8" Open differential conversion to limited slip?

[TexasEd 188]

Can an open differential be converted to a limited slip differential in the same houseing?

Does the existing open axle need any modifications?

 

Just curious about what is involved since I'm sure I can get by with an 8" behind my 302 and C4.

 

If there is a site with a good writeup on how to do this that would help me understand it all.

 

Thanks

[PaleRider 12]

Good thread on options

 

http://www.1969stang.com/mustang/forum/showthread.php?t=10660

[BigDuke6 17]

I converted my 9 inch LSD to a Detroit Locker. If an 8 inch works the same as a 9 inch, you should be able to simply swap out the center section.

[TexasEd 188]

I thought it might be cheaper to upgrade the innards of my 8" housing and not have to mess with drive shaft or axles.

 

If you put a 9" in what all has to change?

 

Sorry for my basic level questions.

[rwcstang 201]

ford 8" are good units and can be built to perform like a 9" but building it would probably come out to the same price if you were building a 9" hence, ppl tend tend to ditch the 8" and go with the larger popular setup.

 

you can build it, not saying you can't. i've seen some ol dragster still having ford 8" and they runs 10's on the track.

 

Im sure some more experience gents can help you out more in this field. Im still debating on my set up aswell since my 392 stroker is putting out 450hp lol..

[TexasEd 188]

So if you switch out to a 9" what has to change?

- Do you use the same axles?

- Do you have to modify the drive shaft?

[jholmes217 65]

Here's two articles from the Ford Muscle site. One is on axles, and the other is on the 3rd member.

http://www.fordmuscle.com/archives/1999/12/lockright/

http://www.fordmuscle.com/archives/2003/03/project67/

[rwcstang 201]

So if you switch out to a 9" what has to change?

- Do you use the same axles?

- Do you have to modify the drive shaft?

 

no, you would have to ditch your whole 8" setup unless its the same spline as the 9" or you can buy a complete setup with axles, housing, differential for about 2k+ from currie.

 

There are other brands besides currie, I just can't think of any. lol

 

thats only the housing and axles if u decide to just find a used 9" differential:

 

http://www.currieenterprises.com/cestore/productsCR.aspx?id=2704&p=1049.9500

 

also if you stick with ur 8" there's an eBay Seller that claims his ford 8" can handle up to 550hp I spoke with him, and he is very knowledgable. I haven't spoke to anyone who has bought his rearend so I'm not sure if its true what he says. he has a ton of good feedback but of course imo that is not enough.

[StephenC 10]

If you are considering getting a 9" check out Winter-Racing. I just had a Fab9 built by Jim over there and its exactly like the TCP Fab9 just at a much cheaper cost.

[TexasEd 188]

no, you would have to ditch your whole 8" setup unless its the same spline as the 9" or you can buy a complete setup with axles, housing, differential for about 2k+ from currie.

 

That's what I thought, which is why my original question was what is involved with converting my existing 8" to Limited Slip.

 

- I assume I use the same drive shaft and axles.

- Do I have to modify the open axle?

- Can I put the new LSD third member in the existing case?

 

From glancing at the first article jholmes 217 posted it looks like you can.

 

It referenced this site:

http://www.differentials.com/

[PaleRider 12]

You dont have to change axles or yoke.

You can buy a center section with gears and limited slip already done. If you look at the thread I posted there is a guy that sells threm thru ebay where a number of us had good luck with

Or you can buy limited slip ang gears and have someone that can do it fort you locally

 

I'm running an 8" with myu 347 - its about 400 hp/400 tq and no problems. I've heard of people throwing at lot more at them

[BigDuke6 17]

I thought it might be cheaper to upgrade the innards of my 8" housing and not have to mess with drive shaft or axles.

 

If you put a 9" in what all has to change?

 

Sorry for my basic level questions.

 

It may well be cheaper to stay with your 8 inch. What I was saying was that I swapped out the differential in my 9", going from a limited slip to a locker. If I was able to do it for a 9", there is no reason why you cannot swap out the differential in your 8"

[TexasEd 188]

Thanks guys.

 

I realize that buying a rebuilt 8" or 9" may be close in price, but its the domino effect that I was worried about.

 

If I go to 9" that requires new axles because the spline count is different and a new yoke on the drive shaft, etc.

 

I haven't made up my mind yet on what I'll do but at least I know what the consequences are. If I get to the point that I'm putting in an AOD which requires modifying the drive shaft then I'll probably do a 9" swap at the same time.

[LoneWolf2U 136]

Simply replace your center section with one that has the gear ratio and posi unit you want.

Running an auto will help keep it togeather, Unless your holding at the line with a tranbrake and sticky tires.

Most rearends fail from the shock and load from high rpm launches.

Ford's 8in can take alot of abuse. Changing to a 9in takes not only the housing but mounting plates and ubolts then you may have to rework the driveshaft and ujoints.

[buening 63]

Simply replace your center section with one that has the gear ratio and posi unit you want.

Running an auto will help keep it togeather, Unless your holding at the line with a tranbrake and sticky tires.

Most rearends fail from the shock and load from high rpm launches.

Ford's 8in can take alot of abuse. Changing to a 9in takes not only the housing but mounting plates and ubolts then you may have to rework the driveshaft and ujoints.

 

 

+1 For having a 302 and C4, unless you are boosted you aren't putting out enough torque to damage your 8" rear. Now if you have plans of creating a torque monster, then you may find your weak links (which the 8" would become at some point). You can find a trac-lok for an 8" pretty reasonably if you are on a budget....for example: http://www.ebay.com/itm/FORD-8-TRAC-LOCK-FROM-A-1970-FAIRLANE-/130659990381?pt=Motors_Car_Truck_Parts_Accessories&hash=item1e6bf13b6d&vxp=mtr

[rwcstang 201]

I remember when everyone started debating about the c4's. Everyone thought they were light, weak etc.. until someone made stronger parts they started to get a reputation of being beast handlers, lol.

 

lately, I have started to notice the same thing with ford 8", it seems ppl are throwing a lot at them. So I'm sure later on more better quality parts will come out and I'm sure they will get a great rep like the c4.

 

again, its all up to preference to the owner. I have seen some pretty well built 9's get destroyed and cars ran 11-12's. but like stated above its the high rpm + shock + sticky tires which will cause the rear to blow.

[BigDuke6 17]

That's what I thought, which is why my original question was what is involved with converting my existing 8" to Limited Slip.

 

- I assume I use the same drive shaft and axles.

- Do I have to modify the open axle?

- Can I put the new LSD third member in the existing case?

 

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you would reuse the same axels as now. You will use your same driveshaft. If it has to be shortened, it is no problem.

 

you would swap out the differentials, that is about all.

 

here is an Eaton Limited slip for your 8 inch at summit costing $509

 

here is a Currie limited slip for an 8 inch at summit costing $409

 

then there is a Moser limited slip at summit for $499.

 

there are lots more.

[TexasEd 188]

Thanks, It is becoming much more clear now.

 

So if I buy a new differential I would also need a new ring and pinion if I want a different gear ratio; correct? I think I currently have 2.73 and was thinking of something in the 3.5 range but the ebay one could come with 3.0 for just the extra shipping.

 

So for about $600-700 in parts plus labor and grease I could upgrade it, right?

If I could get that used one on ebay for less than half of new I'd probably be way ahead and make it a no brainer, right?

 

I'm thinking about asking the transmission guy coming to my house tonight if he would build it for me (I haven't asked if that's something he does but he's a one man shop).

 

Thanks for the patience and information. I have a tight budget and I'm trying not to go overboard. Limited Slip is an upgrade I think would be worth it if I can get it all done on a budget with used parts.

 

Again, my engine is a stock 302 2V. In the next 12-18 months I'll probably replace the intake, carb and heads and put on headers as long as the compression is still good.

Edited March 8, 2012 by TexasEd

[BigDuke6 17]

Thanks, It is becoming much more clear now.

 

So if I buy a new differential I would also need a new ring and pinion if I want a different gear ratio; correct? I think I currently have 2.73 and was thinking of something in the 3.5 range but the ebay one could come with 3.0 for just the extra shipping.

 

So for about $600-700 in parts plus labor and grease I could upgrade it, right?

If I could get that used one on ebay for less than half of new I'd probably be way ahead and make it a no brainer, right?

 

I'm thinking about asking the transmission guy coming to my house tonight if he would build it for me (I haven't asked if that's something he does but he's a one man shop).

 

T

 

whoever does it for you needs to know how to properly set the backlash. A LSD with a 3.55 or 3.8 ring (what is available for a ford 8") would be a huge improvement over what you have now.

[PaleRider 12]

That why I wnet with center section on ebay - inthe long run about the same or maybe even less and the person I got if from had a lot of good feeback. Really did not know anyone locally that could do it and I was concerned about backlash setting as BigDuke mentioned. I would not go with anything Taller (higher number) 3.5 with a c4. Running 3.44s and getting about 3k RPM

[TexasEd 188]

Thanks,

 

I think you're right (Y'all convinced this hard headed guy).

 

If I bought a new/rebuilt center section I would just have to connect to the drive shaft and slide the axles in, right?

[buening 63]

My personal opinion, you can save considerable money by going with the standard OEM style traclok over the typical Eaton Truetrac or Detroit Lockers. The OEM version uses clutch packs which will wear over time, but you likely won't put enough miles on your car to wear out. If you didn't have a tight budget and wanted the extra features, a Truetrac would be the best bet to get ($500ish just for the diff though). The Currie one is essentially an OEM style but with a few mods to beef it up (4 spider vs 2 spider of OEM). A rebuild kit is $65 from Currie http://www.currieenterprises.com/cestore/productsRE.aspx?id=1419

 

So for about $250 including labor you could have a rebuilt OEM one vs $400 for new. Throw in $100 for an installation kit and $200 for gears, and assuming your axles are in good shape you can replace the wheel bearings and seals. You should be in under $700 depending on labor charges.

[buening 63]

Here is one that appears to be fresh, although isn't coming from a reputable 3rd member rebuilder: http://www.ebay.com/itm/FORD-8-Differential-3-25-Trac-Loc-Perfect-Condition-/270928248570?pt=Motors_Car_Truck_Parts_Accessories&hash=item3f1494fefa&vxp=mtr

 

You'll drop $800+ for a rebuilt one from a reputable person on ebay: http://www.ebay.com/itm/FORD-MUSTANG-OR-STREET-ROD-8-EIGHT-INCH-REAR-TRAC-LOC-POSI-550hp-9-/330695181205?pt=Motors_Car_Truck_Parts_Accessories&hash=item4cfef80395&vxp=mtr

 

http://www.ebay.com/itm/FORD-MUSTANG-8-EIGHT-INCH-REAR-GEAR-TRAC-LOC-POSI-FORD-9-WITH-VARIOUS-RATIOS-/150768149650?pt=Motors_Car_Truck_Parts_Accessories&hash=item231a7b6492&vxp=mtr

[PaleRider 12]

Thanks,

 

I think you're right (Y'all convinced this hard headed guy).

 

If I bought a new/rebuilt center section I would just have to connect to the drive shaft and slide the axles in, right?

Yes - don't forget to put new axle seals. When I did mine it was about a 2 hour job

[rwcstang 201]

TexasEd- keep us posted and tell how that 8 rear end goes! :D