[font size=1" color="#FF0000]LAST EDITED ON Feb-04-01 AT 11:20 PM (CST)[/font][p]HI! A short time ago I asked how I could change the ratio of my rearend on my 1965 C-20. I thought it had a ratio of 3.90, but as it turns out it is a 4.57:1. So do any of you now what I can do to change the gears, or do I have to get a diffrent rearend from a diffrent truck? Thnks a bunck, Mikef
Hi Mikef, I was HIGHLY suspicious of you having a 3.90 rear end when you said your top speed was 60. 4.57 sounds about right. You're pulling HIGH rpms at 60. Depending on your actual wheel diamater, you could be turning as many as 3500 rpm. That's murder on your engine (not to mention your fuel economy). But with that gearset you could nearly pull a house! There are several possible solutions to get accomplish what you're looking for. But first you should think about the end result (what you want) before you do anything. You're obviously looking for lower rpms and a higher cruising speed. Are you wanting to retain your present towing and hauling capabilities? If so, then you should NOT consider going with a much higher geared rear end. Your best option would be to change over to an automatic and install a 700R4 overdrive transmission. Even with your present rear end you'd have a final drive ratio very close to that of the 3.08 (3.20 to be exact) and you still wouldn't lose any pulling power. However this is the most expensive solution as the conversion won't come cheap. There will be quite a few modifications to make (drive shaft shortening, adding transmission cooler, etc.). And a good 700R4 is expensive. But if your truck will mainly be a daily driver or cruiser, and pulling and towing are the least of your worries, then go for the 3.08. That's what I plan on doing with my '66 stepside. It'll put you at approx. 2350 rpm at 60 mph. You could also CRUISE on the interstates with the rest of the traffic at about 2850 rpm at 75 mph. That is a very pretty picture. You can search salvage yard for the lower geared rear end. From what I understand, finding a 3.08 12-bolt rear end is a very tedious task. I was very fortunate to find one for sale at traderonline.com for 125 bucks! Axle to axle. And it's 6 lug drum brake at that. These are VERY rare. Since the brakes, wheel cylinders, seals and brake lines are shot, I'm just going to use the "chunk" (not the whole axle). A local shop is going to change the third member for me for 125 bucks. This'll give me a high speed changeover for a complete cost of 250 bucks. I think the optimum setup is that which many new GM fullsize pickups are running today. That is the 3.73 posi rear end with the 700R4 transmission. Let's you pull strong and cruise on the interstates. Finding a 6 lug 3.73 posi is not very difficult as there were many produced. If nothing else, I'd at least change to a 3.73 if I were you. Even without the overdrive tranny. The availability of the rear ends is pretty good and the conversion costs would be fairly inexpensive. You'd also turn about 2800 rpm at 60 (not too bad). And you still would have very good pulling capability. Hope I've helped.
[font size=1" color="#FF0000]LAST EDITED ON Feb-05-01 AT 12:44 PM (CST)[/font][p]HI! Thanks for the help. I think I will look for the 3.73 rearend, I surthat is exactly what I'am looking for. I'am only 19 years old and this is the first vehicle I've ever restored. I have very little knoledge and experience dealing with cars and trucks and I appricate your help in restoring my first classic truck. Thanks again. Mikef
MIKE MY 65 HAD 3.73 AND I CHANGED IT OVER TO 3.08's,I GOT MY GEARS OUT OF A 77 PICKUP THAT I STRIPED FOR IT'S DISK BRAKES ALL THE GM 12 BOLTS FOR PICKUP's USE THE SAME GEARS SO IF YOU CAN FIND A TRUCK WITH A STICK TRAN.'s IT SHOULD HAVE YOUR GEARS USE THE CARRIER WITH THE GEARS YOU FIND AND YOU SHOULD NOT HAVE TO MAKE ALOT OF ADJUSTMENTS(BUY YOUR SELF A REPAIR MANUEL AND USE IT) HAYWAGON
