Possible to change gear ratio?

[Zogbert]

1972 C-10 with 250 and three on the tree.

At present it has 3.73 ratio. I'm getting the rear end rebuilt next week and am wondering if it's possible to have 3.42 or maybe 3.07 gears installed in the existing housing. I do mostly highway driving on a slightly hilly road. Truck is actually decent on fuel, but does rev fairly high at 60 mph.

Anyone out there with a 3.42 or 3.07 with a 250 and three speed? What's it like on the highway?

Is that particular gear swap even possible?

Thanks!

[kwmech]

With only a 250, you may need the gearing to get any type of feeling of power. I usually see them with 4.10 in them

[Zogbert]

I'm actually looking for highway cruising, not a feeling of power.

[Zogbert]

I've been reading it may not be possible to easily convert a 3.73 to a 3.42.

[kwmech]

Yeah, you'll need a different carrier and the gear set, new bearings and seals Not all that difficult, it's only money. However since cruising is your only concern you may want to look at a taller ratio. From the 3.73 to the 3.42 is less than a 10% change.. 9.4 to be exact

[jocko]

If you're just highway cruising and gonna keep the 6 cyl, a T5 is an easy swap and keeps the low end gearing and has o/d - will drop cruising rpm approx. 30%. If you can tell us your current tire diameter, we can tell you your cruising rpm at different speeds. Are you certain you have a 3.73? If you plan to swap in a V8 and/or lay the occasional rubber patch, then skip the T5 idea. It's a good trans, but not strong enough to be abused.

[Zogbert]

I'm thinking the T5 may be the best option. Thanks!

[67 chevelle]

t5 would be much better , you would keep your low end grunt and have another gear when you need it

[Zogbert]

I agree!
Posted via Mobile Device

[jocko]

Use this as a ref if you like, it's my old 66, but all the same principles apply.
http://67-72chevytrucks.com/vboard/s...d.php?t=482069