Hi All,
I am looking at replacement parts to rebuild the rear end of my 54 F100 as I am hearing some noise coming from that area and there seems to be an over abundance of backlash,
I have never done this before so I am in the research mode right now.
As I see in the maintenance manual, the stock ratio is 3.92:1. I thought I wanted to change the rear to a little bit higher ratio because in first gear it seems a bit too low.
I swapped in a 5.0 and a T5 transmission so the rest of the gears seem to be just ok, it is just that first gear that I wanted to be a little bit better.
I think if I change the ratio, then I need to change the carrier (case) and unless there is another way, I will leave the ratio at the 3.92.

I haven't opened up the differential yet and am only looking at the maintenance manual, so I have some questions of you guys that have experience with this type of project.
1. What is the spline count on the stock axles?
2. Do the spider gears usually need to be replaced if the ring and pinion gears are replaced? (I doubt that the rear end has ever been worked on to replace anything.)
3. Is the stock rear end considered 8", 8.5", 8.8" or what?
4. Is the diameter of the ring gear the same as one of the above numbers? (In other words if the rear end is a 8" then, is that supposed to be the diameter of the ring gear?)
5. The parts breakdown in the manual shows one gasket with a flat top where the axle bearing and seal attaches to the axle tube. Mid Fifty has a pack of four gaskets. Two with the flat top and two with a notch at the top.
Does each axle require one gasket or two different gaskets?

I will probably have other question as I go along but this is all for now.

Thanks for any info or suggestions you can give nd I a sorry I couldn't make the below picture smaller.
Bob
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If you have the original rear end, it should be a Dana 44.

 

Yes I know that much. I just am not sure what is inside.

 

Ring gears are about 8.5" for the 3.92. The axles are 19 spline, which is different than many later, lower ratio D44 axles. The spider gears also are a different diameter where they seat into the carrier. If you change to a lower-number (taller R&P), you'll have to use spider gears made to match both, which are sold by Randy's, https://www.randysworldwide.com/shop/axles/?RTM=HP_TC_5_Axels_21.08.19&car[]=16280.
Going lower-number from 3.92 does require a carrier change.

Does your T5 have Mustang gearset or the S10 gears? The S10 1st gear is 4.10 ratio, will hardly get you across an intersection without shifting, but I would think a Mustang gearset would be pretty decent.

 

This transmission came out of a 91 Mustang. The first gear ratio is 3.35:1, second gear is 2.08:1, third gear is 1.38:1, fourth gear is 1.00:1 and fifth gear is .78:1.
The Mustang first gear 3.35:1 ratio doesn't look all that bad compared to the S10 first gear 4.10:1 ratio. I guess if I wanted some good quality aggravation, I could change out the first gear to something......? No maybe not!
Anyway, thanks for your input. All input is good information.

 

When I talked to my mechanic about making a gear change, because he suggested it. He said it is one job that is not a good idea for a guy with no experience to do. there is quite a bit involved i setting it up correctly. Then he told me a couple of stories of things gone bad.

 

Was he talking about changing the gear ratio or replacing the ring and pinion with the same ratio?

 

Why not just start in second gear?

 

Are you sure the backlash is an issue? I thought mine was too much, but I posted a video here and several folks say it’s normal.

As for first being too low, mine is too, 4 speed crashbox with a granny gear. I just use second. I think it would take a dramatic change in ratio to make first useful.

 

Setting one up for us was a time consuming process. I have set two up, both changing down to 3.54 from 3.92. Lots of assembly, checking pattern, then disassembly to add/subtract shims. The 44 we setup in our 52 build, I must have made at least 15 adjustments to get the pattern right, but the guys on here will help you. It does require a lot of tools, but I like new tools. You can make a set of setup bearings to help you. Do a lot of research and watch a few videos on it. Not only do you want a good pattern, you also want a non-leaker around the pinion seal and flange. Once you get the axle out and clean, it’s actually pretty rewarding work. Randy’s has a tech guy that is pretty good/responsive also.

JB

 

Thanks Brian,
I have a T5 so I like to use all five. I just thought changing the rear gear ratio might not be too hard to do. I probably will keep it as is though.

 

Thank Bob,
I also had the granny gear in the stock transmission and just used second gear, it was not fun. At this point I am doing my research and getting as much knowledge as
I can from the guys that have been through this process. You Tube is a pretty good resource.

 

Thanks for that information JB. When you went down to the 3.54 did you have to change the carrier? I do have most of the tools but will need some others. Some tools might be rentable. Did you use a spreader to get the carrier out?
Did you see a significant change as in the acceleration, highway speeds and shifting up and down through the gears? I might be able to find a coach around this area that would be willing to help me out also.

 

I have had multiple trucks with grannie low, so I would start in second. But if I had a load or trailer or starting on a hill I appreciated having the low first gear.

 

It was to change the gear ratio.