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87 b150 rear questions

1.4K views 11 replies 7 participants last post by  MIRADAMEGACAB  
#1 ·
I had neglected a bunch of rear end symptoms for years culminating in the rear seizing, the drive shaft spinning the nut loose, then dropping on the highway (that was fun).

I hastily bought a junkyard rear with little regard for VIN info or stampings or anything. My intention was to use the junkyard rear as a core, and rebuild it (since my wrecked rear was likely unrebuildable at that point), and install gears of the original ratio, or a more optimal ratio (was having a trans problem that was easily remidied with a $600 rebuild, but at the time considered it may have been a lost cause and entertained switching to an AOD or manual, if I was shelling out cash for a trans anyway)

Since then, the van had been taken off the road for years. Just this summer, I did 10 years worth of catch up repairs on the motor, emissions, fuel system, brakes and exhaust.

As I am driving it again, I am reminded that the gear ratio of the junkyard rear is just plain wrong.

Top speed is around 65-70 (per the speedo, which is also wrong, of course), v.s. 80-85 with the old rear (not in nearly as good running order as it is now--it's a /6 1bbl, btw)

The JY rear is off of a larger V8 van (b250, 15 passenger, I think) with larger brakes, etc. It's starting to make noises (moreover the motor is now quiet enough for me to hear--mostly gear mesh noise, but still...)

I'm looking to reseal the rear, check the bearings and change the gears to the original ratio for the van.

How do I identify the JY rear?

How do I decode my VIN to find the original ratio apart from asking a dealer? (my local Dodge dealer is not so thrilled to hear from the likes of me. Where I live nobody drives anything over 5 years old, and the parts department seems to exist just to provide repair parts to thier own service dept, and replacement parts to body shops. They would gladly do without my $100 worth of business every three years or so.)

Any info is greatly appreciated.
 
#2 ·
10 cover bolts and it it the 8 3/8 rear, commonly called the 8 1/4
12 cover bolts and it is the 9 1/4 rear.

The ratio will be stamped onto the ring, or might even be stamped onto a tag under one of the cover bolts.

When I was dealing with rear end woes, I found a good website with specific instructions on the 8 3/8. The 9 1/4 is similar, just larger. I no longer have it bookmarked.

Google it.
 
#3 ·
The VIN won't tell you the rear ratio. Do you still have the old rear? The ring-gear will have the ratio stamped on it. There may be an equipment label stuck to the underside of the hood that may give you that info as well.
 
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#5 ·
On rear axle noise I found on my van that the tires needed to be balanced & rotated. Might try having that done.
 
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#7 ·
ok.

It's an 8-1/4" (8-3/8")

That's what the original was, too.

Really starting to regret not pulling the gears from the original (actually no, the pinion was destroyed and the ring lost some teeth as I recall--nevermind--I do recall the tag from the old rear had no ratio on it, just a Mopar # that the dealer could not decipher.)

All tags and stickers off the van yielded nothing.

The VIN really has no info? (I'm guessing a dealer matching a 'build sheet' to the VIN is not a likelihood.)

What if I work backwards--i.e. i.d. trans and speedo gear? Wouldn't specific combinations work with only one rear rartio?
 
#8 ·
The VIN really has no info? (I'm guessing a dealer matching a 'build sheet' to the VIN is not a likelihood.)

What if I work backwards--i.e. i.d. trans and speedo gear? Wouldn't specific combinations work with only one rear rartio?
The VIN build sheet for my van does tell me which axle is in it and what gear ratio. But here is a problem my build sheet say 3.21, my understanding of Dodges are that they only built the 3.24 as the smallest ratios. Also the sheet said I had a 117 Amp Alternator yet it was only 90 amps and the option was 135 amps, never have seen the 117 amp one. There are other descrepinsies in the sheet. So the sheet may or may not help you.

The speedo gear will not help for you can switch out the gears inorder to match the different size tires you can put on the rims.
 
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#10 ·
I have never heard of a 3.24... It's like a prime number.
In the 8-1/4 rears I believe that 3.21 is the lowest # truck/van axle made. They also made 3.55 and 3.92's in the late 80's.
My '78 van had a /6 and a 3.55 rear whith would top out in the 80mph range with 215/75-15 tires.
I put a 2.71 ring and pinion from a car in it and it would go just over 90 with 255/60-15 tires... (The /6 just runs out of breath. Mine was an auto had the 2bbl carb.)
Bottom line I would guess you have 3.92 gears or 3.55's and a really tired engine.
 
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#11 ·
I have never heard of a 3.24... It's like a prime number.
In the 8-1/4 rears I believe that 3.21 is the lowest # truck/van axle made.

Further research and found that the 3.24:1 is a misqoute, from where I got it I don't know. But that still does not explain other descrepincies in the build sheet. One other descprency is it says that I have a 4 speed OD tranny, it is and always has had a 3 speed auto. I have not seen anything with the 3.21:1 haveing been mated to an OD tranny.

My point is that the build sheets are usefull but not gospel.
 
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