Wich gears in my 8 3/4 RR GTX

[dutch-moparman]

Hi there
I am running 4:89 gears with a posi in my 8.75 rear. The car was set up for the strip. Like to get it more drivable on the highway.
Was thinking about 3:55, but now the questions that came up.
Wich brand should I buy? Wich bearings, and can I fix this myself.
I have a 72 RoadRunner GTX with a 8.75 rear and a 489 casing. Looked on the internet but there a too many offers to choose from. Since I live in Europe, I would like to get it wright the first time. So hopefully some of you can advise me.

kind regards from Holland

 

[74360DUSTER]

you can get richmond gears they are great. i get alot of stuff from a place called randys ring and pinion. they sell yukon gears which have been holding up great in my bb dart drag car.
i would go with the yukon or richmond gears. your cheaper gears are more likely to have a gear whine while driving.

 

[Propwash]

Here's a gear calculator that my help in picking out a ratio

http://www.richmondgear.com/101032.html

 

[74roadrunner440]

323 or 355 ar a good all around gear id actualy like a taller gear than a 323 for the strip

 

[65 Plymouth Satellite 426]

I Like And Put In The 3.55 Gears!

 

[RustyRatRod]

Keep in mind that's a pretty heavy car. I'm not sure I would go up to a 3.23.

 

[dutch-moparman]

Keep in mind that's a pretty heavy car. I'm not sure I would go up to a 3.23.

Yep, made up my mind to go for the 3.55. I am not going to race it often. The only dragstrip in Holland is only 10 miles from here, but they race three times a year. So I want to down tune the engine a bit, get rid of the 3500 stall convertor and the 4.89 gears.

thanks for all the replies, will search for Richmond gears and bearings.

 

[UKPlymouth]

Hi Dutch, do you know the guys at SixPackSpeedshop there in Holland? I'd ask them as they may even have. Asset or can get them maybe at reduced shipping.
Best wishes from the UK

 

[RustyRatRod]

Hay don't forget the 3.73 is now available for the 8 3/4 where it was not before. Might be something to think about especially if you're running a fairly tall tire.

 

[terzmo]

how tall are Your tires...Richmond have a "whine" stigma attached

 

[RustyRatRod]

I've heard that for years and It's my opinion that the "whine stigma" comes from the "mechanic" setting the gears up, not the gears. I've set gears up with mismatched ring and pinion and chipped teeth cause it was all I had and never had a sound.

 

[djais1801]

i had a 3500 stall, and 391 gears in my 8.75 rear. I got swapped the stall out for a 2200 stall, and kept the gears. I find them to be acceptable for the street, highway you're at around 3g's (RPM) at 75mph.

 

[dutch-moparman]

Hi UK
yep, I know them, nice guys, and good mechanics. But everything has a price. Know that on this forum lots of people had to make the same choices once, and wanted to get their opinion. I myself am a mechanic and can change the gears to with some tips and tricks, so I can save some money in these expensive times. Thanks for your reply, appreciate the members who take the time to help me!
Cheers
Marc

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Hi Rusty
Running 275/60/15 tyres now on a set of 8J Magnums. Got rid of the 29" MT ET tyres. So these are not so tall.

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You are right on this one, work mostly on European Cars myself. Few years ago I had to change a lot of gears on the RWD Ford Transit Vans, the first one whined, but after that one, I got them all quiet. The proper alignement from ring and pignon takes care of this problem. Haven't done this the last few years, so have to get back in the Brooks how to install the new gears.

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Hi Djais
How big are your tires? Have to make choices between drivability, power and fuel consumption. I Holland a gallon petrol costs over 10 dollar! So driving a Mopar V8 is not very funny. My RR GtX now is running 8mpg ( 3km 1litre petrol ). And this is cruising speed.
therefore I would like to go for taller gears. I am driving Mopars For many years, but rather new in the Mopar Muscle scene. Actually my second Mopar with a seriously tuned engine. Perhaps I am missing something in my quest to get my car streetable. If so, please comment.
Greetzzz from Holland

 

[djais1801]

i am running 275's in the rear, and 245's up front. i also get stellar gas mileage...about 7-8mpgs city driving.

 

[dutch-moparman]

i am running 275's in the rear, and 245's up front. i also get stellar gas mileage...about 7-8mpgs city driving.

Wow, that's a lot.

 

[Sweet5ltr]

I get around 10-12 MPG.. hmmm.. But I don't even have to touch the pedal to keep the car moving at 65mph.. Car originally got 17-18MPG with the stock 440. Best bet for fuel economy anymore is to switch over to a Gen III Hemi.. 5.7 or 6.1 would make plenty of power, and still get reasonably good fuel economy. Everyone is swapping to LS Motors in Fords and Chevys alike.. What isn't to like about an old hot rod getting 20-30MPG?! My Z06 gets 31-34MPG at 65MPH with a M12 6-speed/3.42 gears. A 3,500 pound B-Body would be shaving off over a 1/4 ton in comparison to the new challenger/charger line-up.. You could easily get better fuel economy than they do and run 87 octane.

 

[dutch-moparman]

I get around 10-12 MPG.. hmmm.. But I don't even have to touch the pedal to keep the car moving at 65mph.. Car originally got 17-18MPG with the stock 440. Best bet for fuel economy anymore is to switch over to a Gen III Hemi.. 5.7 or 6.1 would make plenty of power, and still get reasonably good fuel economy. Everyone is swapping to LS Motors in Fords and Chevys alike.. What isn't to like about an old hot rod getting 20-30MPG?! My Z06 gets 31-34MPG at 65MPH with a M12 6-speed/3.42 gears. A 3,500 pound B-Body would be shaving off over a 1/4 ton in comparison to the new challenger/charger line-up.. You could easily get better fuel economy than they do and run 87 octane.

It crossed my mind when I had the 69, but this GTX is a matching number car that I would like to keep this way. I know drivin' a big-block classic Mopar won't get very high MPG's, but like to try to get this up a bit. I won't get much fuel-economy revving the engine up to 4000rpm just to drive 60mph, so a lot could be in changing the gears. Also my 3500 stall won't help, therefore I was thinking about a 2000 stall convertor.
Could change things about the engine, perhaps you see things in my specs list that could be changed for the better.

Motor Specs:


Original steel crank – Manley I-beam steel rods, Speed Pro 10:1 pistons, chrome molly Rings, Clevite 77 bearings. Melling High volume oil pump, 7 quart baffled pan Mopar Purple cam –degreed to mopar specs, .557 lift .297 duration, double roller timing chain, solid lifters, Manley titanium pushrods, Crane gold roller rockers, Edelbrock ported RPM aluminum heads, Manley titanium valves, Victor 440 Intake, 850 Demon carb, K&N air filter, MSD pro billet Distributor, MSD 6AL Ignition, MSD rev limiter, Holley electric fuel pump and regulator, 3” exhaust with H pipe. Flowmaster 40-series. Rotating assemble was balanced and blueprinted.
Tranny has a shift kit and a 3500 stall convertor line locks on the brakes as well.

Thanks for your time sofar!
regards from Holland

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i am running 275's in the rear, and 245's up front. i also get stellar gas mileage...about 7-8mpgs city driving.

Hey Djais
Mine does this cruising 55 on the highway, city driving is worse.