Anyone make a Custom Ring and Pinion for 8.75??

-
Status
Not open for further replies.
7

72DMag

Well-Known Member
Joined
Oct 21, 2019
Messages
1,171
Reaction score
257
Location
Pittsburgh
Hi guys, direct connection use to offer a 5.57 gear ratio for the 742 8 3/4 rear end. I contacted all the big suppliers, richmond, strange, us gear, yukon and I was told pretty much the same thing by everyone. Either they can't do it or they will need an order of 50 or more to do it.

So is there anyone out there that can remake this gear ratio??
 
72DMag said:
Hi guys, direct connection use to offer a 5.57 gear ratio for the 742 8 3/4 rear end. I contacted all the big suppliers, richmond, strange, us gear, yukon and I was told pretty much the same thing by everyone. Either they can't do it or they will need an order of 50 or more to do it.

So is there anyone out there that can remake this gear ratio??
Click to expand...

Can you run a 5.13 and a little shorter tire?
 
72DMag said:
Hi guys, direct connection use to offer a 5.57 gear ratio for the 742 8 3/4 rear end. I contacted all the big suppliers, richmond, strange, us gear, yukon and I was told pretty much the same thing by everyone. Either they can't do it or they will need an order of 50 or more to do it.

So is there anyone out there that can remake this gear ratio??
Click to expand...
I either have one or it is one that I tore the teeth off of many years ago. I used the 8 3/4 over 30 yrs and only tore up 2 units. Both resulted in stripped gears. I felt very lucky because I was using up to 650hp. I'll look next trip to the shop and if I still have one I'll let you know.
 
Get ahold of Dr Diff. He doesn't have that ratio listed on his site but he may know who has one.
 
@Blucuda413 I can shift lower and lower my et. But I do have the hp and tire size set the way I like right now. Also, that's my concern is that if something goes wrong years from now and I need another 5.57 gear how to get one. Guess I should start looking for old used or nos stock ones now cause it sounds like suppliers will only do a bulk buy.
 
I think there use to be a 5.38 for an 8 3/4', but still hard to find. With typical .2 steps in ratios - 4.86 -5.13 - 5.38 - 5.57, etc. I don't think you could get a whole 'step" just by using a 1" or so shorter tire. You can figure it out more accurately with a gear/tire diameter/rpm formula.

Class racers sometimes get together for a volume purchase on custom ratios.

Dana 60 ratios might be easier to find and the efficiency often makes up for the added weight. Good insurance for a Torqueflite.
 
@RustyRatRod Maybe a dana someday but it is nice to have the third member. I have 2 setup. 1 for 1/4 mile 1 for 1/8mile.

@Locomotion yes they did make a 5.38 too. A member on here offered it to me but its just not what I'm looking for.

Correct me if I am wrong guys but didn't they (Ma mopar) make the 5.57 for both the 742 and 489 case?? I guess if I find one for the 489 I can just get that case. I just hate doing the crush sleeve eliminator.
 
72DMag said:
@RustyRatRod Maybe a dana someday but it is nice to have the third member. I have 2 setup. 1 for 1/4 mile 1 for 1/8mile.

@Locomotion yes they did make a 5.38 too. A member on here offered it to me but its just not what I'm looking for.

Correct me if I am wrong guys but didn't they (Ma mopar) make the 5.57 for both the 742 and 489 case?? I guess if I find one for the 489 I can just get that case. I just hate doing the crush sleeve eliminator.
Click to expand...

I recall 742 and 489 cases having similar ratios, but an old gear catalog or Mopar Performance book/manual would have more info. I thought about swapping to shorter tires for 1/8 mile, but as mentioned, the difference wouldn't have been a lot.

Lower ratios often mean smaller, weaker teeth.
 
72DMag said:
@RustyRatRod Maybe a dana someday but it is nice to have the third member. I have 2 setup. 1 for 1/4 mile 1 for 1/8mile.

@Locomotion yes they did make a 5.38 too. A member on here offered it to me but its just not what I'm looking for.

Correct me if I am wrong guys but didn't they (Ma mopar) make the 5.57 for both the 742 and 489 case?? I guess if I find one for the 489 I can just get that case. I just hate doing the crush sleeve eliminator.
Click to expand...

There's always a 9".
 
Thanks guys I'll start searching the forums to see what I can find. Rusty a ford rear under a mopar!!:wtf: lol Just messing with ya! Sad that the 8.75 gets no recognition imo
 
72DMag said:
Thanks guys I'll start searching the forums to see what I can find. Rusty a ford rear under a mopar!!:wtf: lol Just messing with ya! Sad that the 8.75 gets no recognition imo
Click to expand...

Well........I'm certainly not defending the lack of Mopar parts, BUT the 8 3/4 hasn't been made in how long now? Plus, swaps to Danas and 9s are very common. It's kinda like it always has been. Mopar has always been the bottom of the list for aftermarket support.
 
It took me forever to sell my 5.57s. They were in a 742 case with a clutch type sure grip. I had to split them apart to sell separate. Case, gears and unit. Kim
 
72DMag said:
Sad that the 8.75 gets no recognition imo
Click to expand...
I think, IMO, that this is the way now but not yesteryear. When the 8-3/4 was being made and a few years thereafter..... the support was there. As HP & Tq were increased over the years as we learned how to make more and more power, the 8-3/4 just couldn’t hold up vs a DANA or a Ford 9. So the swap was done and popularly waned. And this support.

Many years before that, the rear end of choice was from an Oldsmobile. Where are they now?
 
Still interested in the mopar 8:75 gears The dana is too heavy and there is no way a phord in my mopar will ever happen Ill take all 50 gears sets before a phord diff goes in my mopar ps:we have rules for class 400hp max
 
I tried to send you a message. Let me see what I have at the shop in the morning. I might have one out of old Dodge truck.
 
moparfourever said:
Still interested in the mopar 8:75 gears The dana is too heavy and there is no way a phord in my mopar will ever happen Ill take all 50 gears sets before a phord diff goes in my mopar ps:we have rules for class 400hp max
Click to expand...

Just wanted to offer some insight that is sometimes overlooked when comparing the weight of an 8 3/4" and a Dana 60. The more race oriented modifications are made to both, which usually lighten them, the closer they are in weight. (With 35 splines, axles will be pretty much the same. I don't know if gun drilled 40 spline axles in a Dana 60 would be lighter than 35 spline gun-drilled axles in an 8 3/4)) But going from a Sure-Grip to a spool, you'll shave a lot more weight off of a Dana 60 than an 8 3/4 because the Dana part is bigger and heavier to begin with. Same with lightening the ring gear. The Dana 60 is also more efficient (takes less HP to turn) than other HD rears, including the 8 3/4. (GM 12 bolt is most efficient while Ford 9" is the worst. Not a lot, but differences are there.) This makes up for some, if not most of the weight as there have been several class racers who switched and didn't see any loss in ET once weight was adjusted (Back to minimum class weight.) to make up for the extra Dana 60 weight. It also puts the weight where it will do the most good for traction! Then there is the extra durability that will help preserve a torqueflite trans.

I wish I remembered the exact weight difference when I switched the rear in my Aspen wagon. I'm pretty sure it was less than 60 lbs, but more than 40. But I was confident enough in the benefits vs the small weight increase to do it, even with a low compression 360. I never established a consistent baseline to notice if there were any performance changes due to the switch.
 
@Locomotion Good write up!!! and I agree that the weight difference if done correctly is negligible. For me the 8 3/4 is better and easier because tracks around me some are 1/8 mile some are 1/4 and sometimes those 1/4 mile tracks have 1/8 mile races during the season. Therefore its just alot easier to switch third members than being much slower in the 1/8th with the gears for 1/4 races. Yes switching gears in the dana really isn't too bad. But to do that 3 times throughout a season. I'll pass
 
72DMag said:
@RustyRatRod Maybe a dana someday but it is nice to have the third member. I have 2 setup. 1 for 1/4 mile 1 for 1/8mile.

@Locomotion yes they did make a 5.38 too. A member on here offered it to me but its just not what I'm looking for.

Correct me if I am wrong guys but didn't they (Ma mopar) make the 5.57 for both the 742 and 489 case?? I guess if I find one for the 489 I can just get that case. I just hate doing the crush sleeve eliminator.
Click to expand...
Zoom offered one also [5.57] I bought a nos set up last year from a member
 
Sorry using this in my 66 Valiant , SSBARRACUDA in Tampa just put this together for me
I have a new complete 489 [ spooled 4.56 ] set up for sale
 
Here is factory part numbers maybe they can aid in search process
Be cool to find some old US stock out there !

20210109_105816.jpg
 
@72DMag i agree we oval race and switching gears every week is a pain. We have to run stock parts so the 8:75 is required as well people do crazy **** to shave 5 pounds.
 
Status
Not open for further replies.
-

Back
Top