my 54 looks like it has orig. rear p.o. said it is a 4.10 it really screams after 50 mph. question is what should i replace it with , hoe hard to do, & best place to buy parts. use about 50% around town 50% on highway .thanks mike

 

I recently put a 94 explorer in my 55, there are also a few 9" that will bolt up without any problems with the 5on 5 1/2 the explorer is a 4 1/2". Look in the tech articles, there is a list of rear ends to use.
Jaye

 

what i was hopeing to do was change gears in differ. i really don't want to change entire rear. will try search. thanks for reply mike

 

Might want to delete one of the double posts you have going.

 

i just had my rear end redone and it had 392 in it the tech had a chart that said with a 27 inch tall tire going 65 rpms would be about 3100 with 410 it would be and 3450 rpms if that helps

 

Had a 4.11 in mine but had to switch over to a 3.00......The motor RPMs were just too high with the 4 in it. Around 3000 RPM with the 3.00 going about 70 MPH....

Patrick

 

In theory, if I have a 4.88 in my truck and my top speed is 70 but my 0-30 acceleration is slow, if i switch over to a 3.00, my 0-30 acceleration will get better but my top speed will be lower.. is that right?

 

No, that is backward. The lower gears (higher numbers) mean that your engine turns more RPM at any speed. The way to set it up is to pick the RPM you want your engine to run when you are cruising down the highway, and size your tires and rear end ratio to produce that.

You use the transmission to get low end response - low gear for off the line, second for a jump around town, third for passing and high for high speed runs.

Nothing is perfect, so you have to do a lot of compromising to get as good as you can.

 

It will be difficult and expensive to change the gear ratio in the rear end you have now.
First you would need to find a brand new gear set of the right ratio for a 50 year old rear axle, you NEVER want to try to use a used set of gears in a different rear end.
AFAIK no one currently makes new gear sets for this axle, so you'd need to find a NOS (new old stock, not nitrous oxide!) set, people that deal in NOS parts think they are made of gold rather than steel. Second, there likely never was a NOS set made in a ratio you'd want anyhow, Ford built these trucks as work vehicles to haul 1000# of load over 15 miles of dirt road from town and across farmer's fields, not for cruising the Interstates, in fact Interstates hadn't even been invented yet, so there was no one who would have wanted a high rear gear set. Gas was less than 20 cents a gallon and the farmer only went to town for supplies and church so there was no need to drive over 30 MPH.
Even if you found a gear set it would be expensive to have it put in, the rear axle would need to come out of the truck and setting up a rear takes time and skill which = $$$. You'd be money ahead to find a later model replacement rear axle with the right ratio, there are plenty out there that bolt right in.

 

Another thing to keep in mind is that the rest of the truck was also not designed for modern highway speeds -- brakes, suspension, etc. This is why so many people are Darksiders. I wouldn't want to try to make an evasive maneuver in a stock early-50's truck doing 65...

But back to your original question, if you stick with the stock tranny (no OD), and "normal" tires (~28" rolling diameter), a 3.25 - 3.50 ratio will still let you get off the line without toasting your clutch, but will drop the rev's dramatically in the 50-55 mph range. There are several members here who actually use their trucks as trucks (hauling stuff) with these ratios.

 

thanks for the input sorry about double post mike

 

Mikeiz -

The compromises folks are talking about are regarding pickup from the line (stump-pulling power) vesus cruise rpm. You sacrifice one for the other, unless you have an OD tranny. Then you truly can have it all.

My 56 has a 9-inch in it out of a 57-59 truck. It is a bolt-on conversion and fairly inexpensive ($100-150 hub-to-hub for a good one ). Gear ratios are nearly limitless. My truck came with a one-legged 3.0:1 rear ratio. I cruised the SoCal freeways at 70 mph all the time. Rpms were around 2700 with 27" tall tires. I switched that rear end out for a 3.50 posi. 70 mph is now around 3200, but off the line is awsome!!! (Those rice rockets don't stand a chance!)

My truck is a street rod that also hauls stuff that is daily driven, so it's a wierd compromise. But the engine is a warmed over 351C, so I don't have a shortage of horsepower. That gives me a lot of choices. I chose to scoot around town and get poorer mileage on the freeway. One of our members has a 302 with and AOD and runs a high-geared rear end (around 2.23?). He crusies at such a low rpm that the tranny won't shift into OD. So, the possibilities are limitless. Think about what kind of driving you want and work from there. I'm guessing that a 3.0-3.25 rear end would serve most folks really well for all around driveability.

 

My truck is a weird exception..
Its pretty much not stock at all
Engine is a 302.. automatic c4 transmission.. Dana 60 rear end..
Its an F-250 so its a long-bed with the wider stance..
Bolt patterns are 8 lug..
I believe the stock rear-end for my year was a Timken.. (1955)
My truck was used as a wrecker. thats why the back of the bed was chopped off.. Used to have a boom, and needed clearence to haul the vehicles..
If thats the case, it probably has a lower gear ration than the stock 4.88..
It would be harder for me to find a replacement rear end with the same lug pattern and width, I presume..

 

There have been several posts on this in the past. Albuq and Randy have excellent suggestions. A good overall gearing for street and highway are the 3.25 and 3.50 gearing. I'd suggest hitting the junkyards. Most rearends will have an aluminum tag on one of the mounting bolts. It will tell you what gearing the 3rd member is. Example 3.50 = 3.50 gears. I've got 3.73 in mine with a standard C4 tranny. It does excellent on the street, however on the freeway I need to limit myself to 60 mph or the engines tach is higher than I care to drive for a distance. I'm not sure what AX is talking about being expensive? You only need a gasket to replace the gears. A 3rd member shouldn't cost you more than $150 and they are easy to find (at least in CA?) Pull the axles, removed the ten nuts, and pop the gear out. Pretty easy actually.

 

I found that the 3.92:1 ratio in my '51 F1 was a tad low for the brief jaunts up the local freeway. I found a guy in a nearby town who works out of his home garage that does nothing but differentials & jeep stuff; you get the picture. He had an nos set of 3.54:1 gears on his shelf and installed & dialed in this set. This was last Fall. I have the truck running again now but have yet to roll it out on the freeway; but took it up a steep side street the other day and it did just fine on the hill climb. (we're talking stock flathead & three-speed running gear). Can't wait to finish this restoration and get it back on the road.