gear ratio help!

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solracmopar

solracmopar

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curious to know who's running what. i recently upgraded my 7.25 to a 8.75 that has 3:55 ratio in it. I've run the car a few times and it howls like a banshee (not in a good way). The gear shop suggested running a 3:73 ratio for some more bite. Curious to know if anyone has run that gear ratio?

my driveline is a beefed up 318, lunati cam, modified swirl port heads intake etc etc. I'm running a 2500 stall converter as well. tire size is 245/60/15

any help would be great.
 
If you have a howl then a ring and pinion swap may be in order and properly set up.

Personally I don't believe you would see a huge difference from 3.55's to 3.73's.
 
solrac, ya need to Google a mph / gear calculator, and there are hundreds on the www

Depends on your rear tire size, and what you are willing to put up with for cruise RPM and mileage loss

I run 3.7x, and with my tires, 70 mph is about 3400. I don't drive this really long distances on the freeway, so for me it works out. My old 70 RR had 3.54 and it ran just exactly 3K at 70, and that little drop in RPM went a long ways
 
What are your plans with the car ?
Street,Strip,Cruiser ?
Being a 3.55 has nothing to do with howling. It was either set up wrong or just a bad set of gears.
Let us know what your plans are with the car,and we will be able to give you a better answer.
 
Johnny Dart said:
What are your plans with the car ?
Street,Strip,Cruiser ?
Being a 3.55 has nothing to do with howling. It was either set up wrong or just a bad set of gears.
Let us know what your plans are with the car,and we will be able to give you a better answer.
Click to expand...

Its mainly a street car. Before installing the rear end I had the gear shop tear it down and they warned me the gears were shot but I didn't have the money at the time to swap em out. A few months later, rear end in, it howls. So I'm for certain its a bad set of gears.

The gear shop is suggesting 3:73 for a little better bite.

I'll mainly use the car for around town and the occasional highway ride, to a show etc.
 
Could be something as simple as a bad pinion bearing.
 
solracmopar said:
Its mainly a street car. Before installing the rear end I had the gear shop tear it down and they warned me the gears were shot but I didn't have the money at the time to swap em out. A few months later, rear end in, it howls. So I'm for certain its a bad set of gears.

The gear shop is suggesting 3:73 for a little better bite.

I'll mainly use the car for around town and the occasional highway ride, to a show etc.
Click to expand...

For around town,the 3.73 gear would be fine,but a different story out on the highway. IMO,you will get tired of them real fast on the highway.
For what your doing,my vote would be to stick with the 3.55 or even go to a 3.23.
For a really good gear set,at a great price,look up "Motive" gear sets.
 
Here is what I came up with. Looks pretty close to me.


3.55 / 3.73

2500 RPM 54.47 MPH 51.84 MPH

3000 RPM 65.37 MPH 62.21 MPH
 
Johnny Dart said:
For around town,the 3.73 gear would be fine,but a different story out on the highway. IMO,you will get tired of them real fast on the highway.
For what your doing,my vote would be to stick with the 3.55 or even go to a 3.23.
For a really good gear set,at a great price,look up "Motive" gear sets.
Click to expand...

I appreciate that advice. Not sure how much more of a gain I'd get around town with 3:73 but if it got annoying at highway speeds I'd be stuck. Maybe 3:55 is the best all around gear.
 
Johnny Dart said:
For around town,the 3.73 gear would be fine,but a different story out on the highway. IMO,you will get tired of them real fast on the highway.
For what your doing,my vote would be to stick with the 3.55 or even go to a 3.23.
For a really good gear set,at a great price,look up "Motive" gear sets.
Click to expand...

Didn't realize Motive was that good. I saw the price on Summit and wondered how good the quality was. Thanks again..

http://www.summitracing.com/parts/mgr-c887355m
 
The howling is due to the lash being set wrong. Hopefully, this hasn't been going on so long that the ring and pinion are not usable.
 
You didn't happen to get the number of your current back lash did you? There are alot if things to consider when setting it. If the rear came out of a 4 speed car it's probably going to be set alot tighter than a auto which may cause the howl. I know you probably have alot of faith in this shop but it never hurts to double check.
 
once a rear end is set up unless things have changed since I was doing them which I duwt cus i'm sure they arent heat treated as depe because the japs are making every thing now those bastards ?can I say that I know theres a lot of children on here now.and the last one I did was in the 70s...that being sead she eeeeeeeeeeew ...damit boy OK here we go.there is nothing you can do to save them that I know of..people and things a lot smarter now.howl till the end of time.......or check with rob I think hes my age rusty rat rod I know him as.......Artie:coffee2::coffee2::coffee2::coffee2::burnout::burnout::burnout::newb::newb:
 
Ended up buying a new set of Motive 3:55 gears and bearing kit. This is the first time I've pulled a chunk from a 8.75. Now I get why they so niiiice:cheers:
 

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