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Center shift transmission rebuild.

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Johnny

Johnny

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Considering rebuilding my center shift transmission on my BJ7. 1st gear is completely gone, and reverse isn't much better. Also the laygear to 1st is also all chewed up. I already have the transmission out of the car sitting on my workbench with the top off. What's next? I have the workshop manual and I suppose I have to remove the OD next before I can remove the gears.

Who has done a rebuild on a center shift transmission? And how difficult was it?

Also, has anyone bought one of the AH Spares reconditioned laygears? Their considerably less expensive than a new one.

Thanks to all responding.
 
Hey John,

I think that Dick Solomon is our NTAHC resident transmission guy. He might be able to answer your questions.

If youi don't have his Email, write me and I can send it to you.

MY Email is at the bottom of the www.ntahc.org home page.

Tim
 
The rebuild is not difficult, but you will have to follow the procedure in the manual. There's little difference in procedure between the side and center shift boxes.

I bought a remanufactures laygear from Quantum Mechanics, and the workmanship is gorgeous! Time will tell how long it holds up :wink:

I'll be doing a pictorial essay, so to speak, on a complete polymer coating and rebuild of my sideshift's internals sometime in the near future (nearly all the gearbox parts have already been coated with a dry-film polymer lubricant) but that may not be soon enough to help you.

My best tip, is to clear off a long workbench, and lay out the parts in the order you take them out. That's how I did my first gearbox, probably thirty-five (35) years ago, and I've probably done at least a hundred (>100) British gearboxes since; MGA/MGB, MGB all synch, Spridgets, ALL the boxes fitted to Big Healeys (including BN1 100), plus 4 & 5 speed Triumphs, Harleys and ?
 
randy, good advise! specialy for a first timmer i would add take pictures-- , dont be fooled by a syncro that "looks" o.k. compare all of them to a new one, look for wear and
grooves, hair line cracks etc., i stalked ebay and craigs list for several months and was able to get all n.o.s. stuff for my rebuild it cost me less then buying all repros,timming is everything!, remember that bj7 boxes look the same as a bj8 box but some of the internals are not the same, order the correct stuff, and yes first read the manual or youll lose your balls. :yesnod:
 
Johnny said:
I have the workshop manual and I suppose I have to remove the OD next before I can remove the gears.

Who has done a rebuild on a center shift transmission? And how difficult was it?

Also, has anyone bought one of the AH Spares reconditioned laygears? Their considerably less expensive than a new one.

Thanks to all responding.
Click to expand...

Hey Johnny,

I've rebuilt mine 4 times in a two month period. I helped an overqualified Healey mechanic. He's the mechanic the vintage race guys use. Reason it took four times is because we could not find the good stuff, as in gears. Tried Moss, his stuff and even got a bad first gear assembly from Dennis Welch. That hardly ever happens he told me. Welcome to my world I told him. I was lucky to find some NOS on Ebay and it solved my problems. By the way, please share with us where you know where to get new laygears. The only new one's I'm aware of will be NOS, which I could not find. All the other remanufactured ones available weld a new gear on the shaft. Just like the one I ended up using.

I wish you luck. If you replace with NOS, it will go smoothly with no surprises when you take it out for a spin. Aftermarket stuff may look like it's the real deal, and even go in. Just keep your fingers crossed. Ask me how I know.

Cheers,
Roger
 
anthony7777 said:
ausmhly, where did "johnny" mention he could get "new laygears"? didnt he say "reconditioned", or am i missing something? :crazy:
Click to expand...

"Also, has anyone bought one of the AH Spares reconditioned layers. Their considerably less expensive than a new one."

Where does one find a new one...aka NOS.
 
Thanks for posting Randy, and thanks also for the encouragement. I would like to know "Quantum Mechanics" email or website address? I'd rather purchase from someone over on this side of the pond. Would you reccomend replacing the layshaft, as a matter of fact, or necessity.

Here's the address for AHspares reconditioned Laygear.
https://www.ahspares.co.uk/products/productdetail.aspx?GUID=a7ebfe05-e0cb-43bc-8bcd-b918a534d436
Their price, $199.68 plus shipping. There new one was considerably more.

Again, thanks to all who responded.
 
AUSMHLY. i got mine from ebay wrapped in original oiled paper and box, guy didnt know what it was and no one else it seems was looking for one, like a said it took me months to get all the new parts, time-in is evy-thin! :savewave:
 
johnny, quantumechanics email add: john@quantumechanics.com, great guy, i spent some time with him at his shop about 20 min. from me, traded an overdrive i rebuilt for some other stuff i needed, he pretty much gave me a bell housing to use for my rebuilt engines dyno runs, as far as inspecting a laygear just read what it says in the manual, also look for sharp edges, over rounded edges, cracks, chips, missing bits etc, youll know then if you need to change it. and the bit about "losing your balls" well youll find out when you start taking the case apart. :savewave:
 
AUSMHLY said:
anthony7777 said:
ausmhly, where did "johnny" mention he could get "new laygears"? didnt he say "reconditioned", or am i missing something? :crazy:
Click to expand...

"Also, has anyone bought one of the AH Spares reconditioned laygears. Their considerably less expensive than a new one."

Where does one find a new one...aka NOS.
Click to expand...
Sorry, my bad. AH Spares does list new ones but when you click on the part # it's no longer available. They do have the reconditioned one's available with exchange. Checking on "Quantum Mechanics".

Earlier I mentioned should you automatically replace the "Layshaft" when you replace the Laygear? Or, is there something I should look for, such as "bent, worn etc.?

Thanks to all who responded.
 
johnny, generally the laygear itself suffers the most significent amount of damage rather than the shaft but i have seen them beat up as well under very heavy loads such as when bearings go astray or racing and/or intended heavy abuse, in addition dont overlook the condition of the forks, as you study the mechanical arangement of the trans., you will be able to understand the importance of each and every segment within and the association between them all, when ive discovered one problem with any part of a healey trans, i usually find a trail of one of the parts that slowly went bad being followed by the gradual failure of the others, i have noticed that most of these problems begin with something simple as improper lubrication used in the unit or not being serviced then one or more inept drivers that bang up the syncros that start gears grinding that leads to displacing bits of metal so on and so on, sometimes if a driver is alert such as an invested owner this chain of events can be identified early and help stop the deep damage from happening, my car a 1963 bj7 im sure has had many drivers with or without the ability to operate "the beast", take your time, study the unit, ask alot of questions, be methodical, walk away from it when you start bighting your lower lip, and as ive said earlier take pictures. :savewave:
 
Johnny,

I agree that it's not rocket science, but there are LOTS of ways to screw up. DOCUMENT EVERYTHING! as you disassemble. Photos, labelled bags, notes, etc.

I got my new synchro rings, etc. from A-H Spares in England. Working on a hunch, I carefully cross-hatched the working surfaces of the synchro rings, using a Dremel Tool and a thin circular metal-cutting blade. This is the internal (female) conical surface. It worked: I have the best synchros EVER. I have no doubt that the cross-hatching did the trick.

Anybody else ever done this??
 
:yesnod: Thanks Anthony, you are so right on. It's easy to get carried away with enthusiasm as the parts seem to fly off the transmission (pun intended), only to wonder later "now how did this go in again". My car also is a '63 BJ7 and when I bought the car I was told the 1st gear was bad. Not until now do I realize that what I discovered is that the 1st gear set only has about 50% of the teeth left. Mind you none were broke, but just chewed up! Which also means the lay gear teeth are also chewed up, and the reverse gear also is chewed up. So now I wonder what could of caused this? So you might be right, maybe the synchros or shift forks are off. Now I know why it costs about $2K to rebuild a Healey transmission, or why others have opted for a Toyota 5 speed conversion.

Again, thanks for your help.
 
BobFrisby said:
Johnny,...
I got my new synchro rings, etc. from A-H Spares in England. Working on a hunch, I carefully cross-hatched the working surfaces of the synchro rings, using a Dremel Tool and a thin circular metal-cutting blade. This is the internal (female) conical surface. It worked: I have the best synchros EVER. I have no doubt that the cross-hatching did the trick.

Anybody else ever done this??
Click to expand...

Thanks for responding Bob. Did you take pictures of how you did this, sort of a before and after photo? Maybe you can explain how this would help?

Thanks again
 
johnny, ive never heard of this being done but the
"grooves" would allow a greater amount of lubricaton between the male conical face of the gear and the female side of the synco, simple yet elegant! :yesnod:
 
Johnny,

Well, the synchros work by the friction between the synchro-ring surface (the one I cross-hatched) and the surface that it mates to when shifting. With all that slippery oil, it's amazing that this works at all! I figure that the cross-hatch grooves allow oil to escape from between the mating surfaces. This would encourage closer metal-to-metal contact, thus increasing friction and making the synchros more effective.

That's my theory, and I'm sticking with it.

I'm afraid that I didn't take any pictures, but the exact pattern of cross-hatching should not be critical.
 
I think what causes the downfall of the gearbox are the layshaft bearings (okay, that and rough handling of 1st gear). As they and the layshaft wear, the laygear is allowed to get further away from the 1st gear cog, so that the load is applied more to the middle and ends of the teeth, instead of closer to the root.

EVERY Healey box I've taken apart (as well as the early MGB_3-sync type) has had the layshaft worn down, allowing the laygear to move away from the 3rd motion shaft.

I would consider periodical replacement of the layshaft needle rollers a maintenencae item. It would save big money in the long run.
 
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