We just bought a new Sure-Grip for the Challenger.

[SteveSS]

The '71 Challenger has a 408 Stroker with an 833 4-speed. It came with an open 2.76 open diff. We somehow happened onto a Sure-Grip 3.91 and ran that for a while. It blew up eventually and we went back to the open. That started leaking really bad so I bit the bullet and ordered a new/rebuilt Sure-Grip with 3.55 gears. I remembered a guy in Arizona was rebuilding these so I tracked him down. His name is Tom Hild in Lake Havasu, AZ. It was $1450 plus $150 shipping. He builds these neat little crates for shipping. I wired money today and he just sent me a picture of the unit completed and packed in its container. None of these diffs are cheap but I thought this guy was reasonable.

I'll let you know how it feels and sounds once it's in.

 

[road robert]

The '71 Challenger has a 408 Stroker with an 833 4-speed. It came with an open 2.76 open diff. We somehow happened onto a Sure-Grip 3.91 and ran that for a while. It blew up eventually and we went back to the open. That started leaking really bad so I bit the bullet and ordered a new/rebuilt Sure-Grip with 3.55 gears. I remembered a guy in Arizona was rebuilding these so I tracked him down. His name is Tom Hild in Lake Havasu, AZ. It was $1450 plus $150 shipping. He builds these neat little crates for shipping. I wired money today and he just sent me a picture of the unit completed and packed in its container. None of these diffs are cheap but I thought this guy was reasonable.

I'll let you know how it feels and sounds once it's in.

Greetings SteveSS:

So how does it feel and sound?

You must be surprised getting a reply more than 2 years later - you're the only mention of Tom Hild... It turns out that Tom Hild called me last night after Cass (DoctorDiff) referred him to me (he is out-of stock no lead time) and I e-mailed him the other day about a third member. We talked for 1hr 45mins! Quite the ultimate car guy and very interesting too and he's 71 and still going strong!

I decided to swap my 3:91, I love it came on my 383 4-speed road runner owned for 5 years. I always "avoid highways" because I prefer that but it's becoming scary noisy > 55mph and sometimes I need to jump on the highway to get somewhere! And I want to do the forbbodiesonly Power Tour in 2 months and that's a lot of miles (~1800 round trip) with the 3:91. I was thinking 3:23 but after speaking with Tom decided I would be happier with 3:55.

Cass said to have Tom "build a third member around my Sure-Trac differential" (8 3/4" Helical Gear Sure-Grip ("Sure-Trac II") $595 on DoctorDiff site - expen$ive so I decided to go for it and to make things easy buy (Axle Pkg Custom Length Mopar 5X4 1/2" Bolt Pattern (pair)) with the green bearings installed and a new pair of inner seals too. I do not want to deal with replacing worn bearings cutting off/pressing on new ones for the $305 it will be plug & play axles/bearings swap.

The price today is closer to $2K plus shipping (Tom buys parts from DoctorDiff) his price for (8 3/4" 489 Case Third Member) is $1495 but he ain't got none:
Mopar 8 3/4" (8.75) 489 Case Third Member

road robert

 

[RJ Squirrel]

I put 3:55 in my Roadrunner I built from Dr Diff parts and very happy with it. A little hi-revving on the hiway but not too bad locally. I am looking for a 3:23 open diff for any future long trips.

 

[Nutso]

Thanks for sharing the info! It’s great to get actual experience.