Rear End Gear Change Help

Hello, I have been trying to obtain first hand experience with those who changed the ratio in the rear end gears. ( Sorry if my wording is not right, I am NOT mechanical!


Questions in order.

# 1.What ratio is best to lower it as much as possible, but not where it doesn't drive properly?

# 2. Where do you purchase these parts on-line or store?

# 3. What other parts may need to be replaced for this job to be done?

# 4. Are there any drawbacks to doing this?

More info for you possible questions. It is a 12 bolt. I do not know what gear ratio it is now, I am doing this because my engine revs very very high at 50 miles an hour and eats 11 miles per gallon, something is not right, this could change that.



Thank you

William

for my 2 cents & having been a mechanic now for 50+ years. The rear end gearset change is still something -I dont tackle!! Both gears must have the "Backlash set" and unless you have done this type work prior?? Leave it to the guys tha do! New bearings - gearset (new) crush sleve & shims and seals to be done right- for parts. Then if ur dealing with a posi setup-likely new clutches in there . Lots to do & having to learn all?? look in ur craigslist locally for someone thats does this.  

Summit has kits for most things. If it is a stock van axle it will or should be a 3:73 or 4:11. Food for thought, an overdrive trans can make these ratios livable.

Hi William.

The 12 bolt axles usually had 3.73 gears in the rear.   The 10 bolt axles usually had 3.36 gears.  This is all assuming nobody has swapped in different gears.  

The 12 bolt axles are a 'truck' 12 bolt.  They take 'truck' 12 bolt gears and related parts.  The 10 bolt axles are a chevy 8.2 rear axle (not to be confused with a BOP 8.2).  

If you are 'not mechanical', you should not even consider trying to perform a gear change yourself.  Setting up gears is an advanced job that requires special tools and knowledge.  For this reason, expect to pay serious money at a shop for labor to have this done.  When I had my gears setup in my '64 wikivan, I had it done at a local 4x4 shop.  It cost about $500 in labor plus parts.

The least expensive route is to find a 3.36 geared 10 bolt rear axle from somebody and swap it into your van.   Another option is what Digz suggested, consider a 200-4r transmission swap.  that will give you an overdrive, and will be a perfect match for the 3.73 gears.

A cheap alternative that will help at least for the time being is to score some 15" wheels, or maybe you can find some vintage big n little mags or maybe some cragars (14's on the front, 15's out back), and run some taller tires in the back.  For example, if you currently have 205/70r14 (25.4" tall), and swap to 275/60r15 (28" tall), your 3.73 gears will now be effectively 3.38 gears, and it will reduce your engines revs when traveling at highway speeds just like a gear change would...  also your van will look cool with a hot rod raked stance!  Look on craigslist for deals on cool wheels.  You need 5 on 4&3/4" bolt pattern.

A friendly VV forum tip:  edit your location and add your CITY.  'Kansas' is a big area, there might be someone near you who can help you or has parts, or maybe has a set of some sweet old rims int eh back of their shop, or knows of a local wrecking yard with a van in it, but if you are vague and secretive about your location, you'll never know...  ?    

I agree with Kookykrispy..!!!.. I went from a 411 gear to 373 and it was about $1,000 for parts and labor at the 4x4 shop (New Bearings also) find some 15x8 inch rimes for the rear and go with a wide 275/60/15 or narower same highth 235/70/15 it will look much better and will  be much cheaper than changeing gears or looking for another good 48 year old rear end that does not need to be gone through (Rebuilt) is going to be next to impossible..Personally I would just live with it or put some taller tires on it these's vans were not built for good gas milage....JMO..  ..

The van axle bearings are not truck. They are the same size as the 10 bolts. 1.44 or something like that.

Digz wrote:The van axle bearings are not truck. They are the same size as the 10 bolts. 1.44 or something like that.

I think the 10 & 12 Bolt Rears in our Van's Have the same bearings as the GM 60's Car's..Nova, Camaro ,Chevells..I know the 12 bolt and the 10 bolt in both my 3rd Gens look like they have bigger housings and are much wider...The Rear End in my Early Van looks Identical to the one I had in my 1966 Chevy 2 Nova although I never measured it...  .

I ordered the "kit" for a 12 bolt truck when I first tore into mine. You could have played ring toss with the bearings on the axle. The center bearings and such were right. Needed the repair bearings anyway so it wasn't a big deal. The splines on the center end are different from 10 to 12.

Good info to know. Thanks guys. So, the axles bearings are car type, and so are the brakes, backing plates, brake hardware, etc. 12 bolt guts use 'truck 12 bolt' parts, not to be confused with 'car' 12 bolt.

Don't know where in Kansas you are, but here's an ad for some slot mags in KCMO

http://kansascity.craigslist.org/pts/4544217168.html