8 3/4 guru need your help
I'm certainly no guru, lol, but my neighbor, 69 Dart runs 9.50's at 140ish, leaves the line around 36-38 hundred off the trans brake. He runs an 8 3/4 489 shortened housing, axles and back brace on a 4 link and has had zero issues with it.
I have several cars with 8.75's, saying he runs 9.50 in a 69 dart is great, but is it running 9.50's in a factory weight 69 or is this like my friends 69 and it's 2800 lbs ?
Also he makes 300 runs a year or 6
Back brace does nothing for the cap issue to why they eventually break with the "iron case"
NO No No Dana, too heavy,too expensisve,Too hard to change gears........ but I agree they are strong.
I do rears all the time and i lift them with brakes on and deliver and or instal, the 60 and 9" with rotors and calipers are 18 lbs difference. I lift them all the time, there is no 50 90 100 lbs difference,
18 pounds
friend who I spoke to,broke a 8 3/4 few years ago
it hade moser axles
MW main and billet yoke
the pinion snap it was a 489
but the week before he drop a u joint
does the pinion hade something wrong who knows
and when the pinion snap in the same time one of the main broke
not the MW but the other one who was still an OE
I do think or hope should I say
if I built it right with
the MW main (x2)
billet yoke
billet adjuster
and maybe the back brace( I dont know why it help)
it could hold
the problem is I dont know if I could get the cash for a dana
new axle for it
and I dont know what else
think it will be much expensive with the dana
but with the dana I will do it ounce
I DONT KNOW WHAT TO DO!!!!!!!!!!!!!
If you don't see the street, toss the 89 case, buy the AL thru bolt case it then uses the 42 style R&P.
Then you won;t have a issue, if you do all street driving then you have a problem and will need the one for street and the other for the track.
I am over 500 passes on the AL cases with cars at factory weight leaving at 5800, in the mid 9's to low 10's.
Iron case and guess what, cap issues and maybe 60 passes, and that is WITH the MW billet caps.
I have thought about it and looked at it in the past and couldn't figure out how it could possibly crush the sleeve more. Figured you'd know. The only plus I see using a solid spacer (and this is just me) is it's easier for me to set the preload with shims rather than crush the sleeve down. The 2 I tried using a crush sleeve in I went a little too far and got them too tight so had to start over.
Actually it is much easier with the crush sleeve, thing is you probably don't do enough of them to see it, with the crush sleeve once you get within 8" lbs you make very very little increment turns, like 8 degrees, then rotate the pin a good few revolutions, recheck pre-load and if it's off a little lets say 4" lbs make a 3 degree pull.
It is very easy to go to much it's very little movement of the nut at that point.
The shims are more time consuming as you need to go totally apart and back together again and sometimes you need a .0015 difference to get it perfect and that turns into a sob problem.
The only thing i see with the shim over the sleeve is changing end yokes, it takes out all the care and makes it a stupid person replacement part. Knock the nut off and remove old , put on new, tighten nut back to 250/300 area and have a nice day, that doesn't happen with the sleeve.
The reason for the back brace is because as your car leaves the starting line, and your tires stay at the starting line because they are sticking, the housing will flex. When it does, the pinion trys to pull away from the ring gear.
This is why the ring gear begins to chip at the outter edge over time.The pinion is trying to break the ring gear teeth off.
A back brace is not going to save your rear end, but it will help.It is a must in HHP drag race applications.
A Ford 9" has a pinion support (2 bearings, 1 on each end),which helps keep the pinion inline with the ring gear.If you set a Ford 9" next to a 8 3/4 pumpkin, it will all make sense to you.Wimpier by design.
Also, look at a 8 3/4 axel housing, it is 2 pieces stamped together, then look at a 9" axel housing.
I sold my 8 3/4 ,430's, spool 31 spline axels, billet yoke complete for $1000.00 and it cost me a $1200.00 to build my killer narrowed 9" with Yukon nodular case, large Daytona aluminum bearing suport,Strange spool,billet 1320 yoke and 35 spline Moser axels all new......And I don't run a back brace with a transbrake, leaving @ 5500 RPM's all season.I even got 11" brakes as an upgrade out of the deal as a bonus!
Paint the 9" black, and no one will ever know the difference from a 8 3/4.
Quit while you are ahead and call Braden @ Quick Performance in Iowa:
http://www.quickperformance.com/
He also sells on Ebay, he is awesome.
There are some misinformation in here.
1. the back brace keeps the housing from flexing ONLY if the springs are able to by location on the tubes distance from the housing ends, or if you're running a 4 link or ladder bar.
Now the housing can flex simply from the tires LEVERAGE point from suspension location..
2. Now when the housing flexes what happens is each time you leave it holds that slight bend, you either notice something in time or you don't, then what happens are the AXLE pry the carrier out of the case.
3. The ring gear chipping is the MAIN cap movement issues the Iron 8.75 has and why they CHIP the gear, not the housing flexing.
Now lets pick apart the misconceptions of the 9"
1. You're using a AFTERMARKET case and have the sense to compare that to a Iron factory 8.75
Had you used a factory ford nodular case YOU would be that guy in the picture i provided above when it BREAKS the 3rd bearing housing, and when a 9" breaks, unlike a 8.75 you don't need a trans and shaft, but the 9" when it breaks it is 80% of the time because the 3rd bearing failed.
2. the 9" has 2 bearing just LIKE every diff pinion does, the 9" has them WAY to close together and WHY it NEEDS and MUST have the 3rd bearing BECAUSE it is always in a state of DEFLECTING from the RING gear underload, and WHY they NEED load bolts when you go faster.
Thats a lot of issues to deal with and they have a hp loss to deal with.
The 9" has stupid aftermarket support, it needs it or the factory stuff breaks, but they have the largest amount of gear choices and aftermarket support and simply because they are so so easy to work on and set up compared to any other diff.
You can set up the pin at one side of the bench and set the ring at the other side and join them make adjustments without total dissembling the diff.
That is the only positive point.
AS for the 9" housing not flexing, that is total bs, i have another customer who this one unlike the other 3 of which one had a simple back braced 9" on a ladder bar, this one had the braced housing also with a ladder bar and guess what happened, it flexed and flexed and making a burnout and rolling out it flexed again and pried the carrier right out.
Also the ford housings you buy you better pay CLOSE attention to, there are major differences and some are WAY lighter, those are for OVAL racing and even with the bracing they flex in drag cars at normal weights, like i have just explained.
The housings all flex depending ON the suspension attachment points on the housing, and this is why i always make all attachment points as close as possible to the bearing end to counteract the leverage trying to bend them, many other builders put the suspension attachments as inboard as they possibly can for all the room possible for the largest tires, but as i have been saying for years and years you don't all need 16" wide tires, you need to understand suspension set up, along with motor location and angles.
Dana's flex, 12 bolts flex, 8.8's flex, it all has to do with suspension mounting points in relation to the end.
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