Ford 9" Questions

[Fastbird93]

Ok, looks like I may be looking at a new rear end soon. I would prefer a 9" rear because I've heard of too many people breaking a 12 bolt with a manual tranny.

First, WHO sells these things?!?!?? I can't seem to find them. Found a couple but no info.

Second, anyone know if you can retain your 3 Channel ABS??

Here's what I'm looking at:

9" Rear End
Detroit Locker or Auburn Pro Series Posi (on the fence)
31 spline axles (don't like the reduced thickness of the added splines on the 35)
Aluminum Center Section
3.70 or 4.11 Gears (on the fence, I've got an M29 car)
1350 Yoke

Thoughts?

[fastTa]

The nice thing about going to a 9" and if you plan on using 8620 steel gears, then your choices of ring and pinio ratios are virtually unlimited. Their are many selections between 3.70 and 4.11. For instance, 3.75, 3.82, 3.89, 3.90, 3.95, 4.10. Yes, you will lose your ABS with the 9".

A 35 spline axle is much, much stronger than the 31 spline. It is all about the distribution of power over the number of splines. More splines = less load applied to each spline given the same amount of power applied to the axle.

I would stay away from a locker and just go with a spool if you want all out straight line acceleration. If this car will be steet driven significantly you might want to reconsider using a spooled or locked rear end. I don't know if you have ever driven a spooled or locked rear end on the steet, but it is a little herky jerky.

On a 9", 31 spline is the limit for running a posi or open rear end. 33 and up, you must use a locker or spool.

Detroit does make what they call a "soft locker" but I don't have any personal experience with it.

[Fastbird93]

Hmmm....sadly, after some confirmation, I won't get a 9 inch. I can't retain my 3 channel ABS......so......12 bolt here I come.

[Injuneer]

I think the choice would depend on how far you plan to take your car in terms of power. I haven't heard of anyone breaking the 12-bolt with an M6 or anything else. My Strange held up to 762HP when the car was an M6 with a Street Twin. A friend of mine took his Strange to 800+HP as an M6, then to a shade under 1,000HP with a TH400/trans-brake setup. If you plan to go above those kind of power level, the 9-inch makes sense.

But if you aren't planning to reach those levels, you are giving up some power, adding extra weight and creating some geometry problems.

-the 9-inch loses 3% more power than a 12-bolt.
-9-inch weighs more than a 12-bolt.
-9-inch drops the pinion centerline .75" and offets it to one side, making driveshaft and pinion angle setup more difficult.
-requires modifications to some after market parts.... e.g. TA mount, LCA brackets, etc.
-Above mentioned limit on 31-spline posi units. The 12-bolt can be equipped with an Eaton posi and 33-spline axles.
-ABS issues (not a problem with 4-channel TCS/ABS).
-awkward TA mount setups make the "quick swap" not quite as "quick" as you might expect.

All that said, the 9-inch offers a wider variety of ratios, as mentioned above, a variety of center-section materials of construction and features. But other than the wider variety of ratios, you don't need the other features unless you are looking at well over 800HP.

And as FastTA mentioned as well, the 35-spline axles are stronger.... that's why they make them. I don't think I would compromise with a 31-spline carrier/axles.

[Fastbird93]

Injuneer, what you just said REALLY put my mind at ease. I'm currently running a Street Twin and had my reservations about how a 12 bolt would take it, but you mentioning yourself and I'm assuming Baxter having both run fine with it helps a lot.

I've priced out a loaded up 12 bolt with a HD posi and 33 spline axles for about $2300. I think that's the way I'm going to head.

I've got a couple of guys trying to convince me to make the swap to an 8.8", but I don't see it being adventageous over the 12 bolt.

[Injuneer]

Just a remote possibility here at this point, but my 33-spline HD Eaton, with ABS reluctor may be for sale before the next racing season begins.

[Fastbird93]

Just a remote possibility here at this point, but my 33-spline HD Eaton, with ABS reluctor may be for sale before the next racing season begins.

Whole rear or just the eaton/reluctor (which is I take it for a 3 channel??)??

[Injuneer]

Just the Eaton posi. Switching to a spool - maybe. The reluctor is machined into the carrier, and it for the 3rd channel of the ABS. It requires a non-stock sensor though.

[Fastbird93]

Have any more info on the "non-stock" sensor?? Would this be something that I could use as a standby or replacement?

Here's another question. ANyone know if Moser is/has changed their Torque arm mounting point to the stock style straight through design for the bolts?

[Injuneer]

The Strange 12-bolt requires the Strange ABS sensor. I doubt it would work with any other system. And it really doesn't work very well with the Strange system. That's one of the reasons I'm thinking of deleting the aBS system all together.

Last I heard, Moser was still using their poor design with the 4 individual bolts for the TA mount. It is a fairly constant topic of gripes on the CZ28.com "Drivetrain" forum. The holes are also offset toward one side, and require a TA mount with "Moser" hole locations in it.

[Fastbird93]

The Strange 12-bolt requires the Strange ABS sensor. I doubt it would work with any other system. And it really doesn't work very well with the Strange system. That's one of the reasons I'm thinking of deleting the aBS system all together.

Last I heard, Moser was still using their poor design with the 4 individual bolts for the TA mount. It is a fairly constant topic of gripes on the CZ28.com "Drivetrain" forum. The holes are also offset toward one side, and require a TA mount with "Moser" hole locations in it.

About the Moser TA holes, the reason I asked is because a guy over on the speed density board works at Spohn and he said that what he was getting from Steve is that moser has since changed the design.

I'm curious, how big of an impact is it to remove the ABS system?? I don't want to, but if Strange's setup doesn't work then I may consider it.

Actually right now the frontrunner for a new rear lies with Moser, but with the assembly/setup at some other shop. I'm also going to be calling Curry to see what they could do for me. So, we'll see.