Transmission swap - 79 G5

[wirespokes]

Coasting down my driveway I noticed a knock, just a light clunk, about every ten or fifteen feet.

On the centerstand rotating the rear wheel I can't reproduce the knock. I think it's coming from the transmission - it's hard to say. Just guessing.

Usually I can come up with a good guess what might be going on, but in this case I haven't a clue.

Any idea what it might be?

So I'm looking at possibly tearing into the transmission. I do have a transmission from a 97 Cali and wonder if it'll fit in the 79 G5.

What's the newest trans I can fit into the earlier tonti big blocks?

[John A]

Could be u joint and its carrier bearing.

[Chuck in Indiana]

Could be u joint and its carrier bearing.

Agreed. You are going to have to have it out anyway, start doing that, and maybe you'll find your problem.

[acogoff]

     To my mind your transmission turns way more than one turn for every ten feet. Your wheels turn the slowest of the moving parts.
 I would start there as in wheel bearing or a brake pad doing something funky before you start getting into the serious disassembly.
 Keep us posted.

[Antietam Classic Cycle]

The '97 California transmission will fit fine, but two things to keep in mind: 1) the '97 used an 8/33 rear drive, so the speedometer drive in the transmission is a different ratio to suit. This will make the speedometer way off. 2) the '97 transmission will have plastic-caged input and output shaft bearings, which may fail.

[guzzisteve]

Could be u joint and its carrier bearing.

The 97 trans will fit, all the way to 2014 trans 5 speed.  I also agree on a ujoint, easy swingarm pull.

[wirespokes]

U Joint makes the most sense to me too. Have any of you rebuilt them?

Thanks for the heads up on the speedo drive, Charlie. Do the gears need to be swapped as a set?

The box has something like 70K on it, but don't recall if it was gone through or not.

[Antietam Classic Cycle]

Thanks for the heads up on the speedo drive, Charlie. Do the gears need to be swapped as a set?

They should be.

[wirespokes]

Even though the noise seemed to come from the transmission, u-joint made the most sense.

Had some time today, so pulled the wheel, swingarm and u joint. And glad I did!!

It's scary what I found - one of the bearing caps was half chewed through and gnawed away at the carrier as well. Junk! 

Seeing that reminded me that I'd noticed a sort of 'straining' at speeds over 80. I thought something was a slight bit out of balance or something. Or maybe the ignition was a little weak...

Haven't done a test ride yet, but I'm sure that was it. Considering how far gone it was, I'm surprised it took coasting down the driveway to hear that slight knock every seven or eight feet. And even then it didn't register as something awful. I sure didn't notice anything in normal riding. Now that's scary! Man, I sure came close to a catastrophic failure on that one! Coulda been messy - especially since I like going fast sometimes...

[guzzisteve]

I had one fail going 70 & vibration was terrible, slowing up it locked up when I got in 1st. Cocked & put a hole in the cavity it spins in

You dodged the bullet this time, listening to you bike.

[wirespokes]

Sounds like things could have been a lot worse for you too. What did you do about the hole in the swingarm? Straighten the metal and solder or weld it up?

Just got back from a test ride. Lots smoother!

One of the reasons I was considering the transmission was because it was being difficult shifting. But, funny thing, with a good ujoint, it shifts like a dream.

[guzzisteve]

I break drivetrain parts, it's what happens when you use your throttle hand. In my LeMans owners manual it says to use to Maximum Permissible Limits

[wirespokes]

I break drivetrain parts, it's what happens when you use your throttle hand. In my LeMans owners manual it says to use to Maximum Permissible Limits

Hahaha

That's not what I recall. More along the line of "don't baby the machine, it's hard on it."

I don't believe going fast is hard on the driveline, but sudden acceleration and deceleration are.