Some 4.56 gear questions!!

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Dusterdude72

Dusterdude72

IN MOPAR MUSCLE MAGAZINE
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Ok everyone, back when I bought my duster...just before I got it the kid had the 489 8 3/4 rear rebuilt and SAID it had 4.10 gears in it.

well....

I need a speedo gear because i don't have one so I figured for the heck of it I would check to make sure it was 4.10 gears.

NOW...I think I calculated this right...so i will run it passed everyone for there input.

I put a peice of tape on the drive shaft and a peice of tape on the tires.....the drive shaft turned roughly 4.5 times to 1 tire revolution......x that by 10 and I get 45 drive shaft revolutions to 10 tire revolutions.

now I am sure since I was not using my (precision masking tape) that I could be off by .6 on my revolution .....which would give me 45.6 ....devide that by 10 would give me 4.56.

so am I right in how I came up with this? and would you all agree that 4.56's is the gear I have with the number of rotations I came up with?

and also ....who sells speedo gears in the 4.56 range for my 904 in my duster?

year one stops at 4.10's and summit does not seem to have them either.

Thanks in advance everyone!
 
Is it a open or sure-grip? If you have an open rear you double the number, suregrip you don't double the number.

check ebay for the speedo pinion. I picked up for a lot less than what yearone wants.
 
I put a dab of spit on the top of the tire,then some more spit on the quarter panel in line with the spit on the tire.I turn the tire slowly and count 1/2 revolutions of the rear yoke until the marks line up again.1/2 1. 1/2 2 1/2 3 etc.This crude method should get ya real close.
 
Personally,I don,t think you,ll like 4.56,s in a street car.You might want to swap them out for a lower gear(3.55 or 3.73,s)while the car is idle.JMO.
 
I think you got it right there dusterdude. And I think he mentioned that it is a suregrip so it sounds like you got yourself a steep one. Not street gears for sure!!! I'm with the crowd that says look for something in the 3's, I think you'd be much happier. Good luck with the Duster, sounds like you're coming right along after that little financial setback about a month ago. Geof
 
well im still not exactly financially stable BUT I have been able to get some things done with the duster and bills are paid....so thats ok with me lol.

as for the gears being to high.....I wont take the duster on the highway and would rarely take it above 55 mph as it would be a city and country road cruiser....I like the fact of the tall gearing for going to the strip but then again I don't know how often I will go to the strip with it.

I think I will leave this set up in there and when I finally get the duster road ready I will drive around with it for a bit and if it keeps my rpm's up there to much then I may swap out for a different set of gears.

thanks for the opinions everyone I appreciate it .

sorry if I got everyone confused with my gear ration formula LOL..... in basic terms I think that this is the formula....

I think 1 tire revolution = 4 1/2 .6 (4.5.6) x 10 = 45.6 (pinion revolution) / 10 = 4.56 ratio .....anyhow , I am no math wizz but I am pretty sure thats the right formula lol.

anyone know where I could get a speedo gear for this size gear? ( I forgot to look at my tire size but I can check later) just trying to find someone that even carries anything in that size range.

Thanks all
 
you'll need the tire size in order to pick the correct pinion gear. I hope you have tall tires with those gears
 
harryhood said:
you'll need the tire size in order to pick the correct pinion gear. I hope you have tall tires with those gears
Click to expand...


If you read above you will see I mentioned I ahave yet to go out and check my tire size ....I just wanted to see if anyone knew of a place that even offered speedo gears in the 4.56 range and if so then I can narrow it down with my tire size.

and yes I have tall tire...I think it measures out to about 28 inch's tall? not 100% on that but it has some meats on it.

Im going to run out real quick and grab the tire size and Ill let you all know
 
275/60/r15 , they measure out to about 27 inchs tall...they are BFG drag radials
 
looks like you need a 40 tooth Orange or 43 tooth Blue pinion. I'd try ebay
 
I've seen a lot of inquiries about speedo gear availability lately so when I'm at the Nats this weekend I'm going to get the contact number of the guy who always has bins full of speedo gears for sale. He has a chart to correspond all of your information to insure that you choose the right gear for your application. I'll post his contact information in a thread for all to see and use here when I get back. Hows that y'all??? Geof
 
As for which one you need, my chassis book is in storage and I have no idea which box. If you have access to a MP chassis book, with your tire height and gear ratio it will tell you which speedo gear you need. If you can't find the correct one on ebay, go to one of the big car shows like Carlisle or MOPAR Nats in the parts area. A lot of people have them laying around in their for sale parts. Most of the ones I bough over the years were from vendors at shows.
 
Thanks Geof that would be great , just let me know what you find please.

As for eBay... I searched and found two gears and neither were what I needed.

As for a chart.... I have my yearone speedo gear chart but it does not cover my tire size or my ring and pinion ratio.

The highest gear yearone sells I believe is a 43 tooth (blue I think) and that's for a 215/60/15 with 4.10s........ I need 275/60/15 for 4.56

Thanks guys
 
DusterDude72 said:
As for a chart.... I have my yearone speedo gear chart but it does not cover my tire size or my ring and pinion ratio.
Click to expand...

That is why I suggested getting access to a MOPAR Performance Chassis Book. If it doesn't have your exact tire size and ratio, it will at least get you close enough to figure out which speedo gear you need before you waste time and money on one that's not correct.
 
I'm taking my camera to the Nats too, and I'll snap a picture of this guys chart and post it too. I've seen him in the same spot for many years now and has trans stuff galore as well as the speedo gears. For all who are going, his spot is right inside the rear gate to the right if you come in off Refugee Rd. Geof
 
where is it located at Geof? how far from Jackson?

If I can't make it ...any pics and info you could snag would be greatly appreciated.

Thanks buddy!
 
The Nats are in Columbus, Oh., about 3 hours from Jackson. Not exactly around the corner, but not that far either. I am just going down on saturday to drop off some purchased items for FABO members, and take some core items to turn in for $$$. If you'd like to ride down just for the day, I have 1 extra spot in my truck for a rider. You would need to be in Pinckney at 4:00 a.m. and plan on being back at around 11:00 p.m. It's a lot to see in one day, but if you needed to look for items for your Duster, you won't find a better selection nearby. Just be prepared for the typical Nats markup!!! OUCH!!! Let me know if you'd like to tag along and we'll work out some details, Geof
 
DusterDude72 said:
Ok everyone, back when I bought my duster...just before I got it the kid had the 489 8 3/4 rear rebuilt and SAID it had 4.10 gears in it.

well....

I need a speedo gear because i don't have one so I figured for the heck of it I would check to make sure it was 4.10 gears.

NOW...I think I calculated this right...so i will run it passed everyone for there input.

I put a peice of tape on the drive shaft and a peice of tape on the tires.....the drive shaft turned roughly 4.5 times to 1 tire revolution......x that by 10 and I get 45 drive shaft revolutions to 10 tire revolutions.

now I am sure since I was not using my (precision masking tape) that I could be off by .6 on my revolution .....which would give me 45.6 ....devide that by 10 would give me 4.56.

so am I right in how I came up with this? and would you all agree that 4.56's is the gear I have with the number of rotations I came up with?

and also ....who sells speedo gears in the 4.56 range for my 904 in my duster?

year one stops at 4.10's and summit does not seem to have them either.

Thanks in advance everyone!
Click to expand...

If you can't get a gear new try looking in 70's model RV's at the junkyard, many came with 4.56's/4.88's, most of the 42-43 tooth gears I have came out of those, I found a class A with an industrial 440 and 5.13's but it had a speed reducing box inline on the cable so that probably wouldn't work on yours.
 
Joe, I'm assuming you have sg.? If it's "open", you'll need to lock one wheel and take turns on drive shaft x 2. Good Luck, ateam.
 
Ateam, are you refering to me or Joe?

if you are refering to me, I already a little over a weeke ago jacked the car up and spun the tires and came to a conclusion as to what gear I have.

I was "TOLD" I have a sure grip....but I can't honestly say exactly what I have.

I know when I turn one wheel...the other wheel turns the same direction as the one I am turning and with no slop/play.

I know before I bought the car that the previous owner had just had are local performance drive train shop go through the hole rear end and rebuild it....and I know it has 4.56 gearing but as to if there as any other goodies in there, I do not know
 
Well, I have bad news to report from the Mopar Nationals. The person selling the speedo gears is no longer there, so I was unable to get any information or pictures for the speedo gear seekers. Geof
 
cosgig said:
Well, I have bad news to report from the Mopar Nationals. The person selling the speedo gears is no longer there, so I was unable to get any information or pictures for the speedo gear seekers. Geof
Click to expand...

AWWW bummer, thanks any way Geof ....much appreciated.

I have not got a speedo gear yet, BUT a member her contacted me about a speedo housing,retainer and o-ring for cheap so I got that....so now I just need to pick up a gear....still waiting for year one to reply to my message to them about there prices being miss matched but its been a few days and no reply yet.
 
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