Re: Can't get into top gear

Post by MM »

Regarding the speedo drive cog, it would be advisable to replace it if it's as bad as you suggest.

I would try using penetrating oil on the 3rd/4th gear selector fork to allow it to be freed off so you can see if the set screw is nestling into the groove cut into the rod.

Also worth checking someone hasn't fitted smoothcase selector rods, as they are different lengths and have different detent positions:


Input shaft can be fairly slack, since it is supported at the front (or should be!) by the bronze spigot bearing in the end of the crank. Obviously, check for noise/roughness in the input shaft bearing though and replace if necessary.

Good luck with the rebuild. I found this article helped alot with mine:
http://www.dorsetmmoc.co.uk/wordpress/t ... ebuild.pdf


Maurice, Kent.
1970 Trafalgar Blue Traveller

http://retrorides.proboards.com/index.c ... read=37056" onclick="window.open(this.href);return false;

User avatar
Fingolfin
.
United States of America
Posts: 257
Joined: 9 years ago
Location: Missouri, USA

Re: Can't get into top gear

Post by Fingolfin »

Thank you for that information, MM, I will check the part numbers and lengths of the selector rods when I can. I've also got checking and if necessary renewing the pilot bearing on my list.

In one whirlwind evening I have got the gearbox disassembled!
105943595_3322234741161993_2082034716916887474_o.jpg
105943595_3322234741161993_2082034716916887474_o.jpg (376.57 KiB) Viewed 39 times
105943595_3322234741161993_2082034716916887474_o.jpg

Here are some things I discovered:
  • Several of the detent ball / plunger things were missing, or had springs missing, etc. I have not found them inside the gearbox, so I can only assume that someone tried to reassemble it previously and left them out. Of the ones that were present, I have not been able to remove two. I think I need some stronger magnets.
  • I think I was able to engage fourth gear once by hand, manually moving the selector fork as Mecanglais had suggested. But immediately after, the selector rod seized almost solid, and it was a terrible trial getting the selector rods out. My hypothesis is that the lack of detent ball / plunger things allowed the gearbox to select two gears simultaneously, locking it solid.
  • The nut on the mainshaft was slightly loose. It had not backed off, retained in place by the lockwasher tab, but it was loose enough to turn side to side under finger pressure.
  • I am no expert and have only given cursory glances so far, but none of the gears look badly worn, and the selector rods and forks have no obvious wear.
Tomorrow is my birthday so I don't expect to do any major work, but I'm satisfied with the progress I've made so far. I think my next step, whenever I take it, is to get all these parts cleaned and organized and intimately inspected. Thanks for your continuing help!



User avatar
Mecanglais
Formally known as chesney
France
Posts: 2189
Joined: 9 years ago
Location: France

Contribution Stars

Re: Can't get into top gear

Post by Mecanglais »

Lack of detent springs sounds ominous.
Did it still have the dowel between 1st/2nd and 3rd/4th selector? If the detent springs are missing or the forks are slightly misaligned then the dowel will actually prevent selector movement.

Mainshaft nut probably won't have had any ill effects, eventually it would probably allow the Speedo drive to spin on the shaft though.

Worth checking the synchro while out, look for sharp, pointed teeth, particularly when worn on one side.

When you manually selected fourth gear, and the shaft seized solid, that was with the locking bolt removed at a guess, was the fork free to move on the selector (ie, past the dimple for the locking bolt) or still moving with the selector rod? If you have the selector rod to hand, try it in the housing, is it free to move? The hub itself slides easily into 4th position over input shaft gear? It sounds like it might have been apart by someone a bit ham fisted, best make sure there are no burrs in the casing, and that the dowel that fits between the selector rods is a dowel that is of the right dimensions and not something someone has put in because it looks similar and they had it kicking around on the floor at the time!

Oh, and happy birthday.



User avatar
MM
.
United Kingdom
Posts: 3796
Joined: 9 years ago

Re: Can't get into top gear

Post by MM »

Many Happy Returns on your birthday! :usa2:

You could use compressed air from a compressor or foot pump to get the stuck detent plungers out; a bit of WD40 or similar may help...

Certainly sounds like the gearbox was rather poorly assembled. :roll:


Maurice, Kent.
1970 Trafalgar Blue Traveller

http://retrorides.proboards.com/index.c ... read=37056" onclick="window.open(this.href);return false;

User avatar
emjay
.
Posts: 265
Joined: 6 years ago
Location: Eastern Pennsylvania, USA

Re: Can't get into top gear

Post by emjay »

I agree moving the fork without the rod moving was the last test to confirm if it was a rod issue or a gear issue. The rods and forks typically are tight fit by design. Rotating and pulling is often required which I'm sure you did. With missing dedents it's obvious someone "rebuilt" this box and hopefully that is all that is needed. The oblong dedent especially are hard to get out. It'll be a matter of working them back and forth with a small screwdriver or such and some oil. Once you get them into the long bore hole, a small wire will be need to push. Once out clean the bores out with an appropriate drill bit, 5/16 as I recall. Working it by hand is enough. The balls are common sized ball bearings but if you are missing some of the oblong ones, I have should have some loose ones. Of course test the engagement of the 3/4 wheel on the main shaft before putting it back in and assembly just the rods and dedents to make sure each moves individually and just one at a time. The main main area to check is the layshaft. The area where the needle bearing run is often crazed.



User avatar
Fingolfin
.
United States of America
Posts: 257
Joined: 9 years ago
Location: Missouri, USA

Re: Can't get into top gear

Post by Fingolfin »

Thanks everyone, those are some good suggestions, and thank you also for the birthday wishes. 8)

The missing plungers / balls were Moss items nos. 75 and 76 https://www.moss-europe.co.uk/shop-by-m ... this link. Moss indicates both of those as being interlock items.

The side plungers, nos. 80, were present with their springs.

The underside screws were in place but at least one (unfortunately I don't recall which but it wasn't the smaller one, the reverse locating peg, item no. 37) was missing its spring.

I'm going to do a careful inventory of all these items, and maybe renew all of them just to be safe, once they're all removed. (The only one still in the gearbox is one of the side plungers - there seems to be a burr in its bore keeping it in place. More fiddling ahead.)

When I manually selected fourth, the fork was free to move on the selector rod. With the rods removed, all the forks are free to move on them. I'll reassemble them into the box and see if I can replicate the movement problem after I clean everything. And I already have a brand-new layshaft in my parts boxes! :lol:



User avatar
Mecanglais
Formally known as chesney
France
Posts: 2189
Joined: 9 years ago
Location: France

Contribution Stars

Re: Can't get into top gear

Post by Mecanglais »

I have a fine pointed pick bent to a smooth 90 degree curve which is brilliant for prodding in the selector rod holes and pushing dowels out of their slots :D

Keep the old layshaft, they make brilliant punches/drifts.

I'm not able to open the link properly, perhaps it's specific to your 'basket', but if you have documented and recognised what is missing you can't go far wrong. Just need to put it all back in the right order now! Double and triple check all the balls and dowels are in their right places, with their right springs, and double and triple check the end float, particularly if you are changing the bearings, you may need to add a few shims.



Post Reply