2.76 Diff Ratio

[DJCUDA]

Hi not sure if this question has been asked previously, does anyone make NEW 2.76 gears for an 83/4 489 Diff.

Also if I was to change to 3.55, (because this all I have been able to find from most suppliers) will these fit in my housing, some research I have done has said they won't fit because they are too big.
Cheers.

 

[Adam]

3.55s will definitely fit in an 8 3/4, 489 carrier. I do not know about new 2.76 gears..

 

[DJCUDA]

Cheers for that Adam, I have since found 3.23 ratio gears made by Yukon, these are sold by Summit so I would hope they too will fit in a 489 housing.

 

[DetMatt1]

Those will fit too. I think all 8 3/4 ring gears will fit in that housing.

 

[TC_Cuda]

I know there was a good posting that had a link to good info on 8 3/4 rear end but, I cant locate it, maybe someone can point it out but,

my understanding in that you can fit 2.76 all the way to 5.13 in a 489 housing. I have 3 with, 2.76, 3.23 and, 3.55 and soon one with 3.91 and all are 489 housings

I also have a 4.56 but that is in a 657 housing ( yes I know it's the weak one but, it held up just fine for me on the street )

also are you going to build it or have it done... if your having it built for you, just let them get the gear for you as they will make sure it is the right one

 

[DJCUDA]

Thanks everyone, that's good information.

I am having the diff done by an expert, I live in Australia and there are not too many Diff specialists in Adelaide that know much about the 8 3/4, from what I have been told it appears we did not have them in any Chrysler cars here?. The Company building the diff has already made some inquiries with other diff specialists (they all seem to know each other) and he was told that other ratios may not fit, but were not totally sure, hence me asking the forum.

Also I was quoted over $600 for a crown wheel and pinion and another $275 for a master rebuilt kit, that does not include labor to dis-assemble/assemble, I reckon the all up quote is going to be around $13-$1400. I can source the parts delivered to Australia for $700 Aussie which is pretty good, Summit only want $96 US for postage, YearOne want $276US, but they don't have the 3.23 ratio.

So it looks like the 3.23 will be the go, I did find the 2.76 a little sluggish off the line, I am only running a 318, but have had the heads slightly ported with large intake and exhaust valves, I am also running an upgraded camshaft and a 4 barrel carby and manifold.

 

[Steve340]

Nitro also make diff gears for the 489 casting. I have their gear set in my car and it is good.
Nitro has an Aussie dealer.

 

[Cazbah362]

DJ - Doctor Diff here in the States has a large supply of 8 3/4 items: DoctorDiff Drivetrain Components

 

[Steve340]

489 casting gear sets are made in either 10 or 29 spline.
Better find out and match to your driveshaft pinion.

 

[DJCUDA]

I found the Nitro Agent here, (Black Diamond Auto Dismantlers) he is actually only 40 minutes from where I live in Adelaide, interestingly I did not know he was an agent, guess I will be calling him first thing Monday.

Thanks for the information, I'll keep you posted on how I go.

 

[70Hardtop]

Hi mate, I'm in Aust too and having trouble with my 8.75. I took mine to a diff centre here in my city, "Diffs is all they do" they say and been the game 30 years. But can you believe he had never heard of the Chrysler 8 3/4 ! Needless to say I didn't get any work done there. The master rebuild kit should only be about US$120. You can get most things from the States that you need. I looked at the Nitro also but was going to be all up over A$1200 with postage. I have decided to rebuild mine, Doctor Diff sells everything required. Summit sell sets of crown wheel and pinion sets for good ratios and shipping is very reasonable considering the weight. Not sure why you were told that some ratios will not fit, they obviously didn't know much about their subject. 2.76 is WAY too tall for a 318. Would be not too bad in a performance 440. 3:1 and 3.23:1 are the best range of ratios for the street and good all round set. I am using that ratio in my Challenger 340. I also have a 3.55 set but that is going behind a Tremec 5 speed.

 

[DJCUDA]

Thanks Dart77, It looks like you've done some homework on this, I too got the same replies from a couple of "diff specialists", what's an 8 3/4 mate???, but the bloke doing the diff rebuild for me knew what an 8 3/4 is and has done them before, but not changed ratio's, when he inquired with his supplier (another diff specialist) he was told that other ratio's may not fit so he asked me to do some researching and find out. I reckon Summit is the way to go, I asked their Tech People about the ratio's and whether they would fit in the 489 housing before I asked the guys on this forum, they said they don't have the info and are inquiring with Yukon, they said they will get back to me shortly. I would have been happy with 3.55's if the 3.23 was not available, I'm not planning on doing much interstate runs so I reckon they should do the job, like I said earlier I found the 2.76 sluggish off the line.

Just want to say thanks to everyone for helping me out.

 

[70Hardtop]

Yeah DJ, it's only when you have a problem or are modifying something on the car that you start to learn so much in a short time. Just spoke to a fellow a few days ago with a Cuda, said he ordered a gear set from Summit, reckoned it only cost him US$30 for shipping. Seemed a bit too good to be true to me but he was sure about that and he's no dummy. Doctor Diff carry the rebuild kits, so do Mancini Racing I think. I had a 3.23 in my Charger 340 and even that I felt was revving too much at 100km/h. But up to 100km/h it was amazing for all round performance. I think 3.55 would just be too high revving if doing much over 80k's, unless your engine was comfortable sitting over 3500rpm a lot. I did an interstate run in my Chal and for that I put in a 2.6:1. Of course it didn't accelerate very well but it was an amazing cruise ratio, I could sit on 90 mph all day and the engine was only doing about 3300. Good luck with your diff.