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Does anyone have a source for a new speedometer gear for the truck 3 speed transmissions? I'd like to have my speedometer read correctly with the 3.54 rear end ratio I put in it. It had a 4.11 originally. I can get pretty close guessing as I drive, but I'd like to correct it. Any help is appreciated! 

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3 hours ago, Don Coatney said:

You need a speedometer calibration box. Click on the link below.

https://stevemckelvie.wordpress.com/2011/08/01/my-new-speedometerodometer-correction-box/

 

Thanks Don! Once you said that, I remembered I looked into those before, but I didn't want to spend the money. Well, I just ordered an adapter to mount directly off the transmission. It was pricey, but it should fix my issue. I'll report back on hopefully a success story when I get it. Thanks Again!

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9 hours ago, Bobacuda said:

Joe, be sure to post your results.  My speedometer is about 15% too slow.

Will do. Mine is roughly the same. doing the math, I need my speedometer to read 1.1673 times the speed it is reading. 

I found that these people make them to mount directly the the transmission. Clark Brothers Insturments:  http://www.clarkbrothers.net/ratio_adapters.html

I bought the AA11667 part number. It was the closest. http://www.clarkbrothers.net/pdf/SC795_Catalog2_Page_4.pdf

I'll let you know the results once I get my speedometer back from repair and install the adapter. 

 

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My speedometer gear has 16 teeth.  I have scavenged a couple of others and they also have 16 teeth.  I have heard there are also factory 14 & 15 tooth gears, but I have yet to find one and I have no idea what they would do to the speedometer reading. 

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My speedometer is about 25% off after installing a 3.0 rearend in my 52 1/2 ton with a four speed.  I had one of those boxes made for my truck but found that the E brake parts were in the way of me installing it.  I wonder if they make a box that would fit on the back of the speedo instead.

 

1 speedo 1.jpg

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4 hours ago, Reg Evans said:

My speedometer is about 25% off after installing a 3.0 rearend in my 52 1/2 ton with a four speed.  I had one of those boxes made for my truck but found that the E brake parts were in the way of me installing it.  I wonder if they make a box that would fit on the back of the speedo instead.

I hope I don't have this issue on my 3 speed, but going into it I knew it would be a gamble for that same reason. By the looks and dimensions they gave me it should fit. If it doesn't fit I plan on remote mounting it to the frame using a 7/8" transmission end on both sides of a short "jumper"  cable. It won't be "correct" but I'd rather have an accurate speedometer. 

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On 6/23/2017 at 8:27 AM, Bobacuda said:

My speedometer gear has 16 teeth.  I have scavenged a couple of others and they also have 16 teeth.  I have heard there are also factory 14 & 15 tooth gears, but I have yet to find one and I have no idea what they would do to the speedometer reading. 

I have 3:54 third member in the stock rearend housing of my B1B and the speedo is 10 mph slower than actual speed. Not a huge deal but Id like to get it showing the right speed. Ive given a lot of thought to finding the proper speedometer drive gears for this gearing. Im pretty sure that one would have to change the speedometer drive gears as a set, the gear in the housing that threads into the trans and the ring shaped gear that fits over the output shaft of the transmission. Ive been searching for some sort of listing that would show which speedo drive gear set would correspond with the each gearing that was available back then, but as of yet I have not had any luck. My parts book shows a part# but no mention of the differential gear ratios and or different gears for each ratio. Ive been trying to get a in touch with the previous owner who swapped out the third member back in the early 80's to find out what year and model the vehicle was that he got the third member out of both for me a another member here however he has been out of state for a few months In the mean time Im just doing lots of looking to find the answer. With how incredibly cramped the area is where the drive gear is located in the trans I fear a adapter might not fit. I can barely get my hand on the speedometer cable end there.  

                                   John

Edited by John Rogers
There are times when what I type makes no sense :)
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My truck came with 4:11 gears, 3 on the tree with Fluid Drive and 16" wheels - 16 tooth speedometer gear.  Somewhere, I have another such gear from a 1951 non-Fluid Drive truck (I assume it had 16" tires), 16 tooth gear.  I also have a 16 tooth speedo gear from a 1948 Dodge Coupe with Fluid Drive and 15" tires - 16 tooth speedometer gear.

I am now learning to use the MPH app on my phone...

 

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13 minutes ago, Bobacuda said:

My truck came with 4:11 gears, 3 on the tree with Fluid Drive and 16" wheels - 16 tooth speedometer gear.  Somewhere, I have another such gear from a 1951 non-Fluid Drive truck (I assume it had 16" tires), 16 tooth gear.  I also have a 16 tooth speedo gear from a 1948 Dodge Coupe with Fluid Drive and 15" tires - 16 tooth speedometer gear.

I am now learning to use the MPH app on my phone...

 

Fluid drive makes no difference. The speedometer is based on driveshaft revolutions per mile. Both differential gearing and tire diameter will affect driveshaft turns per mile.

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I received the speedometer ratio adapter this evening (it came faster than I thought)! It came in a large box which got me nervous, but luckily it was in a smaller box within! 

I tore the boxes open, and was still a little nervous about it fitting, but I put the appropriate drive cable adapters on (seen in the pictures) and it fits very well on the truck. I'm very happy with is so far, but I have yet to test it until I get the speedometer back from being repaired. Hopefully the speedometer will come back this week, and I'll have another report. Pictures are below!  Warning, some of the pictures are turned! 

1.jpg

2.jpg

3.jpg

4.jpg

 

6.jpg

7.jpg

Edited by 52b3b Joe
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2 hours ago, JBNeal said:

ya know the underside of your truck is obscenely spotless...I'm totes j :cool:

Lol, it took a lot of time to get it that clean, but don't worry, it's getting plenty of road grime and grease on it already. It's getting broke-in. ;)

1 hour ago, Merle Coggins said:

I don't think I have that much room with my 4 speed trans. 

Does the ratio stay the same in straight through mode?

Yes it stays the same. It has a counter-shaft in the center to keep the same ratio either way.

 

55 minutes ago, Reg Evans said:

Yeah, one of those wouldn't fit on my 4 speed either like I said in post #8

I don't see why you couldn't remote mount the adapter on the frame and have a short cable to connect it to the transmission. If it didn't fit on mine, I planned on mounting it somewhere on the frame. If you google "speedometer cable extension" you can find them for sale for $20 or so. The transmission end is a 7/8-16 thread. 

8.jpg

Edited by 52b3b Joe
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31 minutes ago, The Oil Soup said:

Could it mount directly behind the speedo?

You would have to make some sort of cable adapters to make it work. The speedometer head has a smaller 5/8"-18 thread, so you'd have to somehow adapt to the 7/8"--16 thread of the adapter. I suppose someone might make an adapter for the 5/8-16 cables, but I'm not sure.

I might be a little concerned with the drag of the adapter on the cable as it turns over that length of cable if mounting it at the speedometer. Having it driven directly off the transmission (or as close as possible) would remove any chance of added load to the cable. I don't think a speedometer cable will take a whole lot of extra load before failing, but I really don't know or have any experience with this. When I spun the adapter before it was installed, it was a little stiff but I'm guessing it will loosen up over time as the fresh grease moves around a little. Once I drive it some, I'll take it off and let you know if that is the case.

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My repaired speedometer came in the mail today, so I put it in after work and took it for a drive. I finally have a usable speedometer in my truck! It's pretty nice knowing how fast I'm going without worrying or without a speedometer app on my phone. I drove about 20 miles, and it is pretty enjoyable! According to the speedometer app on my phone, my speedometer is reading 57-58 when my phone is reading 55. Up to 40 mph, they are both reading the same, but the truck speedometer seems to have some error over 40. I can live with the 2-3 off at 55 mph though! 

As a side note, with the speedometer issues I had, I could never get a good feel for the performance of the truck. Now that I can see the acceleration, it definitely has more pep than I thought! I guess I don't have anything to compare it to though....

Here is a video (it's not the smartest thing to take a video when driving so the video quality isn't the best):

 

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8 minutes ago, Merle Coggins said:

What rear gears do you have? I don't think mine accelerates that well.

It has 3.54 gears. It really surprised me, but I checked it against my phone and its reading right. My dad always comments about how quick it accelerates and how fun it is to drive. I have a Chrysler Industrial 230 in it. Its bored .030 over and I have no idea what the compression ratio is. I've never had a reason to check the compression. 

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