Ironhead Trans/Year Interchangeability Question

[ferretface]

Originally Posted by mct496

You dont wanna wait till they break the cases end up busted alot of times

Thanks for the caralog numbers!

I agree. Is there a common indicator of impending disaster??? Clunking noise, shuddering, false neutral, anything like that???

[IronMick]

It happened to mine right out of the blue. Leaving an intersection, not going hard, 1st OK, 2nd, maybe OK, 3rd - I had to coast off the road. Had no idea. No problems for a few years prior. Just happened. Walked it home.

[doodah man]

close 4th
https://www.jpcycles.com/product/630...&totalResult=1
a little cheaper on amazon
https://www.amazon.com/s?k=andrews+2...ref=nb_sb_noss

exploders
https://www.jpcycles.com/product/620...shaft-2nd-gear.
$84 on amazon
and
https://www.jpcycles.com/product/620...shaft-3rd-gear
$73 on amazon

[mct496]

I can understand wanting to keep down time to a minimum and while trapdoors are generally interchangeable(sometimes bolt holes require a little egging out for alignment purposes) any time you have the original trapdoor your gonna wanna use that over any other door

[ferretface]

I would like to thank all of you guys for your help and suggestions. You've given me a lot to think about.

It's been 45 years since I've done any transmission work, and that was limited to replacing synchro rings in Triumph and Muncie 4-speeds. Very little [none?] shimming required. It was my hope that just replacing the entire unit as an assembly would be sufficient, with the 3rd mainshaft and 2nd countershaft gears replaced with Andrews parts.

From comments here and reading threads and the FSM, rebuilding/shimming it looks like a long tedious procedure. I'm still mulling over whether to get a 2nd complete transmission. There's a big cycle swap meet next July at the Mid-Ohio Sports Car Course. I've been planning to attend. I'm thinking I'll get the two Andrews gears first and maybe the 4th main drive set later. And look for a reasonably priced complete trans at the swap meet.

I still have several items to attend to on the Sportster this winter. I'm thinking I'll take it easy on the cycle this coming summer and plan on the trans upgrade next winter.

Or I'll be selling numerous parts in the For Sale forum and junking a shattered crankcase.

[doodah man]

Do not fear a trans rebuild. It’s not nearly as hard as it appears. Careful observation and a little measuring is about it. Oh, and a fistful of dollars

[ferretface]

I was offered a 'complete' Ironhead trans that had been sitting for years. Many years. It was caked with sticky old dehydrated oil. Story is that it came with a basket full of parts. Shop owner says look it over; see what I think.

Has the notch, trapdoor casting is 34846-76



I washed it off with solvent, teeth have some nicks but appears to have all the teeth and dogs.



Got out my parts book, FSM, and Clymer manual and stripped it down.



Curiously, it has an Andrews 3rd mainshaft gear. The gear has the ratio rather than the part number as other Andrews gears have.



So far I haven't committed to buying it. It all looks OK but not perfect. But I do have one serious concern: I can't seem to get it to work correctly on the bench.

In Neutral, the gears and shafts all spin freely, but the input and output shafts are locked. Shouldn't they be disconnected in neutral??? That is, turn independently???

And in 1st, 2nd, and 4th, the gears/shafts lock up and won't rotate, but they can be rocked backed & forth maybe an eighth of a turn. I've compared the gear positions with the 'flow chart' illustrations in the FSM and they all match.

3rd gear is the only gear that seems to work correctly. Input and output turn freely but not the same - It's definitely stepping the gear ratio down (or up, whatever).

I have it mounted on a steel angle fixture. Is there some trick to getting the gears to engage correctly while bench testing???

3rd mainshaft gear has been replaced, also one of the shift forks looks different (kind of a gold color) so that may have been replaced.

Even if I don't buy it, I'd like to get it 'working' correctly for practice when I pull mine out. The shop owner gets it cleaned; we both win.

So...What is the trick/problem with this gearset???

[paulc]

Originally Posted by ferretface

.......From comments here and reading threads and the FSM, rebuilding/shimming it looks like a long tedious procedure........
....... I'm still mulling over whether to get a 2nd complete transmission. .....
...... I'm thinking I'll get the two Andrews gears first and maybe the 4th main drive set later...............

It is long and tedious but worth the effort. I did a trans for the first time (with a lot of help from this forum) on my 76 last year. It wasn't easy to get my head around it but got there in the end. It's a real sense of achievement getting it done and a buzz when you ride it and it shifts properly.

A 2nd trans is a good idea, looks like you've found one now.

The Andrews 4th gear change is well worth it, the difference is very noticeable. My project bike has an all new Andrews trans (shafts and gears) in it I'm told. It's a standard ratio Andrews 4th though unfortunately. I like the change of 4th on my 76 enough that I will change out the new 4th on the project bike before I get it running.

On the bench shifting can be less smooth than in the bike even if everything is ok. The shaft ends aren't held properly at both ends on the bench which can effect things. You should be able to shift through ok though. I found that the top hats shifting could affect things on the bench. Also the shifter shaft moving around - it should be tight in the trapdoor (press fit from factory) but mine was loose so I used green loctite on it and things were better afterwards (see my trans thread in the stickies if you have this issue)
Problems in the tower can cause bench issues too, I had problems with springs that needed changing out.
I'm a rookie with trans work but thought a few pointers from what I learnt last year might help.
Paul

[ferretface]

Originally Posted by paulc

A 2nd trans is a good idea, looks like you've found one now.

I'm not sure this is a 'keeper'. There's no big chips in the gear teeth, but there are numerous small nicks.

The Andrews 4th gear change is well worth it, the difference is very noticeable.

I'm still on the fence about that.

On the bench shifting can be less smooth than in the bike even if everything is ok. The shaft ends aren't held properly at both ends on the bench which can effect things. You should be able to shift through ok though.

That I can't do. Only 3rd behaves like I think it should.

I found that the top hats shifting could affect things on the bench. Also the shifter shaft moving around - it should be tight in the trapdoor (press fit from factory) but mine was loose so I used green loctite on it and things were better afterwards (see my trans thread in the stickies if you have this issue)

All the shafts are loose in this basket case trans. The shifter shaft isn't too loose, but I can pull it out easily, even rotate it with two fingers. I don't know what you mean by 'top hat'. ???

Problems in the tower can cause bench issues too, I had problems with springs that needed changing out.
I'm a rookie with trans work but thought a few pointers from what I learnt last year might help.
Paul

Tower??? That's the shifter???

I am always looking for tips on what I'm doing, since I have no clue on what I should be looking for. Thanks for your comments!

[paulc]

This is what I mean by the tower:



No 40 in this image:



These are top hats:



No 28 in the drawing from the parts manual.

Have a read of my trans thread for a newbies eye view of things. Reading and assembling/disaasembling over and over is how to get it to make sense. Lot of members on here are very experienced with IH trans so ask away when you get stuck.
Paul