7/33 rear diff. question

[Turin]

I'm looking for a 7/33 rear end for my Lemans SE project. Will an earlier 850T-Eldo deep sump hold up to a modified motor and ZD gearbox? Should I hold out for a later rear drive?  thanks.

[pete roper]

Yes it will but the eldos and 850T's used an 8/35 I believe. Also be very aware that early deep sump boxes had the 'Level Plug' much too low and using it as a guide will lead to torched gears.

Pete

[Turin]

Crap, never mind that then. With the tall first gear  I 'd like something lower, sidecar gearing would be ideal. I got this special 16 tooth primary gear with my project. Pete, If I put this back in the tranny, what kind of gearing would you recommend for the rear drive?

[pete roper]

Charlie will probably be a better source of info on ratios than me but really it depends where you are going to ride it?

If it's only going to be used for flogging around the traps then I'd go for the lowest gearing you can get, both primary and final drive. If you want to tour on it? Well, work out what works.

I thought the SE's as standard came with a 7/33? Have you actually confirmed the tooth count?

Pete

[Turin]

No touring. This thing is an ex AMA pro-thunder bike from the late '80s and early'90s. It'll end up being used for track days and back road shenanigans . It's a 92mm(transcontinental kit) bored big valve with high compression and a nasty cam (he said RR5?). Anyhow, I'd love your opinion Pete. 8/33 might be good if I want to go to Bonneville. I have that weird gear and don't know if I want to put it back in the tranny or not.

[pete roper]

Time to dig out Guzziology and go through the ratios. I have no idea of what was used in the SE box but I think it was a 'Stand Alone' unit with little in common with any of the earlier boxes.

Pete

[Antietam Classic Cycle]

Yes it will but the eldos and 850T's used an 8/35 I believe. Also be very aware that early deep sump boxes had the 'Level Plug' much too low and using it as a guide will lead to torched gears.

Pete

V700, some early Ambos, Eldo and T were 8/37 from the factory, Ambo and V7 Sport used 8/35. 7/33 would be 4.71:1 ratio, 8/37 is 4.625:1, so a bit lower.

The problem with using the earlier (drum-brake) rear drive on a later (disc-brake) swingarm is that the early pinion carrier flange is 2 mm thinner that the later one. So, you'd need to make a 2 mm thick shim to go between the pinion carrier and swingarm or rebuild the drive with the thicker flanged pinion carrier.

I would think a good (correct) 7/33 would be easier to find than an Eldo/T rear drive. Lots of buggered Eldo rear drives, sometimes hard to find a good one.

[Turin]

I'll keep looking. Everything on flea-bay seems to be 8/33, convert or loopframe.

[Antietam Classic Cycle]

I'll keep looking. Everything on flea-bay seems to be 8/33, convert or loopframe.

PM'ed you - one available cheap!

[Wayne Orwig]

Get 7/33 gears from MG Cycle.
Install and shim.
Ride.

[Turin]

E-mail sent! Thanks Charlie! one more hurdle jumped!

[Antietam Classic Cycle]

One of us should be making progress on their project...