Random 4x4 question

[N.E fjord-by-fjord 2fiddy]

I bought a new rear axle off ebay this past june. Haven't needed to use 4 wheel since. I did today, and my rear wheels drag a couple inches every 1 1/2 rotations or so. I spent a lot of time making sure that the ratios matched between my Dana50 front, and what I was buying... but I think it looks like something is off. I know there are plenty of experts on here, so I was wondering if I got the axle codes from both, if someone could solve this mystery for me, as evidence suggests I am apparently not capable.

I'm assuming, since the backs drag, that whatever back axle the people in Alabama sold me is a bit more sluggish... I thought I had 3.73 in front, so maybe 4.10 gears is what they gave me?

Also, I assume that replacing the rear gear set will be the easiest to do, and cheapest? (since I don't have the time or space... got to get someone to do it for me.)

I'll get those axle codes up as soon as I can...

Thanks!

 

[Clb]

If someone regeared them 'then codes are junk.
I can't decode nothing right now.
Search axle code ratio's....
Sounds like either a mis match or bad r-p. Carrier setup.
But here's and easy way to get roughly what your ratios are turn the input pinion shaft one revolution count /mark the wheel at the bottom or wherever'( if you have open differentials have someone hold one wheel on one side of the truck axle while you turn the Pinion and count the opposing side 's wheel revolutions )- count how many turns it turns (tire)do that for the front and the rear they should be within a quarter turn of each other of being accurate that'll tell you What the ratios in the pumpkins are .

 

[crash-harris]

X2 on that. I always prefer to mark a tooth on each the ring and pinion gears and count/divide to verify ratios before installs.

I'm assuming your tire sizes are the same from front to rear as well. Bruiser is running 35's up front and 37's out back with 4.09/4.10 gears. Due to the measured height of the tires it works out fine, but the moment it hits hard pack/asphalt I can feel things start to bind. I try to unlock the hubs before I get to a hard surface, but if I can't, I'll unlock them asap and back up 10-15' to unbind everything.

 

[dunk]

I'm assuming, since the backs drag, that whatever back axle the people in Alabama sold me is a bit more sluggish... I thought I had 3.73 in front, so maybe 4.10 gears is what they gave me?

AFAIK Ford only offered 3.55:1 and 4.10:1 in the D50+Sterling from '80-'97, unless you or a PO changed it.

 

[riotwarrior]

Easiest way to check gear set.

2 people....3 would be qiicker.

One driver amd one or two spotters.

Mark tyre sidewall at 6 oclock...with chalk. Makr drive shaft or pinion so you can see mark while looking under truck.

SLOWLY drive forward while conting drive shaft revolutions until tyre makes one full revolution.

Now if you had 3 folks front n rear could be done at same time


Lock both hubs

TCASE IN 2WD
TCASE IN 2 WD
TCASE IN 2 WD

Mark tyre 6 oclock
Makr pinion

Again drive foward slowly... counting recoltions of drifve shaft.

Likely 4.10 on front

No idea what rear is...

4.10 = hair over 4 driveshaft revolutions
3.73 = 3 3/4 driv shaft revolutions
3.55 = 3 1/2 driveshaft revolutions.

Tyre size does not affect static gearing as measured above.

JM7.3CW

 

[lotzagoodstuff]

Add another vote for physically counting the ring and pinion teeth and doing the math to figuring out you gear ratios.

Second favorite one is the "Mel Method", which involves putting a piece of string around the driveshaft, marking and rotating the tire exactly one revolution, then measuring the amount of string that has wrapped it's way around the driveshaft.

Good luck, it sucks to put parts in and find out they aren't/weren't as advertised, but I'm sure you can sort it out.

 

[Clb]

X2 on that. I always prefer to mark a tooth on each the ring and pinion gears and count/divide to verify ratios before installs.

The only accurate way^^^ to be sure besides reading the factory markings!
Do let us know what you come up with!

 

[N.E fjord-by-fjord 2fiddy]

Thanks for the info... I'm pretty sure the gears were stock from '94. I have the Dana 50's code, and it says 3.54...

I can have my local tranny guy do this job, but we're getting into snow season now, so I can't do it myself.

I'm completely inexperienced in this department. Would a simple ring/pinion gear swap in the rear differential to 3.55 do the trick? (assuming the Dana was never changed, and it's still 3.54...)

 

[hce]

If you do not have lockers. Jack up both tires on one side. Place transfer case in 4wd lock in front hubs. If you have automatic hubs rotate rear wheel till front locks in. Mark both wheels in same spot, say 6'o clock. Rotate wheels by hand and marks should stay together. If not the case then you will have to get more technical and mark the driveshafts to determine ratio.

 

[N.E fjord-by-fjord 2fiddy]

Well now. I have the Dana code that says 3.54, and just got a message from the seller of that axle confirming that it was 3.55......
So it looks like one of the differentials were altered, or there's some other issue... I'll have my local guy give it a look asap. Is there something else that could be creating the occasional back tire drag other than mismatched ratios? a t-case issue?

 

[DaveBen]

No they are the same. Some times they put a slightly different ratio in the front vs the rear to take up slack in the running gear. (Old trick). Get it.

Dave

 

[N.E fjord-by-fjord 2fiddy]

No they are the same. Some times they put a slightly different ratio in the front vs the rear to take up slack in the running gear. (Old trick). Get it.

Dave

Read the whole thread... One of the diffs may have been altered. That's what I need to diagnose. I know 3.54 and 3.55 are close enough...

 

[Waystro]

Did the D50s come with 3.54 gears tho? Seems rare
I might have missed it but what year is this rear axle from?

 

[chris142]

Did the D50s come with 3.54 gears tho? Seems rare
?

Seems more common than 4.10's

 

[79jasper]

Definitely more common. That's what my 88 had.

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