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rear replacing
#1
Not to get ahead of myself with my engine still on the stand, but I'm thinking of changing out the 2.75 single rear to stronger locking rear.. Is it less work to find a drum to drum unit and bolt in or pull the pumpkin and redo gears. Also wonder if it has to come from another mustang or others fit

Alan L

[Image: 1_30_09_13_10_12_32.png]
Alan L
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#2
Alan,

Since your car is a '72 Mach 1, I would think it came from the "Factory" with a 9 inch with 28 spline axles. The "stock" upgrade would be to 31 spline axles but I am not sure that is necessarily the way to go for your application.

Going to lower gears (higher numerically) does not necessarily mean you will have a "stronger" rear end; it simply means that everything being equal, you will usually accelerate quicker using a higher numerically gear set. This is fine for "quarter mile" racing but not necessarily fine for highway and day-to-day driving.

Many, many Fords, Lincoln and Mercury vehicles utilize the same 9 inch, 28 spline axles as your Mach 1, albeit many did not have the traction lok. We have had a couple "Fun Questions" on this subject. To answer one of your questions, it is far easier simply to interchange the "pumpkins" than the entire rear end.

Additionally, complete "pumpkins" (ring, pinion and traction lok/posi trac) are available from such companies as "Currie" and "Strange." Keep in mind that if you change you will need to match the "pumpkin" with the size of the axles.

Hope this helps.


BT

Do the RIGHT thing.
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#3
not2old;11114 Wrote:Not to get ahead of myself with my engine still on the stand, but I'm thinking of changing out the 2.75 single rear to stronger locking rear.. Is it less work to find a drum to drum unit and bolt in or pull the pumpkin and redo gears. Also wonder if it has to come from another mustang or others fit

Alan L

Alen,you can upgrade your center section,with a traction lock and differant gears.I have done that myself.You can re-use your 28spl axels with out issue.If you have a standard trans and or lot's of power and plan to run slicks etc...you should upgrade to the 31 spl axels,if not your 28s will work fine.
In either case I would just rebuild your current housing,assumming it is a 9in. housing.The only reason to swap out would be if you got a deal on a complete set up.My .02.


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#4
after doing something like this myself i can offer this perspective.

If your original Rear end is in good shape you can swap out your gears and diff for around 1000$

a new complete ready to install 3rd member will cost you about the same.

a complete ready to install will be ready to go, retro fitting your original will cost labor if you don't do it yourself.

going with the aftermarket allows you to buy a stronger product that is factory straight and should come with a guarantee.

if your 3rd member has damage to it the cost can shoot up past 1500$ very fast.

if your trying to keep the car original its one thing if you have room to store the original parts and don't care whats on the car. i would start looking into ready to install 3rd members with posi and the gear set you want already installed.

then all you have to do is drop out the old rear end, and pop on the new one and your ready to drive.

at that point your options really open up, you can build your axle any way you wish make it as strong as you want and can order it with a locker or posi in any gear set you wish 28 or 31 spline, of course you may want to beef up your axles 28 spline is fine.
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#5
72HCODE;11275 Wrote:after doing something like this myself i can offer this perspective.

If your original Rear end is in good shape you can swap out your gears and diff for around 1000$

a new complete ready to install 3rd member will cost you about the same.

a complete ready to install will be ready to go, retro fitting your original will cost labor if you don't do it yourself.

going with the aftermarket allows you to buy a stronger product that is factory straight and should come with a guarantee.

if your 3rd member has damage to it the cost can shoot up past 1500$ very fast.

if your trying to keep the car original its one thing if you have room to store the original parts and don't care whats on the car. i would start looking into ready to install 3rd members with posi and the gear set you want already installed.

then all you have to do is drop out the old rear end, and pop on the new one and your ready to drive.

at that point your options really open up, you can build your axle any way you wish make it as strong as you want and can order it with a locker or posi in any gear set you wish 28 or 31 spline, of course you may want to beef up your axles 28 spline is fine.
I agree on the ready to install third memebers.I am still trying to teach myself how to set mine up.I can do it but I still am trying to learn how to make a quite set up.I have two units that I am practicing on,a set of 3:50 and a set of 4:22s.
Like I said though I do not mind changing them out because I am learning.
For the price of one that is ready to go and all new it is hard to beat.By the time I have done mine a couple of times,with the cost of gears,bearings,seals,lube and my labor,new is defenatly cheaper.


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#6
^made sure you have a good complete set of shims from RATECH that will get the pinion depth setup

you want the coast side and the drive side mesh to look even and centered, in other words the mesh should occur level when you compare the coast side to the drive side. if one side looks higher then the other as you stare at it from the side, then change the shim slightly. it will never bee 100% perfect since they don't offer shims in .001 increments.

a good idea is take the pinion seal o-ring out when making adjustments, it makes it easy to pull the pinion nose on and off as you change shims.

on the deeper ratios you may find you can't pull the nose out once assembled because of the clearance between the ring and pinion gears, so what you can do strictly for setup is halve the spacer and slide them on from the sides, when you find exactly the spacer you need then pull everything apart and install a complete 1 piece spacer. then button it all up again.

after that setup the back lash according to what the gear manufacture states in the manual.

the trick is moving both backlash adjusters Equally on both sides of the chunk, place a mark on them so you know how much you moved them, its critical to keep the case spread in spec, one mistake people make is moving one cap less or more then another and have incorrect case spread ( preload on bearings).

remember to setup the preload on the pinion bearings as well and you should be good to go.

the biggest pain is having to rediscover the correct shim due to aftermarket pinion gears machining being different then ford oem.

one last thing. double check the runout of the back side of the ring gear with your dial indicator. make sure you are under .03" out of level, anything more then that and you will have problems and never get the backlash setup right.

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#7
72HCODE;11284 Wrote:^made sure you have a good complete set of shims from RATECH that will get the pinion depth setup

you want the coast side and the drive side mesh to look even and centered, in other words the mesh should occur level when you compare the coast side to the drive side. if one side looks higher then the other as you stare at it from the side, then change the shim slightly. it will never bee 100% perfect since they don't offer shims in .001 increments.

a good idea is take the pinion seal o-ring out when making adjustments, it makes it easy to pull the pinion nose on and off as you change shims.

on the deeper ratios you may find you can't pull the nose out once assembled because of the clearance between the ring and pinion gears, so what you can do strictly for setup is halve the spacer and slide them on from the sides, when you find exactly the spacer you need then pull everything apart and install a complete 1 piece spacer. then button it all up again.

after that setup the back lash according to what the gear manufacture states in the manual.

the trick is moving both backlash adjusters Equally on both sides of the chunk, place a mark on them so you know how much you moved them, its critical to keep the case spread in spec, one mistake people make is moving one cap less or more then another and have incorrect case spread ( preload on bearings).

remember to setup the preload on the pinion bearings as well and you should be good to go.

the biggest pain is having to rediscover the correct shim due to aftermarket pinion gears machining being different then ford oem.

one last thing. double check the runout of the back side of the ring gear with your dial indicator. make sure you are under .03" out of level, anything more then that and you will have problems and never get the backlash setup right.
I think I have found my issues.I have read so many different peaples post and watched so many videos that I completely missed the part about the case spread.I think that is where I am going wrong.
I have ckecked the run out,and have adjusted the side adjusters the smae each time.The problem has been I am not starting at the right place due to the lack of the case spread measurement.
I have looked like I got a good pattern every time but still get noise.the 3:50's I have in the car now sounds like a Pro stock car after a shut down and the engine off.When I am coasting it sounds like I have bad bearings,but they are all new.
As soon as I get the 4:22's back together I will swap them out,and go through the 3:50's and give them a going over.
Thanks for the in put 72HCODE

Sorry I hijacked your post Allen.It was not intentional.Good luck

[Image: 16kuyc0.jpg]
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#8
I think your posts were relevant FASTE.

I was hoping 72HCODE would post up on this thread - - glad that he did. I recall his well-documented "issues" in setting up the rear end in his car.

I think one of the core question Alan has to do with which way he should proceed with changing his rear end. Quite frankly, unless one is just dedicated to during the work his or herself, it is almost always more cost effective and less worrisome to do the "drop-in" thing, in my opinion.

BT

Do the RIGHT thing.
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#9
I've seen 9" pumkins around here rebuilt and set up to go for around 300-400. So the bigger question like Cobra brought up is how you want to go about it. Do it yourself or pay the piper, the choice is as easy as how deep are your pockets.
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#10
FastE;11289 Wrote:
72HCODE;11284 Wrote:^made sure you have a good complete set of shims from RATECH that will get the pinion depth setup

you want the coast side and the drive side mesh to look even and centered, in other words the mesh should occur level when you compare the coast side to the drive side. if one side looks higher then the other as you stare at it from the side, then change the shim slightly. it will never bee 100% perfect since they don't offer shims in .001 increments.

a good idea is take the pinion seal o-ring out when making adjustments, it makes it easy to pull the pinion nose on and off as you change shims.

on the deeper ratios you may find you can't pull the nose out once assembled because of the clearance between the ring and pinion gears, so what you can do strictly for setup is halve the spacer and slide them on from the sides, when you find exactly the spacer you need then pull everything apart and install a complete 1 piece spacer. then button it all up again.

after that setup the back lash according to what the gear manufacture states in the manual.

the trick is moving both backlash adjusters Equally on both sides of the chunk, place a mark on them so you know how much you moved them, its critical to keep the case spread in spec, one mistake people make is moving one cap less or more then another and have incorrect case spread ( preload on bearings).

remember to setup the preload on the pinion bearings as well and you should be good to go.

the biggest pain is having to rediscover the correct shim due to aftermarket pinion gears machining being different then ford oem.

one last thing. double check the runout of the back side of the ring gear with your dial indicator. make sure you are under .03" out of level, anything more then that and you will have problems and never get the backlash setup right.
I think I have found my issues.I have read so many different peaples post and watched so many videos that I completely missed the part about the case spread.I think that is where I am going wrong.
I have ckecked the run out,and have adjusted the side adjusters the smae each time.The problem has been I am not starting at the right place due to the lack of the case spread measurement.
I have looked like I got a good pattern every time but still get noise.the 3:50's I have in the car now sounds like a Pro stock car after a shut down and the engine off.When I am coasting it sounds like I have bad bearings,but they are all new.
As soon as I get the 4:22's back together I will swap them out,and go through the 3:50's and give them a going over.
Thanks for the in put 72HCODE

Sorry I hijacked your post Allen.It was not intentional.Good luck
My 3.50s whine loud the cars in front of me pull to the wright and wait for the fire truck to pass.lol
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