Value of 8.75/3.91/742

mopartaz · December 26, 2019, 10:42:08 AM

Anyone know what a rebuilt 7.42 case, 8.75 w/ 3.91's are going for these days? thanks

1 Wild R/T · December 26, 2019, 10:43:27 AM

with or without sure grip?

mopartaz · December 26, 2019, 10:57:46 AM

Clutch pack sure grip, new gears etc

Rich G. · December 26, 2019, 03:55:36 PM

I'd say 4-5 hundred.

RUNCHARGER · December 26, 2019, 05:36:04 PM

Could be $800 I think, adding up the cost of the parts.

Rich G. · December 26, 2019, 05:40:51 PM

I would think the 489 case would be worth more. Just from what I've seen at swap meets.

Katfish · December 26, 2019, 06:13:14 PM

I sold a 3:55 for $350 not too long ago locally.
Shipping is the problem with these.
With yours being rebuilt, I'd say $500.

1 Wild R/T · December 26, 2019, 06:19:21 PM

Quote from: RUNCHARGER on December 26, 2019, 05:36:04 PM
Could be $800 I think, adding up the cost of the parts.

I tend to agree.... We were paying 4-500 for a good 742 case 3.91 gear clutch style back in 1990....

JMO but I'd pay more for a 742 than a 489....

RUNCHARGER · December 26, 2019, 06:37:11 PM

Me too: Faster to setup with no crush sleeve to deal with. I still like 3.91 too, either with an OD or without. Kind of depends on who set it up I suppose and how clean everything looks.

nsmall · December 26, 2019, 08:50:20 PM

If the sure grip is newer I am thinking more like $800.

Bossgold · December 28, 2019, 04:25:16 PM

I think any where from $ 400 to $ 800 cause it really depends on information like where did it come from (truck, AAR, Challenger) and miles as well as shape of the gears. I think a really nice case 489 or even 742 that has verified low miles, clean gears and came from a car like an AAR or T/A vs a truck is worth the top end. 3.91 OEM cases in good shape with original low miles are hard to find. Trust me...my car was very clean except for the original 489 case that was sitting in a carton. When I picked it up a lot of the gear teeth fell out. So I found a OEM replacement 3.91 489 sure grip in nice shape after looking a year.

1 Wild R/T · December 28, 2019, 05:04:23 PM

742 never came in a Challenger or a Cuda they were phased out in 68... Mostly 489's and a few 741's in Challengers & Cuda's....... But the 742 is still the heaviest duty 8.75.... Why would it matter whether it came from a car or a truck? It's the exact same unit....

Bossgold · December 28, 2019, 06:31:54 PM

mopartaz, sorry let me try and be more clear.....

742 cases were from 1961-1969 and were phased out for the 70 year. Therefore AAR's and T/A's came with 489's. 742's have larger bearings(1 3/4 stem) and 489's have the tapered thicker Pinion shaft (1 7/8) instead so there are discussions on which is better and/or stronger - DRAMA

My AAR originally came with a 489 case and 3.91 gears. Unfortunately the previous owner blew it up and swapped out the Third member with a 742 case with a 3.91 which was not Original to my car or to the AAR's or T/A's. He either could not find the parts for the 489 or he felt the 742 was stronger and since he blew up the Original 489 I'm betting he chose a 742 case

Having the Original 489 case I went looking for parts to repair the third member back to original. I started looking for used/NOS 3.91 gear sets for the 489 but that turned out to be challenging since most in the cars were pretty beat up and worn - 3.91 seemed to be harder to find than other ratios.

Hence why Steve's Musclecars, Wildcat and Doctordiff recommended that I consider trying to find a D100/W100 Truck 3.91 set - Since they are the same case. Also, Trucks might not be as beat up as the "high weight/medium horsepower applications through high weight/high horsepower applications" AAR and T/A's that were Drag raced in the day. Because that's actually how my original 489 was blown up.

So back to the point of the question- I just paid $ 700 for an original 30,000 mile AAR 489 'crush sleeve' third member 3.91 with Original sure grip - pulled out of an AAR back in the 80's. I looked at everything for a year. To rebuild the Donor 489 with new bearings/seals and inspect the sure grip (should be fine and not need replacement) was $ 300 including cleaning case metal to original bare condition. Now its not a 742 3.91 but I think that will at least give you a ball park of what to expect. BTW - add in shipping to the cost cause its a fortune and I would recommend you buy/drop ship a differential storage case that you can find at Summit racing if you plan on any shipping.

I checked on my Original Case from my car to do a complete rebuild using motive gear C887391L-10 3.91 Ring set and a Powertrax Grip Pro GT388730 (replace the Sure Grip unit) with bearings/seals ran about $950. To rebuild/install into my Original 'Date Correct' 489 add the $ 300 to $ 400 depending.

So I hope that clarifies my original post......and I will be pulling out my current 742 third member to sell.

js27 · January 06, 2020, 11:38:54 AM

If my memory servers me right-the 742 case came with forged steel caps while the 489 case came with cast caps. When I raced my 67 GTX I had a 489 case with 4:56 gears and 10.5 " slick with a 4 speed and blew the caps right off the carrier. I took the stock 742 case that came in the car added a set of 4:88 gears same slicks and trans and never had another problem.
JS27