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What rear end ratios do our vans have?

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Skulptorchaz

Number of posts : 227
Location : So. East Indiana
Registration date : 2015-05-08

What rear end ratios do our vans have?

Post by Skulptorchaz on Fri Jan 27, 2017 8:32 pm

Hey gents,
I was wondering what the rear end ratio was in my van ('64 GMC w/194cu.in.) since I was planning a trany swap to a 700R4 and just curious.
I crawled under it and had a buddy spin the rear wheel while I counted the revs on the drive shaft............it didn't compute.
One rev on the wheel equaled one and about three quarter rev on the drive shaft. I thought that should tell me the ratio but, it can not be a 1.75 rear. What am I doing wrong? I asked a couple friends and they thought that was the way to do it as well.
Thanks!!
Chaz
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gfleduc

Number of posts : 130
Location : Kingwood Texas
Age : 62
Registration date : 2015-09-19

Rear Ratio

Post by gfleduc on Fri Jan 27, 2017 8:42 pm

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AzDon

Number of posts : 322
Location : Lake Havasu Az
Age : 61
Registration date : 2014-01-20

Re: What rear end ratios do our vans have?

Post by AzDon on Fri Jan 27, 2017 9:41 pm

Here is how to check:
Using a yellow parts crayon or wite out, make matching marks on the side of the yoke and diff housing....At the same time make a mark on one of the rear tires at the very bottom....
Have somebody roll the van SLOWLY forward for one exact complete rotation of the tire while you crouch down and watch how many times the mark on the yoke comes around....
Considering the ratios shown above, you should expect to see the yoke pass the mark at least three times and then either 1/3 more, 3/4 more or a fourth time past plus a tenth....

4.11 ratio means that the yoke turns 4.11 times for every full rotation of the wheels
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donivan65
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Number of posts : 11569
Location : San Diego, California
Registration date : 2008-05-12

Re: What rear end ratios do our vans have?

Post by donivan65 on Fri Jan 27, 2017 10:05 pm

10 bolt cover is a 3:36,,,,,,,12 bolts is a 3:73 0r 4:11
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donivan65
Governor
Governor

Number of posts : 11569
Location : San Diego, California
Registration date : 2008-05-12

Re: What rear end ratios do our vans have?

Post by donivan65 on Sat Jan 28, 2017 10:55 am

,,,now the right way to do it is take the cover off,,,,get rid of the old oil,,,,,,see if its a PosiTraction, look at the numbers stamped on the ring gear,,,,, a 3:36 says 11-37,,,,,,3:73 says 11-41,,,,,,4:11 says 9-37,,,,,,,,,,,,,,,peoples also put in a 3:08 which is a 12-37


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vanny
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Number of posts : 9590
Location : Ashburnham, MA
Age : 59
Registration date : 2012-09-22

Re: What rear end ratios do our vans have?

Post by vanny on Sat Jan 28, 2017 1:20 pm

Love the knowledge on this site! cheers Very Happy


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Skulptorchaz

Number of posts : 227
Location : So. East Indiana
Registration date : 2015-05-08

Re: What rear end ratios do our vans have?

Post by Skulptorchaz on Sat Jan 28, 2017 2:32 pm

You ain't wrong, Vanny!!!! I love all the "helpfulness". I'm hoping I can come up with some info to help others as well.
Chaz
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donivan65
Governor
Governor

Number of posts : 11569
Location : San Diego, California
Registration date : 2008-05-12

Re: What rear end ratios do our vans have?

Post by donivan65 on Sat Jan 28, 2017 3:45 pm

,,,,,,,,I myself like to hear about things that people do, or went, wrong,,,,,,,,its just as good as knowing how to do it right,,,,,probably could save someone time and money ,,,,,,,so dont be afraid to post answers,,,,,,,,they all count here,,,,,,,,
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Skulptorchaz

Number of posts : 227
Location : So. East Indiana
Registration date : 2015-05-08

Re: What rear end ratios do our vans have?

Post by Skulptorchaz on Wed Feb 01, 2017 6:13 am

I'm with ya Doni. I have some pix I am going to post in another thread about my belly pan build with radiator protector. I'm hoping I can be part of solutions, not just always having question marks behind my statements. Smile
Chaz
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gfleduc

Number of posts : 130
Location : Kingwood Texas
Age : 62
Registration date : 2015-09-19

Rear Axle ratios

Post by gfleduc on Thu Mar 29, 2018 2:41 am

donivan65 wrote:,,,now the right way to do it is take the cover off,,,,get rid of the old oil,,,,,,see if its a PosiTraction, look at the numbers stamped on the ring gear,,,,, a 3:36 says 11-37,,,,,,3:73 says 11-41,,,,,,4:11 says 9-37,,,,,,,,,,,,,,,peoples also put in a 3:08 which is a 12-37


That is great insight

I just read how the numbers work:
example shown in photo "11-37" code
11 is the pinion 37 is the ring; ring / pinion = 37/11 = 3.36
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gfleduc

Number of posts : 130
Location : Kingwood Texas
Age : 62
Registration date : 2015-09-19

Rear Axle code

Post by gfleduc on Thu Mar 29, 2018 2:48 am

The codes shown in post #2 - example H04. That manual said that the code was sampled on the differential carrier. Is the that stamped any place on the outside? I'll be danged if I could find anything on mine.

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