1965 Gears too low! What to do?

[1965Cowboy]

65 chevy with a slightly built 327. original 3speed & rear
I'm tachin like 3500 at 55-60mph whats the best way to getsome top end? also did the 6 cyl trucks come with a lower rear than the 8 cyl?
I've got a 66 that came with a V8 would this be a better rear?

[faribran]

Manual syncronized 3 speed over-drive.

[lakeroadster]

Use this chart:

http://www.sierrabronco.com/TireGearRatio.htm

and the following:

Pulling the rear differential cover (& counting the teeth) is the most accurate method to determine gear ratio but another way to check the rear end ratio is to jack up one tire if you have an open diff, or both tires if you have a working posi or locking differential. Rotate the tire one full revolution for posis and lockers -or- 2 full revolutions for open diffs. Carefully count the number of full revolutions the driveshaft makes. This is your gear ratio. In other words, if the drive shaft turns 3 ¾ turns, you probably have a 3.73 gear ratio. Turning the tire for twice the number of full revolutions and dividing the drive shaft revolutions by two will give you a more accurate reading.

Now you also need to be sure your transmission has the correct first gear ratio: This helps to determine that: http://www.5speedtransmissions.com/startlineratio.html

[astrochimp]

You can swap your 3 sp to a 5 sp, change rear gears (or rear end) or both.

These are the links I have saved for a 5sp swap-

http://www.jalopyjournal.com/forum/s...d.php?t=169265

http://67-72chevytrucks.com/vboard/s...d.php?t=313954

http://hamiltonintakes.com/products/s10t-5-adapter.html

http://www.transmissioncenter.net/


David

[markeb01]

Switching to a taller rear tire will also change the effective gear ratio lowering engine speed with no other mechanical modifications. This may or may not be practical depending on the size of your existing tires. The taller tires will also require recalibrating your speedometer to insure an accurate reading.

[1965Cowboy]

Originally Posted by lakeroadster

Use this chart:

http://www.sierrabronco.com/TireGearRatio.htm

and the following:

Pulling the rear differential cover (& counting the teeth) is the most accurate method to determine gear ratio but another way to check the rear end ratio is to jack up one tire if you have an open diff, or both tires if you have a working posi or locking differential. Rotate the tire one full revolution for posis and lockers -or- 2 full revolutions for open diffs. Carefully count the number of full revolutions the driveshaft makes. This is your gear ratio. In other words, if the drive shaft turns 3 ¾ turns, you probably have a 3.73 gear ratio. Turning the tire for twice the number of full revolutions and dividing the drive shaft revolutions by two will give you a more accurate reading

Used your method and found out that my truck that came with a 6 stock has 4.11 and my truck that came with the v8 has 3.73

[jocko]

cowboy - that sounds right - I have the 3.73 and all else is stock with a 3-speed and I'm doing about 3200 rpm at 70 (high, but bearable).

Only BIG solutions would be 5 speed or change the rear gear ratio. I'll tell you - for my case, even the 3.73 is a bit annoying. But a 5-speed would significantly lower your crusing rpm. Most 5-speeds are apprx a 0.7 o/d (some are more, some are less) - so your 4.11 becomes a 2.88 in 5th. Or, more appropriately put - your 3500 rpm would be approx 2450. That's still a little on the high rpm side if that's only at 55 mph. 70 mph would be proportionately higher.

I guess I'm saying that in the interest of cost - I think swapping the rear gear is your best bang for the buck. But then again - after you do that, yoiu've still got a 3 speed....

In my case - I think I can live with 3.73s if I go to a 5 speed.

Your other concern if you go to a 5-speed is the deep first gear - combined with your 4.11 will be quite the neck snapper. If that's what you're looking for - then go for it, but I'm thinking that might be a pain in the butt personally.

So - bang for the buck - Tall Tires like markeb01 said - but you're gonna have to go pretty tall to make a noticeable impact with 4.11s.
Effectiveness/driveability - rear gear swap.
Best of all worlds (if you have a money tree) - I'd go 5 speed and rear gear swap. At least with that option, you don't have to buy tires!..... Good thing too, you'll be broke.

[raycow]

Originally Posted by 1965Cowboy

I'm tachin like 3500 at 55-60mph whats the best way to getsome top end? ?

You might want to check your speedo calibration with a GPS. With a 3.73 gear and stock size tires (say about 27") you should only be turning about 2800 at 60.

That aside, I agree that the cheapest fix would be a rear end swap. Any 65-69 rear (and some 70) would be a direct replacement. 71-72 will bolt up too, but are about 1-1/2" wider and will have 5 lugs instead of 6.

For more flexibility you could replace your 3 speed with a 3 speed + overdrive (this was a factory option from 55 on) or a 5 speed from an S-10.

Ray

[6863m]

I just tried to change my rear brakes and I thought I had a 62 rear end and even though someone had changed out the 4/11 for 3/73 it would be the same but the hardware does not match. What I have is a 12 bolt rear end with six lugs. I am trying to order the right hardware kit. What year rear end could we have.

[Captainfab]

It is likely a '63-early '70 rear end. The first year for the truck 12 bolt was 1963, which had pressed on backing plates. '64 was the first year for the bolt on backing plates. The 6 lug versions in the C10's were from '63-'70.

Originally Posted by 6863m

I just tried to change my rear brakes and I thought I had a 62 rear end and even though someone had changed out the 4/11 for 3/73 it would be the same but the hardware does not match. What I have is a 12 bolt rear end with six lugs. I am trying to order the right hardware kit. What year rear end could we have.

[erock805]

Originally Posted by 1965Cowboy

65 chevy with a slightly built 327. original 3speed & rear
I'm tachin like 3500 at 55-60mph whats the best way to getsome top end? also did the 6 cyl trucks come with a lower rear than the 8 cyl?
I've got a 66 that came with a V8 would this be a better rear?

Best way is to goto a 5 spd fer sure, then play with your tire size. If you swap the diff you will lose a ton of acceleration...which you are prolly use to.

Cheapest way is swap out the diff.

[1965Cowboy]

never heard of that one. What do they come in/ where to find it?

[az65]

i put a 3.40 rear end in my 327/3spd truck and am able to blast 85 no prob now. Before the swap I had the same issue as you and would almost get run over on the freeway for having to go so slow. I think my previous rear was a 4.11 but I didn't count the teeth or anything.

[slorio]

3 speed with overdrive? Here's one for sale in Ohio:

http://cleveland.craigslist.org/pts/1861138397.html

Not mine, by the way, I already have one! LOL.

Here is some literature for those interested:
http://www.speedprint.com/deves50/overdriveindex.php

Search engine is also your friend. We have discussed this quite a bit in the past.
Regards,
Steve
New Orleans

[slorio]

Here's a 3 speed with overdrive on Ebay if you want to see a picture of what it looks like. This one is in Illinois. One note on these. The overdrive solenoid and governor are difficult to find if you need a replacement. If you have to ship, make sure they are removed and packed separately so they don't break in shipping. They hang off the sides of the transmission. Ask me how I know? Thanks to UPS!

http://cgi.ebay.com/ebaymotors/Munci...Q5fAccessories
I hope this is helpful.
regards,
Steve