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post #1 of (permalink) Old 06-11-2000, 10:15 PM
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Speedo Gear Replacement

Getting ready to replace the speedo gear in the D300
Wondering if anyone out there has done this before and what are the steps in doing this
I found out that with my 33" tires and the 4.27 axle gears, I need a 35 tooth gear
I see the plate on the case and the cable running into it
What is the procedure

Thanks as always


Chu
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YJ-7
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post #2 of (permalink) Old 06-11-2000, 10:21 PM
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Re: Speedo Gear Replacement

real easy.. yank the plate, out it comes.. if memory serves, they are steel on dana 300's, and nylon on quadra-track...

~~Elusive~~
it's sort of still a cj thingy....see it at http://www.jeepgod.net
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post #3 of (permalink) Old 06-11-2000, 11:21 PM
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Re: Speedo Gear Replacement

Like Elusive said:
Remove the plate where the cable enters the D300. I used some channel locks to pull out the gear. Swap gears and re-install the plate and cable. Be sure the new gear is seated properly. I ended up doing it twice because the teeth didn't engage properly.

Tom

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post #4 of (permalink) Old 06-12-2000, 06:17 AM
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Re: Speedo Gear Replacement

Chu,
I just replaced mine two weeks ago. Like elusive and Tom said it is very simple to replace. Mine had 4.10 gears stock. 33's gave me a 15% increase in speedo reading. I had to go to fewer teeth--31 teeth down to 27. I'm not sure what your readings were before but if your speedo was reading higher than actual speed you need fewer teeth to adust the gearing. I'm sure you rechecked your math and I didn't change R&P gearing on mine so I probably am throwing up a flag for nothing. It's an easy job in just a few minutes. When you hit your regular routes to and from the store or work, it's surprising what speed you really are going when you thought you were just staying with the traffic before. I was always 5 miles over just staying with the flow!![img]/wwwthreads_images/icons/tongue.gif[/img]


Brit [img]/wwwthreads_images/icons/laugh.gif[/img]
85 CJ7 [img]/wwwthreads_images/icons/tongue.gif[/img][img]/wwwthreads_images/icons/smile.gif[/img]
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post #5 of (permalink) Old 06-12-2000, 04:29 PM
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Re: Speedo Gear Replacement

Big flag time
Could you check my math for me then please?

I had a 2.73 gears now are 4.27
Had 28" tires now have 33s
Dana 300 transfer case

the factory speedo gear is a 27
I come up with a 36 tooth


Chu
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post #6 of (permalink) Old 06-12-2000, 08:04 PM
 
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Re: Speedo Gear Replacement

Where did you all go to get the new gear?

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post #7 of (permalink) Old 06-12-2000, 08:14 PM
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Re: Speedo Gear Replacement

Just called the local Jeep dealer
Bought a 36 tooth nylon speedo gear for the Dana 300
Cost?
$7.80

Chu
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post #8 of (permalink) Old 06-12-2000, 08:35 PM
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Re: Speedo Gear Replacement

Jeez, can you guys help a "stranger" who last had a math class in 1970 with this stuff? I have a STOCK 95 Wrangler with 31" BFG's and a 4 banger. CJDAVE was kind enough to answer a post on this a while back, but I had no idea how to figure out his formula which used revolutions per mile. Like I said, everything in this used YJ is stock except for the tires.
Thanks ahead of time!

post #9 of (permalink) Old 06-12-2000, 08:42 PM
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Re: Speedo Gear Replacement

this site will tell ya

http://www.jeeptech.com/java/Speedo.html



Chu
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post #10 of (permalink) Old 06-12-2000, 09:43 PM
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Re: Speedo Gear Replacement

Chu,
I think you got it right or at least close[img]/wwwthreads_images/icons/smile.gif[/img]. Remember, I didn't change my gearing at the differential. (# of teeth old speedo gear) X (new gear ratio) divide by (old gear ratio)=# of teeth on new speedo gear.

(27) X (4.27) / (2.73)= 42.23 That is assuming you kept tires the same.

It would be more accurate if you measured the tire diameter of old and new tires
since you changed tire sizes. If you went from an actual 28" to 33" (33)/(28)=1.1786 or a 17.86% increase in tire size. Then you need to reduce the above calculation by the same % as your tire increase. I just used the numbers you gave as an example. To figure a decrease in % you multiply by(1- % change)
1 - .1786= 0.8214

(42.23) X (0.8214)=(34.68.) teeth on new speedo gear. Good work!!![img]/wwwthreads_images/icons/wink.gif[/img]Substitue your numbers in and you'll probably be pretty close.

I didn't know my original tire diameter since I bought the CJ with 31's. I put 33's on last fall and I knew I was going faster than the speedometer was reading. I clocked about 10 or 12 miles using highway signs for distance. They vary considerably, so I just used several miles of road holding steady at 52mph to go one mile in each minute--or 60mph actual speed .
That ratio was: old gear X apparentspeed/ actual speed= new gear
or 31 teeth X 52mph/ 60mph = 26.87 or 27 teeth on the new gear.

Chu, you could check your self by finding the speedometer reading for one accurately measured mile or average several like I did. Then you could get a more accurate estimate if you don't have your old tires to measure. You also can have someone ride alongside who has a known accurate speedometer and check your speed when they are going evenly alongside. You need to know their speed and yours to be fairly close to accurate.
I'll bet I made that really more painful than it needs to be and no one should ever ask me a math question again [img]/wwwthreads_images/icons/laugh.gif[/img]. Hope it helps but it looks like you figgered pretty close[img]/wwwthreads_images/icons/smile.gif[/img]

Brit [img]/wwwthreads_images/icons/laugh.gif[/img]
85 CJ7 [img]/wwwthreads_images/icons/tongue.gif[/img][img]/wwwthreads_images/icons/smile.gif[/img]
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