What transmission can I put in my 1969 chevy 4x4 pickup with a 350 small block that will help improve gas mileage and bring the rpm down. It currently has a 4-speed manual with low gear. What other things can I do to improve gas mileage on my truck?
What is your rear axle ratio? Changing that might help a little. But there’s not a lot you can do.
You would be better off changing your axle ratios (front and rear) instead of the transmission.
Put a 700R in it. Very easy to do. You have 3.73 or 4.10 gear in that. Most likely a 3.73. The tag on axle will tell what it is. Leave the gear alone and put a 700R in it ,you will be impressed. Google the swap for what you will need. I have friends that have done it. Its all a bolt in swap.
Trade it in for a 4 cyl. The change in axle ratios will help, but in normal driving other then the highway, you will notice little difference in this comparative gas hog. Just being very conservative and diving it slowly will make the most difference. I don’t know if I would drive a 69 4wd much over 60 mph anyway.
If it’s a four speed with a low gear it is a work truck like a farmer would want to own. You should leave that transmission in it unless you’re never going to pull heavy loads uphill for short distances. You won’t improve fuel economy enough to notice, even with a smaller engine.
On the plus side, some people are willing to pay for your transmission because they own a boat and are stuck with a five speed in their current truck. Somebody with a six cylinder and three on the tree would love to have your transmission to get that boat out of the water, so don’t just give it away unless nobody offers to buy it. Auto nuts have stuff to trade, like transmissions.