Gearing ratio ?

[kmac530]

I have been scouring the country for a set of 4.11:1 gears for my diff. NOPE. Zip, zero, ziltch, nada...N/A.

But, I did find a set of 4.86:1 gears for my rearend. I am tempted to buy them. I was not interested at first because it is not enough of a difference from my 5.57:1 gears.

Do you folks think that 0.71:1 lower ratio is enough to be worth all of the work involved in swapping gears?

Side note: I have done gear swaps before and I am comfortable with 9" and Chevy 10/12/14 bolts and Dana style diffs. I am sure that this diff is different being a split center Timken, but I am sure I can figure it out with my manual and all of your input if I get in trouble.

I started considering doing the swap after talking to a friend about his rock crawler rig. He has 4.56:1 gears with 33" tires. Stock he had 3.73:1 and was running his 33" tires and the 0.82:1 change was a HUGE difference.
I realize that going from high 3s to mid 4s is not the same as going from high 4s to mid 5s, but if it is going to make a decent difference and is worth the work I may pop on them. He did not give me a price yet, but he made me feel like it would not be too bad on price.

Input?????

[candbstudebakers]

I have a 455 TT truck rear end for sale .

[kmac530]

I appreciate the thought Bob, but I am not wanting to change my old style 2R10 Timken split center diff. That is the hard part. Sorry if I was not clear on that. I had a whole other thread a few weeks back on what I have and why I will not change it...6x7.25 bolt pattern...

I was looking for the optional set of 4.11:1 gears for this diff, but as I soon learned...holy grail stuff.

[DieselJim]

http://www.network54.com/Forum/23885/message/1161400724/

[candbstudebakers]

I appreciate the thought Bob, but I am not wanting to change my old style 2R10 Timken split center diff. That is the hard part. Sorry if I was not clear on that. I had a whole other thread a few weeks back on what I have and why I will not change it...6x7.25 bolt pattern...

I was looking for the optional set of 4.11:1 gears for this diff, but as I soon learned...holy grail stuff.

Ya I remember that now, good luck.

[kmac530]

http://www.network54.com/Forum/23885...ge/1161400724/

Again, NOT changing the diff itself...I LOVE the look of the split center, it is just too cool.
Just looking for opinions on wheter it would be worth the time and effort to swap the gear out for only 0.71:1 ratio improvement.

[Pat Dilling]

Assuming a 30 inch tall tire you would see about a 500 rpm drop at 65 mph. Maybe this calculator will help.

http://www.csgnetwork.com/multirpmcalc.html

[PackardV8]

First, I agree completely. The '49-55 Budd 6-lug wheels make the truck. You don't want to lose those. The '56-64 Ford plain vanilla 8-lug wheels Stude used are just "meh."

As they say on NPR, "Let's do the numbers." It's about percentage change, not raw number change. The swap from 5.57 to 4.86 is only a 12.7% drop in RPMs. That's a help, but not much for the work involved. Your friend's gearing change from 4.56 to 3.73 was an 18.2% difference, or 50% greater change than yours would be.

Is the transmission another non-negotiable change? Having owned both, the 3-speed overdrive, with it's 30% reduction in RPMs, is a much better daily driver than the 4-speed.

Bottom line - here are the best options:

1. Continue to search for a Timken 4.11. Rare, but they're out there.

2. Change to a 3-speed with overdrive.

3. Give up the Timken but keep your six lug rear drums. Buy a 4.11 Dana 60 from a '56-64 Studebaker truck and switch the Timken backing plates, brakes and drums onto it. This will widen the rear tread by about 3", but will fit under stock fenders if the tires aren't too wide. If you want to keep the stock tread width, have the Dana 60 narrowed. Simple, inexpensive by anything other than CASO standards and most 4WD shops do this every day. It will look the same outside and only if someone crawls under it will they see the later center section.

jack vines

[eirenetheou]

Those "4.86" (4.857) gears are exactly what i have been looking to find, without success. With the overdrive now installed in my '49 2R10, they would bring the final drive ratio to 3.42, which is good enough for me.

If you determine that you don't want these gears, i am surely interested in them.

God's Peace to you.

d

[00RACER]

You can get them from either richmond gear or randys ring and pinion

[kmac530]

Pat and Jack,
Thanks for the math input, that was what I was looking for. I knew it was a percentage deal, but I did not have the formula to figure it out. Been along time since I have used anything other than basic math and Pi for construction....I am a framer/hanger, not an engineer. The 12% and 18% made it clear for me. Jack, I do have a 3 speed OD trans in my truck and I have a flat bed so it doesn't take much to see the cool looking rear end like it would with a full fendered bed. Jack you say keep looking they are out there.....any ideas where to look? I have looked in FL, KS, IN, MI, CA....every truck guy I can find. Every guy I contact says "oh maybe old XXXX has some of those" here is his number....no luck.

eirenetheou, I found the 4.86:1 at Vern Edigers place. I will PM you his email. He is a truck guy and has tons of parts around and he is in Kansas I believe. I do not think I want them now, so if you can use them, I will email him that you are interested and that I do not need them.

00Racer,
I do not think you can get the gears I need from either of those places. I will check for sure, but this is not a Dana or GM corporate diff. This is a very odd Timken split center that has not been used on many vehicles, and none I have been able to find for well over 50 years...very obsolete. I have been looking for a used set since new ones are just not out there.

[kmac530]

00Racer,
I just got off of the phone with both Randy's gear and Richmond and both said NO WAY quite emphatically. This is a riveted on ring to the carrier. You have to heat and smash the rivets to hold the ring gear on to the carrier like they used to do on Iron Girders on high rises.