• Welcome to the new SAOCA website. Already a member? Simply click Log In/Sign Up up and to the right and use your same username and password from the old site. If you've forgotten your password, please send an email to membership@sunbeamalpine.org for assistance.

    If you're new here, click Log In/Sign Up and enter your information. We'll approve your account as quickly as possible, typically in about 24 hours. If it takes longer, you were probably caught in our spam/scam filter.

    Enjoy.

3.70 rear end

R

RootesRacer

Donation Time
DanR said:
RootsRacer,

I think I did it right.... 10 Revolutions of pinon 5 1/8 of wheel!
Click to expand...

If these are accurate numbers, your ratio is 3.89.


(10/5.125) * 2 = 3.902

NOTE: the 2 in the equation is becuase you have one wheel on the ground and the one in the air is going through the diff which doubles its speed compared to if the vehicle was driving and both wheels going the same speed.
 
Last edited:
M

mattinoz

Donation Time
I'm following this discussion with some interest as I am contemplating a differential replacement in the near future. I have a 3.8 diff teamed with an OD box but its very noisy. I note that several posters have mentioned the crown wheel and pinion set from Rootes spares in the Netherlands but no one has suggested the same kit from SS. So that begs the question, should the SS parts be avoided?
 
R

RootesRacer

Donation Time
mattinoz said:
I'm following this discussion with some interest as I am contemplating a differential replacement in the near future. I have a 3.8 diff teamed with an OD box but its very noisy. I note that several posters have mentioned the crown wheel and pinion set from Rootes spares in the Netherlands but no one has suggested the same kit from SS. So that begs the question, should the SS parts be avoided?
Click to expand...

Often the source of the noise is loose crown wheel bolts.

This can be remedied without replacement, but you do have to pull the axles.

I have ONLY heard of noise issues from new gear sets for the 3.70 and the only one selling new ones recently was rootes spares.
I have also seen original 3.70s built from the factory that were a bit noisy, so it may be a common problem to the 3.70 gearset design and not so much a new problem.
 
M

mattinoz

Donation Time
RootesRacer said:
Often the source of the noise is loose crown wheel bolts..
Click to expand...

That's interesting about the loose bolts. My noise is only on acceleration, noise almost disappears on de-acceleration. A local expert has listened to the sound and says that it is definitely a worn crown wheel and replacement is the only cure.

Any additional advice would be welcomed.
 
Jim E

Jim E

Donation Time
If you have not tightened your crown wheel bolts, replacement is a good idea and loctie is also a good idea, the bolts are loose often to the point you can turn them with your fingers. Is there an axle spline count difference to factor in here? when swapping center sections?
 
R

RootesRacer

Donation Time
Jim E said:
Is there an axle spline count difference to factor in here? when swapping center sections?
Click to expand...


Yes and no.

The center sections are compatible, provided the spider gears have the correct spline for the axles you have.
It is not terribly difficult to swap the the spider gears though.
 
George Coleman

George Coleman

Gold Level Sponsor
The 3.70 noise on my swap was a little iffy so I had it looked at twice and reset and still noise, nature of the gears I replaced ring and pinion.:cool:
 
T

Tom H

Platinum Level Sponsor
Dan, You have a 3.89 axle. Sorry I forgot to note that with just one wheel off the ground and turning you'll only see half the shaft rotation. I shoulda said turn the wheel 2 rotations and watch the shaft to see if turns more or less than 4 times, means slightly more or less than 4.00 :1 = 3.89 or 4.21

But your 10 x shaft rotatations worked well: 10 divided by 5.125 = 1.95. 1.95 times 2 is 3.90 . You have a 3.89 axle!

Tom

Posted before I saw the previous replies! But I still think it's easiest to turn the wheel (but 2 or 4 rotatations, not one!) and watch the shaft. 2 turns of the wheel will show the difference. One turn is too iffy as Dan found
 
Last edited:
65beam

65beam

Donation Time
rear end

I've never run into the factory 3.70 gears being noisy. they were used in the fastbacks and none of the cars I have had ever had a whine to them. I have heard many complaints about the quality of the parts from rootes spares. that could be one of the reasons they aren't being sold here in the states. they may be close to spec but just not spec'ed out close enough.
 
alpineracer

alpineracer

Diamond Level Sponsor
Tips on pulling axles

Good morning,
Jumping back into the game and have a '60 Alpine with rear end noise. In reading this thread it looks like I need to pull he axles and check crown wheel. Please offer tips on pulling axles. I did this 12 years ago, but have forgotten what Jarrid and Jan had told me....
 
R

RootesRacer

Donation Time
To do this you need to pull the axles and remove the center section.

After this, with the center section on a bench, you will be able to see if the bolts are loose. If so, removal of the bolts, will be required. The bolt washers will have been bent both around the crown wheel and the bolt head, locking it from removal (but didnt help it from getting loose). You will first need to get a chisel and flatten the washer away from the bolt head.
You are going to toss all the washers so no need to be gentle.

For reasambly, some say dont go with washers, some do.
I would go with washers, but only use grade 8 (hardened washers).
Grade 8 washers cannot be bent to lock the bolts as before, so you wont be doing this.
In each case (with and without washers) use a permanent locking loctite and NEW appropriate length grade 8 SHOULDER bolts.

Bearings also can make noise so check the inboard and outboard bearings too.
 
You must log in or register to reply here.
Top