Level of difficulty changing 8 3/4 gearing

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KIII

KIII

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1973 Dart Sport, 340,727, 8 3/4(2070741). My issue is that its geared way to low. The previous owner said he was'nt sure whats in the rear,maybe 3.73? Question#1. How hard is it to change out the rear gears? 1 being an oil change and 10 being an engine swap. #2. How much? #3. Where to purchase? Thanx.
 
changing the oil and changing an engine are both pretty easy with basic tools. Changing the gear ratio will require some indicators for measuring side play, backlash, etc and most likely a hydraulic press. It is not real hard but does require some knowledge to get it right. I would see if there is a member close to you that can help you set up the gears in the 3rd member once you get it out. I have done a number of them especially when we were jeeping a lot but am in no stretch of the imagination an expert. If you set them wrong, they will not wear properly and will be noisy or worse.
 
KIII said:
1973 Dart Sport, 340,727, 8 3/4(2070741). My issue is that its geared way to low. The previous owner said he was'nt sure whats in the rear,maybe 3.73? Question#1. How hard is it to change out the rear gears? 1 being an oil change and 10 being an engine swap. #2. How much? #3. Where to purchase? Thanx.
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Are you running a sure grip? If not it would be easier to just buy a good used assembly and install it. That would require no setting up the gears and if you shop around would likely be cheaper than buying a ring gear and pinion. that is the big advantage of having a 8 3/4 rear end.
 
well you will need a good jack two jack stands a socket to get lug nuts off a 3inch.extension a 9 1/6 socket maybe a small pry bar and a drain pan O and sum oil dri or kitty litter...and a first timer id say 2 1/2 hrs.and on a 1 to 10 maybe a 4..$$just a ring gear 200.00 and another 200.00 to get it set up.But myself I think a 373 gear is not that low of a gear.but that's my thut......Artie
 
KIII said:
1973 Dart Sport, 340,727, 8 3/4(2070741). My issue is that its geared way to low. The previous owner said he was'nt sure whats in the rear,maybe 3.73? Question#1. How hard is it to change out the rear gears? 1 being an oil change and 10 being an engine swap. #2. How much? #3. Where to purchase? Thanx.
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What is your engine RPM at 60 MPH. Knowing that will give us a good idea of your gears. Mine is 3000 that's with running 3.91 gears and 15" rear tire. As the guys said there are some specialized tools you're going to need but the biggest concern is the lack of gear ratio choices and availablility for the 741 center. This might be a good time to upgrade to the 742 or 489 center and the gear choices are many.
 
In terms of difficulty, it's more of a 4ish. In terms of special tools, I'd call it more of an 8 because there's things like the dial indicator, and rotating torque wrench, and either the pinion depth tool or a set of checking bearings, plus the bearing pullers and press, that make it more complicated. If you've never changed the ring and pinion, I'd advise to pay to have it done, or buy a complete center section unless you plan to invest in some tools and have shop air. Swapping the chucks is easy enough.
 
You might try raising both rear wheels with the trans in neutral and spinning a tire 1 revolution and count how many times the drive shaft rotates then say it's 3 1/4 turns it 's 3.23s etc.

I believe it's easier to change the whole center section (pumpkin, hog head). You can usualy pick them up reasonabl and just install it in your assembly. Basically you carefully slide the axle shafts out (enough to remove the centersection) then put the new one in, replace the shafts carefully (so you dont tear the seals. You will have to set endplay on 1 side.

Personally I would have a machine shop set up just a gear change if that's the route you go( special tools & equipment,as mentioned dial indicator, press etc).. You could remove the center section and bring it to them then to install the gears then you re-install the center section.
 
Check these articles and see if it's something you want to tackle.
http://www.moparmusclemagazine.com/howto/mopp_0308_mopar_rear_end_gears_set_up/viewall.html

http://www.carcraft.com/techarticles/ccrp_1006_mopar_83_4_inch_rear_axle_assembly/viewall.html
Search for Mopar 8-3/4 gear setup for more info. If you do decide to do it try to find someone experienced to check your work before you throw it back in the housing. After you've done a couple you will be good to go but the first couple are a bit tough to see if you've got it right or wrong.
 
You need a dial indicator, micrometer, press, torque wrench, a inch pound torque meter and a face spanner wrench.

If you have all of that then you have the tools to attempt it, if not it would be in your best interest to have someone qualified do it


OR, the good point on drop out centers is you buy another with the ratio you want and just swap them. . . .
 
grimreaper said:
Check these articles and see if it's something you want to tackle.
http://www.moparmusclemagazine.com/howto/mopp_0308_mopar_rear_end_gears_set_up/viewall.html

http://www.carcraft.com/techarticles/ccrp_1006_mopar_83_4_inch_rear_axle_assembly/viewall.html
Search for Mopar 8-3/4 gear setup for more info. If you do decide to do it try to find someone experienced to check your work before you throw it back in the housing. After you've done a couple you will be good to go but the first couple are a bit tough to see if you've got it right or wrong.
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Good lookin' out on the how to articles
 
If you truly have an 8 3/4 (your car would have come with an 8 1/4), changing the 3rd member is fairly easy. Changing the gears in your 3rd member takes a lot more knowledge and expertise. As mentioned, it would be a lot easier and probably cheaper to just swap out the whole 3rd member with one that has the gears you want. Freeway gears should be easy to find. An added benefit to that is you'll have an extra 3rd member for performance use or emergency repair. If you don't need a sure grip, I would have a 2.76, 2.93/4, and probably a 3.23 with the small (7260 2 1/8") u-joint. You're about 1 1/2 hours north of me.
 
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