Originally Posted by Big Al's
I want to make sure my thinking is straight. You have written the transmission gear ratios as a decimal per Astro:
1st gear 4.03 to 1
2nd gear 2.73 to 1
3rd gear 1.49 to 1
4th gear 1.00 to 1
5th gear 0.72 to 1
Does that mean in 5th gear that the out put of the transmission will see about a 25% over drive over 1 to 1 (direct drive) of fourth gear? I get confused with the gear ratio and what it means.
I bought new, in 1986, and special ordered a 4.3 Astro with a T-5. After many miles, a transmission reb. and my teenage son rolling/totaling it, I bought back the salvage just to keep the T-5. This transmission I still have stored, with only a few miles on it! I junked the rest of the Van for at least double what the salvage was and still was able to keep the T-5!
Yes, the shift from 4th gear to 5th will cause a 28% drop in RPMs. That's a nice drop and matches well with a rear diff of 3.42 up to 4.10 in my opinion (3.73 rear diff is ideal IMO).

The T5 gears I mentioned above were in a T5 I pulled from a 1989 4 cylinder Astro van at the salvage yard. Not all Astro vans will have the same 1st and 2nd gear but they seem to all have a 0.72 or 0.73 5th gear according to THE BRITISH V8 WEBSITE chart (however I find that it is frequently wrong). The best way to check the gearing is to turn the shafts yourself. This LINK will take you to my T5 page which shows how to calculate the gears in 5 minutes (with a helper). Please visit my other T5 PAGES for lots of T5 reading.

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