Recommend Ed Rear end ratio with 250 and 3 speed

[bubbasimms]

Like the title says...I am rebuilding my rear end and wondering if maybe I shouldn't change the rear gears for today's world. Truck is a 69 short stepside, bags all the way around, drop spindles and blocks for the rear. Keeping the 250 and the 3 speed, added 71 front and rear for the 5 lugs, disc in front and power steering. Current gear is 3.73 but I remember it seemed a bit wound up at highway speeds. I will probably end up with a taller tire so that will help but should I maybe consider something like a 3.42 for the rear? It is very hilly here in the Ozarks, but will not be hauling or towing anything. Just cruising around.

Anyone have any real experience or suggestions? Keep the 3.73 and be content with 60-65 mph or change them and cruise more smoothly at 70-75?

[jocko]

All depends on what you want to do with your truck.

Want to cruise at comfortable rpm ONLY: yes, swap to a 3.42 or even a 3.07 (but I'd probably avoid that due to your hills)

Want to do burnouts ONLY? Don't change anything

Want to do burnouts AND cruise at comfortable rpm: O/D trans (T5, T56 (T5 maybe not so much if you're gonna do a lot of burnouts...))

I'd put your new tires on first, then see how you like it, it will reduce hwy rpm a little, but not much unless you go with a lot taller tire for some reason.
If you post the current tire diameter and the tire diameter you're considering, we can help with your rpm at speed calculations.
Keep in mind that unless you've got your original drivetrain (sounds like you do) AND original tire diameter, your speedometer will be incorrect.
I can tell you from experience that, if you're NOT gonna do burnouts and you have a mild engine, that a T5 is a fun swap and very driveable - will give you plenty of options for your hills, good accel from a stop (without burnouts) and a great cruising rpm. If you want to stick with the original 3OTT, completely understand. I swapped my 66's 3 spd for a T5 and it was fun to drive.

[harpo231]

just cruisin 3:42

[bubbasimms]

Definitely.no burnouts, no hauling and no towing. And definitely keeping the 3 Ott and 250. Just cruising and looking sexy.

[Mike C]

The ultimate inline 6 truck would be created with the addition of a T5 from an S10 with the 4.3. Accelerate better, cruise better, be more fun, better fuel economy, etc.

If you are paying someone do R&R your diff with new gears my guess is $500 at the cheapest and probably closer to 7.

I know you may want to keep the 3 OTT shifter setup, but the T5 would make it a new truck.

[C10 - C90 Bill]

What is the 1st Gear in your 3-Speed? My '66 has a 2.94 which wasn't bad, but my '72 has a 2.85 1st. I can definitely tell the difference. I've got 3.73's and put on 265/75/15's on the back to help with the high speeds. It's a compromise, but it's about the best I can do with what I got. If you have a 2.85 and go with a 3.42 or 3.07 Rear, you won't be happy with starting off on a hill or driving slow speeds off road.

I just picked up a 4-Speed with a 3.11 1st. That will help with my low speed, but still will have that hi-way hassle, lol. After the 4-Speed a 3.42 would be nice.

[67ChevyRedneck]

I drove my 67 for years with a 250, 3 spd, and 3.73. I hated that combo, it was so loud above 55 and ran out of steam after 65/70.

It's now a 350/700R/3.73, a great combo.

I would recommend as suggested above, a NV3500 out of a 4.3L S10/S10 Blazer. You can keep the 3.73 and drop down into 4th to power up hills and pop it up into 5th and lower your RPM's 30%. Then you get the best of everything, power and fun when you need it, and quiet cruising with a littler better mpg.

[jocko]

Originally Posted by bubbasimms

Definitely.no burnouts, no hauling and no towing. And definitely keeping the 3 Ott and 250. Just cruising and looking sexy.

Then it sounds like a 3.4TWO is the gear for YOU!
Having said that, it's worth noting that a swap from 3.73 to 3.42 ONLY may not give you the dream-like cruising rpm you're hoping for. See the chart below, your rpms only drop by a couple hundred at 65 mph. T5 would drop them about a thousand rpm. Chart below for a 30" tire, but it's an apples to apples comparison. If you're set on the 3OTT, then the only decision is whether the cost of a rear gear swap is worth the resultant rpm drop. One note on the chart - some T5s have a 4.03 1st gear.

[bubbasimms]

Good info...thank you all.
It looks like I most likely have a 2.85 first gear in the old Saginaw 3 spd. I'm definitely not swapping trans. I know its a compromise in drivability to keep the 3 spd, but it's what I want. Most kids these days cannot drive a stick and many have never even seen one, let alone a column shifted manual and I want my young drivers to experience it. I drove it in the stock form for years and it was so smooth and quiet, I loved it. Just a little wound up on the highway. I have no interest in a tranny swap, matter of fact I just finished rebuilding the 3 spd last week. If needed I'll just float along low and slow.
I'm just looking for real world experience from anyone who may have changed the 3.73's out for something just a bit higher.

[bubbasimms]

MikeC....your about right on the money with the estimate from the couple places I have called.
Jocko....maybe the 3:42 and some TALL rubbers, lol.
Maybe I'll just leave it alone and stick to the right lane. Around here you can drop it in the Ozarks overdrive and fly down one side and slip it back into gear partway up the next hill. 90 down and 50 up make for a decent average.

[C10 - C90 Bill]

When I put the 265/75/15's on the back of my '72 C-10, it changed the 3.73's to about an equivalent of 3.63's. Not a big difference, but a noticeable difference at higher speeds. Plus I like the looks of them, lol. I have matching 235's on the Front.

[Mike C]

GM chose the 3.73 for the 6 cylinder as the base gear as it was the best for all around usage.

I think the best idea you have yet is to just slow down.

BUT, if you are willing to spend some money then a Gear Vendors overdrive can be used on the back of your 3 speed, but they are $$$$.

Another choice would be to look for a GM factory 3 speed with the electric overdrive on the back. They were fairly common in the late 50's and early 60's and aren't too complicated so can be serviced.

Then you can look into swapping to 4.10 gears and reap most of the rewards of a 5 speed conversion.

[KQQL IT]

Direct and 3.08's have always been my favorite

[C10 - C90 Bill]

Originally Posted by Mike C

Another choice would be to look for a GM factory 3 speed with the electric overdrive on the back. They were fairly common in the late 50's and early 60's and aren't too complicated so can be serviced.

I was considering going with one of those myself, but then you lose your synchronized 1st gear.

The newer ones with the synchronized 1st would be the way to go, but they seem to be pretty hard to find.

If I did locate one though, my Trans Rebuilder told me that he could swap the Overdrive to my Saginaw 4-Speed, giving me a pretty much factory type 5-Speed, covering both ends of having a nice low 1st and a nice cruising 5th.