I have a 1980 Ford F-250 with a 4 speed. When I’m running like 65 the rpm is way to high and is screaming at me what gear ratio should I put in to where at higher speed it will have lower rpm but still have power when I want to mess around with it

 

Do you know what axle you have in there? I am running into the same problem, but on a Dana 60 the lowest you can get is 3.54 from what I have gathered. Since you have a manual truck. Overdrive might be something to look at.

 

The other option is to swap in a Dana 61 that will give you access to higher gearing.

 

If you don't mind converting to a hydraulic clutch, you can go with a zf 5 speed and have your cake and eat it too. You will have all the gearing you have now for pulling, and that 5th gear to drop the rpms down on the highway. If you can find a donor, you can have lots of little parts you may need, and be able to sell off the rest to get some of the cost back. You will need to be looking at somewhere around 1988-up f250 and f350's to get that transmission.

 

There are a few things to keep in mind with our trucks and axle gear ratio changes.
At the time out trucks were made the USA speed limit was 55 MPH and 65 MPH is not that much higher so should not be a big deal.
I also bet you drive something a lot more that has over drive transmission so the RPM would be lower and that is what you are use to and why the truck sounds like it is screaming.
You really need to install a tach to know just what that screaming RPM is.

Now for the axle ratio we also really need to know what you have to start with but just to use numbers lets say you have 3.55 gear.
Going to a 3.08, lower NUMBER not ratio, will lower the RPM but will also make it harder to take off from a stop and even harder with a load.
You will need to slip the clutch, wear it out faster, to get going. It will also feel like a dog, low on power from a stop.

Now going to a 4.10, higher NUMBER not ratio, will raise the RPM but will also make it easier to take off from a stop and even easier with a load.
You will not need to slip the clutch, less wear, to get going. It will also feel like you added a power adder, and really take off from a stop.

What you really need is an over drive added to your truck.
There were 2 different units you could add to your truck with the factory parts you have now, if they are good.
Gear Vender is one that bolts to the back of the transmission, stick or auto. If you have 4WD it cant be used in 4WD.

The other is Advance Adaptor's Range Splitter that bolts in front of a stick transmission so can be used in 4WD.
Here is the thing I seen posted that AA has stopped making the RS. Now I don't know if it was because of this virus or if there just not a call for it?
I ordered mine just as the virus hit and had to wait a long time for mine to be made and shipped.
From what I hear they make / machine all the parts In house and being you could not have a full staff is why mine took so long.
That may be and I hope for others, that just put it on hold till everything is back to normal but could call them to see.

The other option is installing a 5sp trans that has OD like a ZF5 or M5R2, do a search on ZF5 trans swap.
I could not find either local, wanted a ZF5 as I plan to pull a trailer, and with the ZF there were other parts needed besides the trans to make the install easier.
Also running the numbers for each option I found the AA RS was the way to go for me.
Dave ----

 

I've got an 86 F350, 4x4, 429 CJ (used to be a 460) T19 4 speed, Dana 60 front and !0 3/4 rear axle with 3.55 gears. At 65 MPH I am turning about 2500 RPM. I take off fine with no load but when pulling my camper or climbing hills it struggles. I am thinking of going to some 4.10 gears and a ZF5 trans in it.

 

Unusual you have problems at both ends. Usually you will have good low end power, but it screams at highway speeds. Or you don't have any pulling power, but it cruises at highway speeds. Do you have some sort of lopey cam in that 429?

 

If you have a 429 CJ and have issues taking off loaded or climbing hills then there is something seriously wrong. Your limiting factor on acceleration with that combination should be traction not gearing.

 

I didn't build the engine but it does have a mild cam. I'm changing it out this summer for a mid range cam that should help.

 

I didn't build the engine so not even sure it's a CJ.......yet. I did find that the distributor was not put in quite correctly, it was off a tooth for sure, maybe 2. I got it put in correctly and that helped a bunch. I'm also pretty sure the cam in it isn't right but it's getting changed this summer to one that Edelbrock recommended. They had also put a Quick Fuel 650cfm carb on that flooded the engine when the secondaries opened, a problem I couldn't seem to adjust out, so I removed it and put a Carter AVS 750cfm from a 69 Plymouith GTX on it. Another improvement. MPG's have improved too since my foot isn't in it as much.

 

Take the Carter AVS and find a deep lake and pitch it in, they are a contender for the worst 4bbl ever made. Well maybe not "the" worst but they are in the top 3 or 4
I would suggest one of summits M2008's carbs in it's place.

I would not mess with any gearing till you sort out the enigne fully. As you have NO idea what it is going to be like once the engine is running properly. So instead of dumping money into gearing put it into the engine where it sounds like it needs to go anyway...

 

I've ran Carter carbs for years, I know how to set them up, I'll keep it.

I fully intend to sort out my engine before dropping money on gears. That's what I have been doing all winter and I have seen progress. The previous owner had zero idea how to set up the engine I think. I need to get hooked up to the camper and pull it to see how it's helped that now.

 

If you have run carter carbs for years then you know the AVS is the single worst 4bbl carter built (and potentially the worst carb they built) all of them have fuel stability delivery issues. Not to mention if this is off a 383 the divorced choke will be missing.

There is a reason this carb was only offered for 2.5 years as an OEM part and was vehemently rejected on the aftermarket in the era becoming the butt of many jokes.. Dump the carter install a Summit or a Holley or even one of the new Edelbrock and the difference will be huge.