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Unread 03-23-2015, 11:29 AM   #1
cgi2099
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1984 CJ7 5-speed Speedometer question

I have an 1984 CJ7 5-speed with a dana 300.

I have 32" wheels/tires with 2.73 gears.

After looking around I think I need a 24 tooth speedometer worm gear, does anyone know where to get one. I can only find them to 26.

Josh

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Unread 03-23-2015, 12:34 PM   #2
walkerhoundvm
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You won't ever find them, they're rarer then hen's teeth. I had one, along with the smaller size housing, but traded it when I made plans to swap gears. The gear swap has stalled, so I am just sticking with my 33-tooth gear I might consider getting a 26-tooth for it to be reasonably accurate, but at present I rarely go over 55 and I have a pretty good feeling for how fast I'm going based on prevailing traffic.

One thing I will say - with that T5, you might just consider swapping gears sooner rather than later. It just might save you having to replace your transmission in a few months. I went through two T5s in a couple of years, and I don't drive like a yahoo - same gearing, smaller tires (31s). That was why I originally planned to swap gears, until my T5 went out again and I just waited on a T176 that I rebuilt. A gear swap is hard for the 2.73s since you'll need a new carrier for the rear, or just swap axles entirely to save time and money.
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Unread 03-23-2015, 12:47 PM   #3
HackFabrication
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There are ratio corrector's that you can purchase which attach at the transfer case and then the speedo cable attaches to them. The gears are easier to source. Here's a pic of one attached to my Dana 20:



I ended up not using it and going with a custom dash with an electronic speedometer that is calibrated off the VSS:

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Unread 03-23-2015, 01:05 PM   #4
cgi2099
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Which gears do you recommend for fuel mileage (going to keep 32-33" tires)? Right now I estimate 17-18 mpg with GPS. Never thought about having issues with the T5, was yours used mainly on-road or off-road?

Quote:
Originally Posted by walkerhoundvm View Post
You won't ever find them, they're rarer then hen's teeth. I had one, along with the smaller size housing, but traded it when I made plans to swap gears. The gear swap has stalled, so I am just sticking with my 33-tooth gear I might consider getting a 26-tooth for it to be reasonably accurate, but at present I rarely go over 55 and I have a pretty good feeling for how fast I'm going based on prevailing traffic.

One thing I will say - with that T5, you might just consider swapping gears sooner rather than later. It just might save you having to replace your transmission in a few months. I went through two T5s in a couple of years, and I don't drive like a yahoo - same gearing, smaller tires (31s). That was why I originally planned to swap gears, until my T5 went out again and I just waited on a T176 that I rebuilt. A gear swap is hard for the 2.73s since you'll need a new carrier for the rear, or just swap axles entirely to save time and money.
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Unread 03-23-2015, 01:05 PM   #5
cgi2099
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Do you knows where I can source one of these adapters?

Quote:
Originally Posted by HackFabrication View Post
There are ratio corrector's that you can purchase which attach at the transfer case and then the speedo cable attaches to them. The gears are easier to source. Here's a pic of one attached to my Dana 20:



I ended up not using it and going with a custom dash with an electronic speedometer that is calibrated off the VSS:

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Unread 03-23-2015, 01:23 PM   #6
walkerhoundvm
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I was using it 99.99% on pavement. Hills, yes, but nothing like stops and starts on a hill or excessive climbing. The second T5 I don't think had more than 20K miles on it. It was the high strain put on it by starting off that finally snapped the shaft. With higher axle gears, that strain is less.

It's a big decision - to swap gears or change axles. It can be a major headache a lot of time and money spent. I can do transmission rebuilds and installs so that was easier for me. An axle swap I could probably do if I found the right axles, but a gear swap is out of my league.

My plan was to jump up to 3.73 with my 31" tires - which would require a change in both front and rear carriers. A 3.54 would only require a rear carrier swap, with new rack and pinion for both obviously. Either 3.73 or 3.54, new axles would be the easiest upgrade. With a T5 either is better than the 2.73s and that would allow you to use 5th gear with more frequency. With a 4spd something more along the lines of 3.31 would be better.

Again, you didn't come here asking for it but that's been my experience with that transmission. Based on others experiences and recommendations, my plan was to gear up.

The alternative is to try to upgrade to a T177 - they have better 1st spd. gearing and are generally better built for handling that sort of axle gearing. You're still stuck trying to find the right speedometer gear
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Unread 03-23-2015, 01:27 PM   #7
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Quote:
Originally Posted by cgi2099 View Post
Do you knows where I can source one of these adapters?
http://www.texasindustrialelectric.com/speedo.asp
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Unread 03-23-2015, 01:39 PM   #8
HackFabrication
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Quote:
Originally Posted by cgi2099 View Post
Which gears do you recommend for fuel mileage (going to keep 32-33" tires)? Right now I estimate 17-18 mpg with GPS. Never thought about having issues with the T5, was yours used mainly on-road or off-road?
IMHO, 4.10 would be a good ratio for 33's and your T5, for overall trail/stree driving performance. You might be able to get by with 3.73 with 32's and 'undersized' 33's.

One of the issues with the T5 is internally, it's not built to handle a lot of torque. The later 'World Class' T5's had different internals to stand up to the healthy Ford 5.0L engines in the Mustangs. Adding large tires with the wrong gearing creates more stress than the transmission was designed for. Get the axle gearing correct for the size tire being used, use sensible driver technique, and with proper maintenance, a T5 will hold up well.

Run some numbers in this calculator: http://www.grimmjeeper.com/gears.html

You'll get a better idea of what your engine is turning at any given speed, and in any given gear.
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Unread 03-23-2015, 01:44 PM   #9
walkerhoundvm
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Quote:
Originally Posted by HackFabrication View Post
Adding large tires with the wrong gearing creates more stress than the transmission was designed for. Get the axle gearing correct for the size tire being used, use sensible driver technique, and with proper maintenance, a T5 will hold up well.
This is absolutely correct - I think in my case the 2.73s with 31" tires, despite driving sensibly, resulted in multiple T5 failures. It's not a bad transmission per se, just needs the right setup.
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Unread 03-23-2015, 01:55 PM   #10
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Quote:
Originally Posted by walkerhoundvm View Post
It's not a bad transmission per se, just needs the right setup.
Exactly. AMC had to create a bunch of gearing setups to help meet CAFE standards. They weren't alone, as all the auto manufacturers had vehicles with woefully high (low numeric) gearing.

If I was ever to (and I'll never) build another CJ, it would be a CJ7 or 8 with either an AOD transmission or a NV4500.
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Unread 03-23-2015, 02:43 PM   #11
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Quote:
Originally Posted by walkerhoundvm View Post
You won't ever find them, they're rarer then hen's teeth. I had one, along with the smaller size housing, but traded it when I made plans to swap gears. The gear swap has stalled, so I am just sticking with my 33-tooth gear I might consider getting a 26-tooth for it to be reasonably accurate, but at present I rarely go over 55 and I have a pretty good feeling for how fast I'm going based on prevailing traffic.

One thing I will say - with that T5, you might just consider swapping gears sooner rather than later. It just might save you having to replace your transmission in a few months. I went through two T5s in a couple of years, and I don't drive like a yahoo - same gearing, smaller tires (31s). That was why I originally planned to swap gears, until my T5 went out again and I just waited on a T176 that I rebuilt. A gear swap is hard for the 2.73s since you'll need a new carrier for the rear, or just swap axles entirely to save time and money.
This.

Also, a 31x10.50 with 2.73's uses a 24, you might even need a 23 (a 24 would be close though).

They can be found, but aren't easy. I have a couple I bought for my 2.73 equipped Jeep. It's dead on with 31's and 2.73's.

Here's a 25. No 24's on ebay right now from my usual search terms.

http://www.ebay.com/itm/MOPAR-SPEEDO...28ec72&vxp=mtr

This guy gets them from time to time. You might check with him, even if he doesn't have one listed.

http://www.ebay.com/itm/MOPAR-SPEEDO...9e1306&vxp=mtr

Don't see any 21-25 housing on there now either. I sold one not too long ago, didn't get much for it.

21-25 will look just like this one, but will ONLY be marked 21-25

http://www.ebay.com/itm/Speedometer-...be9fc9&vxp=mtr
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85 CJ7 258, borla header, Team Rush, MC2100 ,optima batt, Warn 8274, agr super box 2 & pump, T5 w/ B&M shifter, centerforce 2, superior 1 piece axles, warn hubs 2.5 in lift, 31" BFG MT

85 CJ7 258, A/C, T176, MC2100, Team Rush, Warn XD8000i, superwinch hubs, 3in lift 31" BFG AT/KO
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Unread 03-23-2015, 04:27 PM   #12
keith460
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Good God how the prices of speedo gears have jumped up in price. I bought several from the Jeep dealer when they were still around at a cost of $5.00 ea and I thought that was a lot. It's no wonder I hold on to them like gold, I don't know why, but I do.

For good mileage around town and decent highway acceleration, I would not go below 3.73 gears for the T5 and 32" or 33" tires. I have 4.10 gears with 32" tires and the T5 and love it. It's a great combo driving around my area with many hills and winding roads.

And yes, as others have said, a T5 trans with large diameter tires and 2.73 gears will destroy the trans in no time. Too much stress trying to turn the added weight and diameter of large tires without the proper gears. It's the reason the T4 and T5 get such a bad wrap as being a crappy transmission.
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Unread 03-23-2015, 08:56 PM   #13
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Some Dodge Vehicles (and yes... some newer Jeeps) used the same gears as our Dana 300s. Although they may use the short shaft version, you can easily pop the plastic gear off a short shaft and press it on the longer Dana 300 shaft. The plastic part of the long or short shaft version are the same. Tooth count, diameter, even gear color are the same.
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Unread 03-24-2015, 04:14 AM   #14
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Quote:
Originally Posted by Spieg8 View Post
Some Dodge Vehicles (and yes... some newer Jeeps) used the same gears as our Dana 300s. Although they may use the short shaft version, you can easily pop the plastic gear off a short shaft and press it on the longer Dana 300 shaft. The plastic part of the long or short shaft version are the same. Tooth count, diameter, even gear color are the same.
That makes total sense to me and I can believe it. No manufacture will start from scratch just to make a new gear when millions out there already exist. Just changing shafts to accommodate the plastic gears is a common move of auto parts manufactures.

I remember giving my friend a Jeep gear for his Dodge Ram Charger in the 90's and it fit without issues. He needed it to correct his speedo when he installed larger diameter tires.
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