The Oldsmobile Connection

[tree2167]

HI everybody

Just got i quick question. i blew the head gasket on my 81 olds delta 88 royale. it had the olds 307 in it. I am doing a engine swap to a rebuilt chevy 307 but i dont know what my rear end gearing from the factory was. if anyone knows i would appreciate the info.

[andrewk]

tree2167 wrote: HI everybody

Just got i quick question. i blew the head gasket on my 81 olds delta 88 royale. it had the olds 307 in it. I am doing a engine swap to a rebuilt chevy 307 but i dont know what my rear end gearing from the factory was. if anyone knows i would appreciate the info.

There were several options from the factory. The easiest way to figure approximate gear ratio is to make an index mark on one wheel, and turn the pinion until the tire makes one complete revolution. The number of times you have to turn the pinion is your gear ratio. E.G. If you turn the pinion 3 times to every 1 revolution of the wheel, your rear end ratio is 3.00:1. The numbers probably won't be quite that nice though.

Good luck with the swap-

[88 Coupe]

Hi tree2167,

Welcome to TOC.

A little clarification is in order:

andrewk wrote: ........ make an index mark on one wheel ........
Unless it's an "Anti-Spin" differential (set up to factory specs) both tires would need to be marked.

Quote: ........ turn the pinion until the tire makes one complete revolution ........
Make that both tires, in the same direction.

Quote: ........ If you turn the pinion 3 times to every 1 revolution of the wheel, your rear end ratio is 3.00:1 ........
If you only turned one wheel, the ratio would be 6.00:1

Quote: ........ The numbers probably won't be quite that nice ........
For a more accurate check, you could mark the driveshaft/pinion and turn both wheels/tires 10 times. 25½ driveshaft (pinion) revolutions would indicate a 2.56:1 gear.

Quote: ........ Good luck with the swap-
Good luck with that Chev engine.

Norm

[andrewk]

Thanks for the clarification Norm.