9" diff... What to do? - Ford Forums - Mustang Forum, Ford Trucks, Ford Focus and Ford Cars

xdc351 · 07-14-2003, 02:29

I have a 9" LSD with a 3.5:1 center, 28 spline axles and disk brakes in my XD falcon.

I am considering selling it and looking for a 31-35 spline unit and slapping in a full spool and a set of 3.7 / 3.9 gears.

Has anyone tried this sort of a setup before? How much did it cost? How easy was a 31 spline diff to locate?

Any tips would be great!

Thanks everyone.

XDC-351

WBT56 · 07-14-2003, 03:57

A) Keep the housing and brakes, just get new axles and get the centre rebuilt.
B) What is the application? Why do you need 31 spline?

Soxx · 07-14-2003, 06:53

Are you having problems with the 28 spline? If not don't bother changing, just have your clutches packe tighter.
In any case, the 31 spline isn't much stronger than 28 spline, but 35 splines axles are much stronger than both.

Rick.

xdc351 · 07-14-2003, 18:32

First off let me correct my last post. I know 28 and 31 spline diffs use the same housing, i just don't know how to communicate this after a couple of beers! My question was ment to be has anyone tried to locate a 35 spline diff and how easy was it.

I have had some minor problems in the past with warped axles, having bigger problems with the seals/bearings taking the abuse of hard launches, and its only been on the street/easternats and i'm not doing burnouts. I'm worried that as soon as I start taking it to the drags i'm gonna stuff another axle/bearing/seal, etc. I've had the diff rebuilt and the clutch pack is as tight as it will go.

Looking to maybe replace the bearing + seals and sell this 9" and get a 35 spline unit and stuff a full spool in it.

I have never owned a 35 spline 9" before so i'm wondering how much better they take hard launches/decent burnouts? Do the larger bearings survive longer? Are the seals any different/better?

Any advise would be appreciated.

WBT56 · 07-15-2003, 03:40

Do you get much axle tramp? This will kill wheel bearings. A properly set up 28 spline should hold 500fwhp. I know a bloke with a 580 fwhp (engine dyno) 378C that I rebuilt the 4.11 28 spline LSD for. Layed two big black ones up the road to "test it was good enough" as he left. Hasn't played up.

Racer · 07-15-2003, 04:00

You shouldn't have problems with 28 spline with 270rwhp. 35 spline is overkill and will cost you a small fortune because everything but the housing will need to be thrown away. 35 spline only come in detroit locker (fairly rare) and full spool types, so it isn't really suitable for street use anyway.

Traction, heavy cars, and a lot of HP is usually what breaks 9 inches. In other words, slicks on a race track. Even then, it's usually only manuals that have troubles. I have a mate with hundreds of 9 second passes on 28 spline and 800hp (its an auto, and now 31 spline)

I've been through a heap of broken centres. I've twisted axles (31 spline) but never broken any. That is with launching at 6,500rpm with a toploader and a fair dose of HP.

Racer · 07-15-2003, 04:00

You shouldn't have problems with 28 spline with 270rwhp. 35 spline is overkill and will cost you a small fortune because everything but the housing will need to be thrown away. 35 spline only come in detroit locker (fairly rare) and full spool types, so it isn't really suitable for street use anyway.

Traction, heavy cars, and a lot of HP is usually what breaks 9 inches. In other words, slicks on a race track. Even then, it's usually only manuals that have troubles. I have a mate with hundreds of 9 second passes on 28 spline and 800hp (its an auto, and now 31 spline)

I've been through a heap of broken centres. I've twisted axles (31 spline) but never broken any. That is with launching at 6,500rpm with a toploader and a fair dose of HP.

brenx · 07-15-2003, 05:13

I have to agree with everyone else here. Your power doesn't warrant 35 spline.

I've smashed a bellhousing and twisted the input shaft on a c4. Guess what! 28 spline axles are still perfectly straight.

If your having bearing issues? I'd suggest looking at the actual axles. As disc 9" rears chew out the axles. I had to sort through quite a few axles to find ones that the bearings hadn't chewed out.

If the axles are totally stuffed. They'll also chew out your seals. They are about $150-180ea reco c/o.

I've been there done that with the XC disc rearend I have in my XB.

[edit] I am looking at breaking the 500hp+ range very soon. As I am tossing my big port 2V heads and going alloys.

Brenden

xdc351 · 07-15-2003, 16:43

Thanks for the replys all.

I'll be sticking with the 28's for now but I'm going to try canning the disks and putting some XYGT finned drums on there to reduce the load on my bearings + seals. It will be a shame to see the disks go tho, the car stops as well as my mates XR8.

WBT56 · 07-16-2003, 03:35

Housing, axles and bearings are (generally) different between drum and disc brake.