experience swapping gears in rear diff?

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zixxer

Diamond Member
Jul 6, 2001
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Anyone done this? I need to go from ford 7.5 stock 3.45's to 4.10's, and am not really sure how complicated swapping only the gears is versus trying to find an entire new rear end


I don't care about positrac or anything like that. only the gearing.

EDIT:

I thought backlash didn't matter with an open diff?


Also, it's for a ford ranger. It has a 2.5l inline 4. I could not care any less at all about off roading/power/etc etc that you guys are flipping out about the 7.5 rear. It is not 4wd. It also does not snow here. I also don't care about baja-ing through anything.

I have 245/65-17 tires, and the stock 3.45 makes 5th gear useless. The rpm's run way way too low - let alone if I need to pull a small trailer. I want 3.73 or 4.10 to get the rpm's back to what they should be.
 
I Saw OJ

I Saw OJ

Diamond Member
Dec 13, 2004
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Originally posted by: DivideBYZero
I can do it up to about 10mph, then it gets difficult.
Click to expand...

:confused:

I believe it can get a bit complicated if you dont know what you are doing. There are a couple things like the backlash that you have to get just right oh the whole thing would be a flop.

I would take it to a shop that does that kind of thing all the time, they would it right the first time, quicker and with less headache.
 
Iron Woode

Iron Woode

Elite Member
Super Moderator
Oct 10, 1999
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Originally posted by: zixxer
Anyone done this? I need to go from ford 7.5 stock 3.45's to 4.10's, and am not really sure how complicated swapping only the gears is versus trying to find an entire new rear end


I don't care about positrac or anything like that. only the gearing.
Click to expand...
why are you using such a crappy rear axle? Do they even make new gears for something that crappy?

What vehicle is it?

You would be better off getting a stronger rear axle rather than swapping gears. It takes hours to swap out gears. You need special tools and the knowledge of how to use them properly. Getting a shop to do it will cost you hundreds of dollars.


 
iamwiz82

iamwiz82

Lifer
Jan 10, 2001
30,772
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Originally posted by: Demon-Xanth
In theory, it's really easy. In practice, there's alot of details you need to get right.
Click to expand...

Correct. It's a PITA and something I would rather pay someone else to do. Measurements have to be perfect. Otherwise in about 6 months you will be driving along and all of a sudden your diff will lock up and you will be in for a world of fun.

EDIT: And why bother with a 7.5?

EDIT2: I was on a trail ride with a guy who had his gears done by a friend and we were heading home at about 50MPH and his front diff. locked up due to improper backlash. Lots of smoke and odors followed.

EDIT3: Iron Woode beat me to it. It may be easier to find an easy diff to swap in with the gears you want, depending on the vehicle. I'd rather do that than deal with gearing :eek:
 
Demon-Xanth

Demon-Xanth

Lifer
Feb 15, 2000
20,551
2
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Originally posted by: Iron Woode
why are you using such a crappy rear axle? Do they even make new gears for something that crappy?
Click to expand...

Took me about 10 seconds of searching to find 3.45, 3.73, 4.10, 4.56 and 5.13 gears (about $200 a set). I could probably find more ratios by looking at the other pages that came up. :)

Edit:
looked at summit.
 
Iron Woode

Iron Woode

Elite Member
Super Moderator
Oct 10, 1999
31,307
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Originally posted by: Demon-Xanth
Originally posted by: Iron Woode
why are you using such a crappy rear axle? Do they even make new gears for something that crappy?
Click to expand...

Took me about 10 seconds of searching to find 3.45, 3.73, 4.10, 4.56 and 5.13 gears (about $200 a set). I could probably find more ratios by looking at the other pages that came up. :)

Edit:
looked at summit.
Click to expand...
still, why use a weak 7 1/2 axle? That's like me using my 7 1/4 and putting in 3.55 gears. It will break because it can't handle a high output engine. Wasting money on a weak axle is just stupid. He should find a better axle.

He still hasn't told us what car it is.
 
S

SuperSix

Elite Member
Oct 9, 1999
9,872
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Currie 9" FTW..

4.10 is STEEP, hope you either have a good overdrive or don't plan on driving ling distances at highway speeds.

 
Demon-Xanth

Demon-Xanth

Lifer
Feb 15, 2000
20,551
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If you do go out looking for an axle swap, I'm not sure if Ford does this or not, but it might worth keeping an eye out for to help on the search. (9.25" rear end, 3.55 trak-lock in that picture)
 
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GalvanizedYankee

Diamond Member
Oct 27, 2003
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Have a shop that sets up 3rd members do it for you. Generally what happens when the uninitiated try thier hand at it, is they end up with a howling rear-end :D It could be louder than the radio or A/C fan on high. Used gearing is difficult to set up in a different housing, but it can be done. New or used, gear sets MUST be matched. They are numbered for this purpose.

The best you can do is to clean the differential bowl well then bond a couple of strong magnets out of the splash stream that will grab onto metal swarf.


...Galvanized
 
G

grillmasterP

Senior member
Apr 2, 2000
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Originally posted by: zixxer
Anyone done this? I need to go from ford 7.5 stock 3.45's to 4.10's, and am not really sure how complicated swapping only the gears is versus trying to find an entire new rear end
I thought backlash didn't matter with an open diff?
Also, it's for a ford ranger. It has a 2.5l inline 4. I could not care any less at all about off roading/power/etc etc that you guys are flipping out about the 7.5 rear. It is not 4wd.
Click to expand...


If you have to ask.....its not a job that you can take on. Most mechanics are not comfortable with gear work for that matter. It helps to have the proper tools to measure preload & backlash..

I just finished regearing my ARB locked Tacoma from 4.10's to 4.30's.....
and recently helped a friend do a gear swap from 3.91 to 4.30 on a Tundra 4wd w/ lsd

In your case- the easiest/cost effective options will be to find a separate 4.10 third or to drop the third and bring in the third w/ new R&P gears to a reputable shop (to save $$$)



 
Z

zixxer

Diamond Member
Jul 6, 2001
7,326
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Originally posted by: grillmasterP
Originally posted by: zixxer
Anyone done this? I need to go from ford 7.5 stock 3.45's to 4.10's, and am not really sure how complicated swapping only the gears is versus trying to find an entire new rear end
I thought backlash didn't matter with an open diff?
Also, it's for a ford ranger. It has a 2.5l inline 4. I could not care any less at all about off roading/power/etc etc that you guys are flipping out about the 7.5 rear. It is not 4wd.
Click to expand...


If you have to ask.....its not a job that you can take on. Most mechanics are not comfortable with gear work for that matter. It helps to have the proper tools to measure preload & backlash..

I just finished regearing my ARB locked Tacoma from 4.10's to 4.30's.....
and recently helped a friend do a gear swap from 3.91 to 4.30 on a Tundra 4wd w/ lsd

In your case- the easiest/cost effective options will be to find a separate 4.10 third or to drop the third and bring in the third w/ new R&P gears to a reputable shop (to save $$$)
Click to expand...


Still noone has answered my question about backlash - I was under the impression that a rear end WITHOUT traction control does not need the backlash set -
 
E

essasin

Platinum Member
Mar 4, 2004
2,777
0
0
You need to be experienced to install gears. Also remember that when you change your gear you have to buy other supporting parts and most importantly recalibrate your speedo.
 
Demon-Xanth

Demon-Xanth

Lifer
Feb 15, 2000
20,551
2
81
Not always, my speed is read off the ring gear. Changing the tire size is the only thing that affects the speedometer.
 
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