What rear end ratios do our vans have?

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

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

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

,,,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

Love the knowledge on this site!

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

,,,,,,,,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,,,,,,,,

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.
Chaz

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

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.

One can only tell by doing what was suggested with marking or counting the teeth on the tow gears. Mine has a 3.08 (I had installed) and a 10 bolt. These are so old I would not assume many parts have been swapped. Incidentally, my pretty stock 65 with the 196, maybe a 230 runs down the highway without much roar or overheating. However, 1st gear is long. Could almost stay in 1st gear around town.

ChevyVanMan1
I sent you a question in a PM

Thanks for sharing. This will come in handy