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Differential housing question

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I decided to pull the chunk out of the parts car I have here which is a RB car. I also have a 3.70 chunk in the trunk. The 3.70 housing is cast iron and the 3.90 that I pulled out is aluminum. Any advantages to either one (just the housing and carrier, not the ratio)?
 
Aluminum is lighter ?
cast iron stronger ?
Aluminum will warp at gasket edges easier?
I really don't know why they are different or the advantage for a light weight low horsepower car as the MG Midget
 
Well, stupid me, it's NOT for a Midget! Upon closer inspection, the whole unit is larger. It must be for a B. The guy would buy anything in the JY that was for a MG. I did have some other B stuff in the trunk w/ the diff, but not allot.

So, the aluminum one haS A DEFINATE advantage....it'll fit. :wall:


Is a 3.70 for a B worth anything?
 
kellysguy said:
So, the aluminum one haS A DEFINATE advantage....it'll fit. :wall:
Click to expand...

decision made.

so, to reiterate a question from before, I have a whine in my diff - I've replaced the seal, is there anything I can do?
 
Constant whine, or on decel? Bearing preload might not be correct.

Did it whine before?
 
I don't really know if it wined before - it doesn't really wine on decel. could you please explain preload to me.
 
Preload is measure by the amount of torque it takes to turn the pinion gear (by itself, actually a measure of resistance.) The more you tighten the pinion nut, the more the bearings are loaded and the harder it is to turn. Using a flex type torque wrench on the pinion nut, you would turn the free pinion by itself and see how much the wrench reads. That is the measure of preload. if you need more load, tighten the nut more; less, back it off.


A whine is usually associated w/ gear wear of lash.

So, if it didn't whine before, and you changed the seal, I'd say you might have a preload issue (unless it ran dry enough to hurt the gears and cause the noise.) I just read some threads on another site talking about a whine on decel attributed to improper preload.

If it did whine before, the what you did has nothing to do with it.

Pinion nut is torqued to 135-140 ftlbs, don't use an impact. You won't be able to measure true preload w/ it still in the car. Just torque it to around 135-140. You're supposed to change the crush sleeve in the diff everytime you take the pinion nut off, but it's no longer avalible. The crush sleeve goes b/w the inner and outter pinion bearings and is supposed to give (crush) @ 140 ft lbs to give the bearings the proper amount of preload. It's supposed to only do this once.

My BL manula says to have 11-13 FTLBS of preload, which really seems like allot as most other cars I've seen call for inlbs b/w 11-29m, and I'm talking big stuff.

I'm starting to trust this book less and less each time I use it.
 
IT is torqued to at least 135-140 I do know that. Although I can check again if necessary. Part of the problem is that I don't know if there was whine before as I did the seal while rebuilding the car - had never driven it before. It's not a large whine, it's just a little annoying.
 
Should not be any noticeable noise.
 
Jp,
rear ends are a little tricky- but if your careful and read up a little on them they are not black magic. What has most likely happened is that when you re-torqued the pinion nut you shifted it a little bit and now it may be causing the whine. I believe you when you say you torqued the nut to 140 range. Did you make a flange tool or something? (and grow really big arms?)If you torque against a crush washer to the same torque twice then you have changed the position of the pinion gear. The cure is to re-shim the crown wheel to realign the gap and contact patch between the two (or find a crush washer). There are shims made for doing this. It is not difficult, just time consuming making a lot of measurements, taking it apart and putting it back together several times. Cleanliness is a must during this procedure. good news is you can drive a very long ways before you would do really serious damage. But eventually.....

m
 
First time I made a flange tool, second time we tightened on the ground - (First time the seal was wrong) so it did run empty or more likely close to it some. Not much though as it was during break in period. where can I read on this? I'll check the manuals shortly
 
thanks - so, this doesn't seem like something I can with the diff on the car - is this correct?
 
that would be correct JP. Have you been following the "crush sleeve " thread?

m
 
JP, pull the seal and front bearing, put in shim and put it back together like Dave said. You can do it in the car.
 
OK - yes, I have been following both conversations. Here's what I've decided. First of all, there is apparently an LBC guy on the north end of Toronto who wasn't getting enough LBC business to make a living so went into transmissions. before I do anything I will let him take a listen.

However, where do I get me a shim if I need to go that route?
 
A regular 2 foot pipe wrench makes a pretty good flange wrench. If you take it apart, remember where the shims go. Also, use some prussian blue on the gears to check the mesh. Getting the pinion depth right can be a bugger but the backlash is not too bad a job.
 
Think not, as least I would not try.
 
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