I have the 1975 B210 120Y model with an A15 engine and a 4-forward gearbox. My diff is really damaged, and I want to replace it. I am getting the original B210 complete back end as well as the complete B310 back end to buy. The problem is I don't know which one to buy. I know that the original B210 will work, but since I have an A15 engine the diff may give out again. Does anyone know if the B310 complete back end will work on the B210 120Y or will I have to do some modifications? Secondly I don't know if the B310 model came with coil spring or spring leaf. If anyone can help me I'll really appreciate it. Thanks.

tHE 310 HAS REAR COIL SRINGS BET THE HEAD SOULD FIT YOUR 210 HOUSING

B210 (US models) and B310 use the same differential -- the H150. It's strong enough, Nissan used it with the A15. Some Aussie B210s had a stronger Borg Warner differential.

The B310 assembly (axles and everything) won't bolt into the B210 because it uses coil springs.

Your biggest problem may be the 4-speed. Most have a steep first gear, which means more torque sent to the back. Use a 5-speed and it'll be easier on the differential.

Thanks, but in my country it is very hard to get the 5-forward, I've been looking for it for a while, but no luck yet. Ok if I use the B310 back end, how will I cater for the coil springs or can the spring leaf on the B210 work on it?

When RMSPOWER writes "backend" i assume that he really means "rear axle assembly" & not the rear 25% of the vehicle body that this term often describes.
I also assume that when A14force writes "head", he actually means, "third member", or differential assembly", "diff center", or just "diff", & not cylinder head, or "head" as it is more commonly known.

I don't want to make waves, but these components have industry standard names, or descriptions, to avoid confusion, & using them provides a clear indication of what you are talking about.

ddgonzal
By steep first gear, i presume that you mean that in a four speed, the first gear ratio is closer to second gear ratio than the five speeds first gear ratio. That has cartainly been my experience anyway, but i dissagree with your comment that the taller first gear in the four speed is harder on the diff.

By way of illustration, lets go to the ridiculous, & just imagine using third gear as a takeoff gear. This is certainly a lot higher, or steeper than either of the first gears we have mentioned.
The component that will suffer mostly will be the clutch, & not the diferential.

The greater REDUCTION offered by the lower first gear of the five speed means greater torque MULTIPLICATION to the diff. The clutch is fine as it must handle engine output only, with less resistance to inertia due to the increased torque available at the pinion.
In a high performance application, the lower first gear ratio of the five speed will test the limits of diff strength more than the "steeper" one in the four speed.

In normal driving, the lower ratio of the five speed makes it easier on the clutch & the engine as the engine does not need to develop as much power to generate the desired torque at the pinion, & the clutch needs only to handle the reduced engine power at take off. Remember, i said "for normal driving"
Chris

Hello all , yes Dodgeman is right . By head I mean differential centre ( should be the same as 210) RMSPOWER, what country are you in? Filling in all your details makes helping you easyer.

Thanks Dodgeman, and yes I mean the rear axle assembly. I am using the vehicle for normal everday driving so I guess the 4-forward will work. What can I do to take off the strain from the clutch an engine? I'm from Trinidad and the 5-forward is really hard to fine, as a matter of fact a lot of mechanical parts are becoming difficult to fine in my country. But I'm determine to keep my Datsun and have it going, even if it means using other parts. I've been looking for the rear axle assembly for a while now and I finally found a place that have both the complete rear axle assembly for the B210 and the B310, and they are both used from Japan. My only query is which one to buy, because the B210 is spring leaf and the B310 is coil spring. If I buy the B310 will it work up on my B210. what is your recommendation since I'm running an A15 engine.

Dodgeman - I understood your comment but I believe you've got some confusing terms throughout the post.

Quote:

A higher gear would be a numerically lower gear by most people's definition. A steeper gear would be a numerically higher higher gear by most people's definition... at least in the U.S. not sure how it works 'down under' (can't wait to hear the ridicule for using that phrase but I had to do it ).

Coincidentally 56A 4-speed boxes, which I may be assuming too much, but I figure that's what he's got have a relatively steeper 3.757 1st gear ratio to an overdrive 60A box with a 3.513 1st gear ratio. A dogleg box, however won't net you a gain in either direction with the same 3.757 1st and an option 1 would be you're best bet with a 2.276 1st. Since 5-speeds are scarce, however, you could maybe score a 60A 4-speed which should have a 3.513 1st.

2332owner, you clarified what I was trying to say. I was thinking of the B110's 56 4-speed versus the B310's 60a 5-speed. I figured it would open some discusion because there are various gearsets.

Dodgeman, you are correct. However, by "steeper" we say for example that 4.11 is "steeper" than 3.90 gears.

I usually avoid "higher" and "lower" terms because a higher gearshift number (i.e. "2th gear") is actually a lower numeric number than 1st gear -- as you explained already.

Quote:No.