Questions on rear end gears.

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'70DartSwinger

'70DartSwinger

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I hoping to get some information on rear end gears,
I have a 1970 dodge dart swinger 340 4 speed car originally came with 391 gears.

The car now has 323, im looking to get some 391s, im just not sure what i need..

Ive looked in the for sale section and i see different posting for 391s
My questions are
what options do i have?
all i need is the gears right?
What is a clutch type?
Any info will help thanks!
 
What type of rear axle do you have? 8.25 or 8 3/4, I assume it won't be a 7.25 behind that 340 LOL. What you'll need depends on the axle you have.

You'll be able to just change the ring gear and pinion (need to be changes as a set) and keep the same carrier that you currently have. The ring and pinion will need to be setup properly and is most likely a job you should let a professional do unless you have the tools and the know how for it. Usually a transmission shop would be able to do this for you.

A clutch type refers to a sure-grip carrier. There are several types of axle carrier types, most common are the open-type (one wheel spinning) and the sure-grip type (both wheels spinning). The sure-grip unit can be found with either cones (the older type auburn) or with clutches. Clutches are the preferred type since they can be rebuilt easily.
 
the easiest way to do it would be to buy a complete pumpkin (center section) with the gears you want already installed and set up. Replacing the center section on an 8 3/4 can be done in your garage with simple tools and is pretty straight forward.

If you want to change the ring and pinion in your center section than you need to know what type of case you have (741, 742 or 489). The ring and pinions are different for each case, so you'll have to make sure you buy the correct one.
 
67cuda360 said:
the easiest way to do it would be to buy a complete pumpkin (center section) with the gears you want already installed and set up. Replacing the center section on an 8 3/4 can be done in your garage with simple tools and is pretty straight forward.

If you want to change the ring and pinion in your center section than you need to know what type of case you have (741, 742 or 489). The ring and pinions are different for each case, so you'll have to make sure you buy the correct one.
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I would just pay the extra $ and get complete pumpkin cause 3.91's are great gears on the street but going 120 km'h for long stretches can be $$ on fuel and comfort so you might want to use those 3.23's at times.

If your are going that route, you might want 4.10 gears since it won't see much steady high speed use
 
Thanks for the info guys yeah i think thats what i should do, is just buy the pumpkin
As for 4.10 i wont be doing that just stick with the 391s and yeah ill keep the 323s!
 
Yes, if that 489 pumpkin and 3.91 gears are in good condition (not worn) than it would be a direct bolt in in your 8.75. Maybe you'll have to switch over the u-joint on the drive shaft, depending on what case you currently have in the 8.75. At least I thought there might be some U-joint differences between the 8.75 center sections, maybe someone else can chime in on that.

The link you sent sounds like a great deal, but I assume it is the US correct, wonder what shipping would be LOL,
Good luck.
 
'70DartSwinger said:
http://www.forabodiesonly.com/mopar/showthread.php?t=169881&highlight=391+gears

What do you guys think about that? is that what id be looking for? Hes selling the whole rear end though right?
I was thinking i could ask him to sell me what i need if thats the right stuff?
Whats everyone think?
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Yea, the whole rear. Ask him about just the center section. Also, ask him about the U-joint size. speaking of which, what size is your U-joint? If the U-joint size's are 2 different one, a crossover U-jopint is available to fit a large to small U-joint.
 
'70DartSwinger said:
Thanks for the info guys yeah i think thats what i should do, is just buy the pumpkin
As for 4.10 i wont be doing that just stick with the 391s and yeah ill keep the 323s!
Click to expand...


Go ahead but there has been times I wished it had 4.10's vs 3.91's, like when you just lose out by 1 or 2 car lengths. With 26 inch tires @ 110 mph the engine is just at 6,000 and gets to 110 a bit quicker in most cases. Top gear pulls harder with 4.10 vs 3.91, the lower gears its a wash but when it hits 3rd gear that is when I wished it had 4.10's--most times you be way out ahead by then but if not
 
You never said what your plans are with the car.
Unless your planning alot of track time, I would run the 3.23's.
Imo, best "all around gear" out there.
Gears can get old quick.
 
Your from where they got that Stunt Driving Law. Just squealing the tires can get your car and licenses taking away for 7 days and fines of $2,000 or more. The more gear you have, the easier it be to lite the tires up--even by accident.

If you do take the car to the strip, you will hate the 3.23 gears. On the open freeways, its a great gear. 3.91--4.10 gears just drop the quarter mile et and make the car feel lighter then it is. Those gears also drop your MPG.

You might be better off staying with 3.23 expect for strip runs
 
i did my carrier myself and if i remember correctly after buying the gears and bearings and sure grip

I was at $800+/-
plus the setup (which i did myself)

after i seen the complete built center for $1200 +/- at mancini i start to wonder if i went the right road
 
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