8.75" Differential & Gear Questions

[Ghosty]

Got a 8 3/4 rear-end with 4.10 gears. The code is: 2881489, translated as a 489-Case, built between 69-74.

1st) The few sites I've looked at all say there should be a big "9" stamped on the left side. This one has a "Y" on the left, not 9. What does that mean? Just curious, before I order gears.

2nd) How about brands: Yukon (from Randy's or ?), Motive, Strange, Richmond (Summit), & USA Standard (Randy's & eBay). Range from $200 for most to $400 for Yukon. Seems most people are happy with any of these? Going to a 3.55. Do I need to order the complete install kit with all the small components, or just the ring & pinion set? The diffy is already rebuilt with very few miles. A shop is doing the swap for me.

3rd) How do you feel about a 4WheelParts type shop? The svc. mgr. says they've done a TON of rear-end gear swaps for trucks incl. Mopar and would be very comfortable doing this. But I know some people will think this might not be the best idea. Thoughts?

It's a 440, 727-auto w/ Hughes 3500 converter. I'd like it to drive nicely on the highway without winding out like a Singer sewing machine like it does now, lol. Not much drag-racing except maybe Mopar wknd or club days at Bandimere.

 

[themechanic]

Contact DrDiff.

http://www.doctordiff.com/

 

[67 coronet]

you are prob better off with a diff shop rather then a 4x4 place.many times they can do rear diffs there,but are not that experienced in them.as far as gears go,only advise i can give is richmond make noise because of the gear cut angles.i run em,but i cant hear over my motor anyhow.if getting an install kit,check with the shop first.they may be able to supple your berings cheeper then getting them yourself.489 case is all you need to get right stuff.

 

[Grabinov911]

Hey Ghosty I just installed a brand new 3.55 ratio 489 rear end in my 1970 Roadrunner - got it from Dr. Diff at the Mopar Spring Fling in Southern California. The "Y" on the case is the same as my new one. Yukon puts a "Y" on the case where the factory put the "9", so that is actually a Yukon gear case. My new rear end uses all Yukon parts. See my thread on the rear end install for details. It's called something like "You Want me to What?"... You can find it under my screen-name...

 

[RustyRatRod]

The Y and 9 mean nothing as far as the type of case. If the last three digits are 489, it's a 489.

 

[67Satty]

The other thing to keep in mind is that some 489 cases are 29 spline and some are 10 spline. Most of the gears available these days are for the 29 spline.

Dr. Diff has good prices on the gear sets meant for 29 spline and he can also sell you a yoke to convert from 10 spline to 29 spline if you need it.

To find out if you have either a 29 spline or a 10 spline 489 case here's a quote from Dr. Diff on the Moparts tech pages:

"If the pinion nut takes a 1 1/8 socket, it is a 10 spline. If the pinion nut takes a 1 1/4 or 1 5/16 socket, it is a 29 spline.

-DoctorDiff"

I might be a buyer for your 4.10 gears if they are quiet as I want to get rid of the noisy 3.91s I have right now. Let me know.

 

[tallhair]

A few months ago I did quite a bit of research and talked to Randy's and Dr Diff. I recommend buying the Yukon gears or genuine spicer gears.

They have more machining steps and the gears will be quieter according to Randy's and Dr Diff. Lesser priced gears have less machining steps and are more likely to whine.

I'm sure folks have bought richmond and others and had no problems though. Just passing along what I was told about the price differential.

 

[67Satty]

A few months ago I did quite a bit of research and talked to Randy's and Dr Diff. I recommend buying the Yukon gears or genuine spicer gears.

They have more machining steps and the gears will be quieter according to Randy's and Dr Diff. Lesser priced gears have less machining steps and are more likely to whine.

I'm sure folks have bought richmond and others and had no problems though. Just passing along what I was told about the price differential.

Do you know if the ones made by Strange are noisy too? Jegs seems to be the only place that has a 4.30 ratio available for the 489 case with the 10 spline and they are made by Strange.

 

[tallhair]

No I don't have any experience with them. Just passing on what I found researching so I'll defer to Meep, Cranky, Budnicks, etc as they and others have hands on experience.

 

[Ghosty]

Thanks for all the good info guys! Interesting, didn't know it was a Yukon case. I can't wait to talk to the diffy and trans guy that built them. He'll have the details. Dunno if those are Yukon gears inside and whether it's a 10 or 29-spline. I'll find out. I definitely would prefer less noise. My buddy's T/A had a Moser rear and it whined almost as loud as an electric fuel pump.

Grabinov911: I did see your thread actually awhile ago, got some good info outta there, thx.

67 coronet: I'll have to look around for a reliable diffy shop here in Denver. I want the install/align & shimming done proper the first time.

 

[Supershafts]

Do you know if the ones made by Strange are noisy too? Jegs seems to be the only place that has a 4.30 ratio available for the 489 case with the 10 spline and they are made by Strange.

USA or US gear makes the gears for Strange

- - - Updated - - -

A few months ago I did quite a bit of research and talked to Randy's and Dr Diff. I recommend buying the Yukon gears or genuine spicer gears.

They have more machining steps and the gears will be quieter according to Randy's and Dr Diff. Lesser priced gears have less machining steps and are more likely to whine.

I'm sure folks have bought richmond and others and had no problems though. Just passing along what I was told about the price differential.

Motive is richmond and has been for a few years now. Motive, Nitro*, Dana*, US Gear*, Precision*, Superior, Yukon, G2, Sierra and quite a few others i have installed numerous times over the years, none of them made noise.
There are the china issues and the china pirated **** out there that suck, and for shops like me cause more time to get right, but noise is 98% of the time the person who believes they understand the job at hand enough and really does not.

67salty, a 3.91 is not a noisy gear ratio, when you get to the 5.8 and up they can make noise at higher speed

 

[Ghosty]

To find out if you have either a 29 spline or a 10 spline 489 case here's a quote from Dr. Diff on the Moparts tech pages:

"If the pinion nut takes a 1 1/8 socket, it is a 10 spline. If the pinion nut takes a 1 1/4 or 1 5/16 socket, it is a 29 spline.

-DoctorDiff"

I might be a buyer for your 4.10 gears if they are quiet as I want to get rid of the noisy 3.91s I have right now. Let me know.

Thx , got the same info here: http://www.forabodiesonly.com/mopar/archive/index.php/t-191394.html

When I find out what gears are in it, I'll let you know on possibly selling them.

USA or US gear makes the gears for Strange. Motive is Richmond and has been for a few years now.

Noted.

Motive, Nitro*, Dana*, US Gear*, Precision*, Superior, Yukon, G2, Sierra and quite a few others i have installed numerous times over the years, none of them made noise.

Good to know, thx. I've also read noise factor is mostly (but not always) in how carefully and properly they're setup (backlash, shim, etc.) Which also makes me lean away from a 4Wheel shop doing mine.

 

[Supershafts]

mostly[/I] (but not always) in how carefully and properly they're setup (backlash, shim, etc.) Which also makes me lean away from a 4Wheel shop doing mine.

Noise is 98% of the time all on the builder. If the 4wheel shop is driveline experienced then it may be ok, or you may just want to look for a specific driveline shop that specializes in driveline work.

Ask around and see what some people say.
.

 

[Ghosty]

I found two excellent recommended Diffy guys that even specialize in Mopar rear-ends. Unfortunately both are 75+ miles away. If I can't find a good guy in the Denver Metro area, I'll take it to one of them.

The car wraps up to 4k or so RPM's at 75mph, it's a 440-auto. Do you see a problem (besides noise/gas) with driving that far on 4.10 gears in 90+deg. heat? Has a nice Champion radiator, dual electric fans, and a small trans cooler. I just haven't had an old BB V8 in so long, so everything worries me now, lol.

 

[67 coronet]

i would drive 60 or 65 and save the wear and tear.just watch the temp guage.

 

[Supershafts]

If it doesn't run hot then you'll be fine, or you can just take a ride at 65

 

[Ghosty]

Got tons of recommendations from Colorado USP heads-up racers, mostly for FrontRange Driveline here in Englewood. Only about 15 miles from my house so I'm good. The other Mopar diffy expert is in Boulder. Got backups in Loveland, Greeley (also specializes in Mopar), and ColoradoSprings. If any Colorado folks want their names and contact info, hit me up!

Before I buy gears I'm pricing out 4spd and 5spd trannies. With a (expensive) 5spd, might not need to change my rear-end. Still researching Brewers, eBay, Passon, Keisler, Tremec, AmericanPowertrain, Mcleod, etc...

 

[Roadbird]

That Y might denote Yukon gearing. I could be wrong too.

 

[Ghosty]

Thanks. This Charger tranny thread (and many others) keeps me guessing on the best route to go with my trans. I'll drive the 727 for awhile and see how bad I miss a 4spd, or not. Most of my life I've never had an auto except in my dailydriver truck...

http://www.dodgecharger.com/forum/index.php?topic=78754.0

 

[idrivemopar]

Got tons of recommendations from Colorado USP heads-up racers, mostly for FrontRange Driveline here in Englewood. Only about 15 miles from my house so I'm good. The other Mopar diffy expert is in Boulder. Got backups in Loveland, Greeley (also specializes in Mopar), and ColoradoSprings. If any Colorado folks want their names and contact info, hit me up!

Did you also talk to John at Mopar Madness in Eaton Colorado?