Converting open diff to LS?

Silverado · Dec 15, 2007

How would I go about converting the open 7.5"/3.73 rear diff in my truck to LS?

Would I have to swap in a new axle with the right diff, or is it a matter of changing parts?

Thanks!

samsonitesamsonite · Dec 15, 2007

easiest way? grab a 3.73 L/S from a junkyard and throw it in.

Hahnsb2 · Dec 15, 2007

You can throw an LS carrier in or swap a whole LS axle. What are your plans for this? Off-road use I wouldn't waste my time on an LS.

Silverado · Dec 15, 2007

Light off road, mostly for bad road conditions.

metalmacguyver · Dec 15, 2007

swapping the carrier is one option but you should have the gears set up again for the new carrier and that will get to be more expensive than buying a used axle in the junkyard. also in the junkyard, its likely that you will find an 8.8 which is stronger and has bigger brakes and will bolt right in.

CraigK · Dec 16, 2007

metalmacguyver

"but you should have the gears set up again for the new carrier and that will get to be more expensive than buying a used axle in the junkyard"

Could you please elaborate on this? I have front and rear L/S carriers being shipped to me right now. Thank you.

CraigK

4LO 4.O · Dec 16, 2007

I think he's saying that by buying gears you'll have to have them swapped in to your axles and that usaully runs in the nieghborhood of $300. an axle

CraigK · Dec 16, 2007

Is this not something a reasonably competent "home mechanic" can do??? My intention was to install the carriages myself, upgrading from open to L/S axles at a fairly low cost (~$150 including shipping for the F and R carriers) and replacing the axle seals etc. while I'm at it.

No local junkyards had Bronco II L/S 3.73 axles, and prices for just a rear L/S axle alone were listed online at ~$250+ without shipping.

What about this conversion would require a $300/axle shop mechanic? Thanks.

CraigK

4LO 4.O · Dec 16, 2007

CraigK said:
Is this not something a reasonably competent "home mechanic" can do??? My intention was to install the carriages myself, upgrading from open to L/S axles at a fairly low cost (~$150 including shipping for the F and R carriers) and replacing the axle seals etc. while I'm at it.

No local junkyards had Bronco II L/S 3.73 axles, and prices for just a rear L/S axle alone were listed online at ~$250+ without shipping.

What about this conversion would require a $300/axle shop mechanic? Thanks.

CraigK

I'm not trying to down your abilities, it's not as simple as just trowing the new gears in- they have to mesh or they will render themselves useless rather fast, then back to square one.
Have you ever installed gears before? Do you know how to check the back lash or mesh pattern?
On a toyota for example, you can get a complete third member and it's as simple as un bolting the member and sliding the axle shafts, but a 8.8 doesn't have that option. You'll have to completely remove all the gears and re set up the gears.

CraigK · Dec 16, 2007

"they have to mesh or they will render themselves useless rather fast, then back to square one." Doesn't sound good . . .

"Have you ever installed gears before? Do you know how to check the back lash or mesh pattern?"
I have never installed gears before. I do not know how to check backlash. (Is this what is done with the mag base and dial indicator? - If so, I have these.)

I had never done most of the maintenance I now do myself before trying the first time, but I do not want to get in way over my head. (I do not do transmission work for example.) My question is what specifically is it about changing gears and replacing the open carriage with the L/S that requires a shop? Is there a good reference source for doing this work? Thanks.

CraigK

4LO 4.O · Dec 16, 2007

The mag base and dial indicator are the tools to set the back lash, so you are a step ahead.
I too do nearly all my own work, with the exception of auto trannies and gears
I am in no way trying to discourage you, and hope that you can do it yourself and pocket the $ for future modds.
Here's a link to help you better understand what is involved.
http://www.differentials.com/install.html

Barxxx · Dec 16, 2007

Use the search option. Theres plenty of info on this site & elsewhere. Its not an easy job if you're a novice. Do you have a friend with experience, that can guide you through this? For example, you'll have to set pinion depth & ring gear back lash. Then check the gear pattern using marking compound. Because the 7.5 or 8.8 are non removeable type third members, you'll have to work under the vehicle which makes it a little harder. The hardest part, in my opinion, is shimming the carrier to obtain the right backlash. Good Luck.

metalmacguyver · Dec 16, 2007

http://www.pirate4x4.com/tech/billavista/Gear_Setup/

the best gear article that i know of.

MAKG · Dec 16, 2007

Gear setup can be done as a DIY, but only if you are absolutely anal about getting it all JUST right.

Only backlash has to be set if the gearset is being reused and only the carrier is swapped. That doesn't affect pinion depth.

Silverado · Dec 16, 2007

@ Metalmac... GREAT article. Thanks for the link.

It's times like these that I miss my father. He was a race car builder and hot rodder from the good old days.

Converting open diff to LS?

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