Ford 9" rearend, how complicated??

[UATahoe]

My only real hesitation is the driveshaft piece of it. Not much experience there to really troubleshoot or fix. Coming out of an 84 i am assuming it was bolted up to an old th350 maybe? Not sure how that changes with the 700r4 or if a special driveshaft was needed even in the 84.

[UATahoe]

Just got some more info. The truck it was in also had the 700 tranny. The truck's one piece driveshaft fit perfectly so that is encouraging.

[LynnJr]

Ask him if it has the big "N' on the case.

[UATahoe]

Doesnt know what posi it is, but does know its not a detroit locker and its not a spool or mini spool.

[Rufton]

Originally Posted by LynnJr

Sorry about that.
Alot of people think there is something special about posi-traction and there isn't.It is simply limited slip and as time goes by it gets looser and looser.
Does the 9 inch have a detroit locker? A Detroit Locker works like Posi or Limited Slip.
In short none of the various names given to rear-ends means much.You either have.
One wheel spinning.
Sometimes two wheels spinning.
Both wheels locked and always spinning.
All the rest is marketing.

Yeah. Sometimes limited slip/posi is loose enough for one wheel burn outs

[LynnJr]

Yeah. Sometimes limited slip/posi is loose enough for one wheel burn outs





i have a 90 GMC that came with posi.
It lasted 57 miles before the drivers side axle fell out.
After they fixed the truck it lasted about a month before doing one legged burnouts.At less than 6 months it broke the carrier between the bearing and axle splines.$2200 later it lasted about one month and broke a second carrier.Took it to the rear-end shop and $1400 later it had a Auburn gear in it.Lasted about a month and was a one legger again.
Took it 4 wheeling and when the passenger side wheel lifted off the ground it clunked back and forth before breaking the Auburn gear.
Towed to the Rear-End shop were they put in a Eaton unit that lasted about one month before becoming a one legger.
Lasted about 9 months total before breaking.
Installed a factory one legger that lasted almost 4 years before whining so loud you couldn't hear the radio.
Put in a used posi from a wrecker that lasted about 1 month before it became a one legger.
Tried putting in a spool but everyone said it was no good you want a posi and that the chevy dealer and the Rear-End shop didn't set it up right or it would never have failed.
$2400 later I had it set-up the way it is supposed to be but they forgot to add any fluid.I almost made it home before it locked up ruining both rear tires and taking out a large section of fence.
When I got it back from the body shop it lasted about a month before exploding on my way to work.
I asked for a spool again and they put in a ARB Air Locker.Its been in there for quite a while without any other trouble.
I now recommend the 9 inch fords without any hesitation at all.My engine is rated at 215 hp and the biggest tires on the truck are 31x10.5x15.
I almost have my original purchase price into rear-ends and 4 wheel drive actuators.

[UATahoe]

So how much of a pain will It be to get the rear discs working properly? I know I will need a disc/disc master cylinder and a proportioning valve.
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[UATahoe]

Also, price is now 950. Asked if he would take 900 and he came back at 950.
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[Rufton]

Originally Posted by UATahoe

So how much of a pain will It be to get the rear discs working properly? I know I will need a disc/disc master cylinder and a proportioning valve.
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You don't need a disc master cylinder.
You may need a proportioning valve if rear locks up before front.
I would do a wet skid test (in safe area) w/o proportioning valve first.
Do you know piston surface area of front (disc?) and rear brake.

[UATahoe]

I don't. I believe the rear calipers are 4 piston and the fronts are just stock.
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[Rufton]

If you have 4 wheel disc brakes w/o proportioning valve the total piston surface area must be larger up front in most applications.

[UATahoe]

I actually don't mind running the valve. Seems like a no brainer. I also don't mind changing out the master cylinder if it would make things easier.
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[LynnJr]

Last time I had one of there catalogs they made an adjustable proportioning valve.You put it in place of your original valve and do a skid test.You then twist the knob and repeat until it is balanced.
Here is a link to there proportioning valves.They run from $45-$85 but I would call them before ordering.They are easy to deal with and will give you good advice.
http://www.wilwood.com/MasterCylinde...derValves.aspx

[UATahoe]

So how does the deal sound now at 950?
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[Rufton]

Originally Posted by UATahoe

I actually don't mind running the valve. Seems like a no brainer. I also don't mind changing out the master cylinder if it would make things easier.
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To make an educated guess for custom brakes you need to get the piston sizes in all calipers and in the master cylinder. Often master cylinder only has one bore size to service front and rear so it can be used in drum and disc applications.

[UATahoe]

Where is the valve located at that I should change to the adjustable proportioning valve?
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[LynnJr]

Its in the middle of the front cross member.Follow the two lines that come off the side of the master cylinder and they will go right to it just behind the radiator and under your fan.
The factory valve is not adjustable and has two small spacers about 1/4 inch thick that keep it off the frame a little.
On an aftermarket model you have to drill a second hole if the spacing is off.
I just walked out the front door and took 2 pictures of what yours will look like.

[UATahoe]

Awesome! So this is what i need? Also, notice it has an electrical plug in on the end of it. Does the factory valve have that?

Doesnt seem like it should be too hard to do. Especially right now while the motor is out. It seems like lately though most guys are having trouble with their rear disc conversions. Really dont want those headaches. I do know right now though, the rear drums seem to catch and sort of lock up really easily in any type of aggressive braking. I am guessing switching to discs would help that along with the prop valve.

[wraprail]

Originally Posted by LynnJr

Yeah. Sometimes limited slip/posi is loose enough for one wheel burn outs





i have a 90 GMC that came with posi.
It lasted 57 miles before the drivers side axle fell out.
After they fixed the truck it lasted about a month before doing one legged burnouts.At less than 6 months it broke the carrier between the bearing and axle splines.$2200 later it lasted about one month and broke a second carrier.Took it to the rear-end shop and $1400 later it had a Auburn gear in it.Lasted about a month and was a one legger again.
Took it 4 wheeling and when the passenger side wheel lifted off the ground it clunked back and forth before breaking the Auburn gear.
Towed to the Rear-End shop were they put in a Eaton unit that lasted about one month before becoming a one legger.
Lasted about 9 months total before breaking.
Installed a factory one legger that lasted almost 4 years before whining so loud you couldn't hear the radio.
Put in a used posi from a wrecker that lasted about 1 month before it became a one legger.
Tried putting in a spool but everyone said it was no good you want a posi and that the chevy dealer and the Rear-End shop didn't set it up right or it would never have failed.
$2400 later I had it set-up the way it is supposed to be but they forgot to add any fluid.I almost made it home before it locked up ruining both rear tires and taking out a large section of fence.
When I got it back from the body shop it lasted about a month before exploding on my way to work.
I asked for a spool again and they put in a ARB Air Locker.Its been in there for quite a while without any other trouble.
I now recommend the 9 inch fords without any hesitation at all.My engine is rated at 215 hp and the biggest tires on the truck are 31x10.5x15.
I almost have my original purchase price into rear-ends and 4 wheel drive actuators.

You blew up so many rear gears I lost count!
I think your problem is you are using the wrong LUBE.
When it comes to rear end lube some examples would be,
Gear Oil
Gear Lube
Hypoid Grease
90/w

I'm sure there are more,
But I have never heard anyone refer to rear end lube as FLUID!!!
Maybe you were using ATF? (automatic transmission FLUID)
What about brake fluid?
Power steering fluid?
But never have I heard anyone say "Check the Rear axle fluid"...
Never
So you must have been using brake fluid or some other FLUID in your 7 or so blown up rear axle assemblys and thats why the blew apart on you.
Just so you know from now on, you don't put FLUID in the axle assembly.

[Rufton]

Originally Posted by wraprail

But I have never heard anyone refer to rear end lube as FLUID!!!

Your right but the common term kinda sounds like something at doctors office.

[UATahoe]

Rufton, so the adjustable prop valve should be all i need right? Then i could dial in the right setting? If thats all i need then that is good news.

Right now, the rears lock up way too fast. I cant do any aggressive braking at all before the rear drums lock up and start to skid. Definitely doesnt feel right.

[Rufton]

Originally Posted by UATahoe

Rufton, so the adjustable prop valve should be all i need right? Then i could dial in the right setting? If thats all i need then that is good news.

Right now, the rears lock up way too fast. I cant do any aggressive braking at all before the rear drums lock up and start to skid. Definitely doesnt feel right.

Remove factory prop valve and install an adjustable prop valve. Make sure prop valve designed for your configuration; there is a limit to prop valve adjustment range. Should be fine unless your system grossly imbalanced. Takes less pressure to lock drum; that's why rear drum may lock when adding front disc to all drum system. If have all disc then need adjustable prop valve unless smaller caliper on rear.

[UATahoe]

Current setup is the factory disc/drum. Will be going to a disc/disc with the new rear.

Alos, the Ford rear came out of a longbed truck. I am guessing that shouldnt matter when it comes to bolting up to my short wheel base right? spring perches and shock locations should still be the same?

[Rufton]

Originally Posted by UATahoe

Current setup is the factory disc/drum. Will be going to a disc/disc with the new rear.

Alos, the Ford rear came out of a longbed truck. I am guessing that shouldnt matter when it comes to bolting up to my short wheel base right? spring perches and shock locations should still be the same?

Your rear locking up is probably due to a maintenance issue; faulty rear drums, etc.

Your truck came from factory w/ a highly biased prop valve. Most of the pressure is directed to the front. With functional OEM prop valve you could install a very large caliper in the rear w/o rear skid issue. I would first try w/o adjustable prop valve and do a safe skid test. Can easily add adjust prop valve if fails skid test.

[UATahoe]

I think the drum issue could be a faulty install. Just had all of the rear brakes reworked, pretty much new everything. Should have done it myslef. Oh well.

Why do some say you have to change out the master cylinder too? Seems to be a lot of conflicting info out there.