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  #16 (permalink)  
Old 07-05-2006, 10:20 PM
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Quote:
Originally Posted by oldguy829
Crosly, took this rookie a minute to figure out BOP.
I went to the chart for GM gears. They didn't differentiate between Chevy and Buick/Olds/Pont. anyway, the 18 tooth Green matched what came out, and fit properly. Does that mean it is not a chevy trans?
BOP= buick , olds, pontiac , cadillac...

Chevy & BOP speed-O parts will swap around , whcih cuase problems for a DIY person.

tail housings are different from a BOP to a chevy... chevy has a small diameter speed-O bullet housing with a smaller plastic driven gear.

BOP has a large diameter bullet & larger diameter driven gears. they start in the mid 30's tooth count

The gears on the output shaft are smaller diameter for a BOP tail housing. A good BOP drive gear will work in a chevy setup for a short time , then it starts to skip.

The plastic gears for the output shaft look near the same diameter , the same clip will hold them on ( some BOP used a wider clip design) , the difference is about .080 in diameter I-I-R-Correctly . Depending on the wear in each related part , the speed-o meter starts jumping when the gears do not mesh correctly.

photo shows a BOP 6 inch tail housing on the right.... a chevy 9 inch tail housing in the middle... 12 inch t-350 tail housing on the left with a BOP speed-O hole.





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  #17 (permalink)  
Old 07-05-2006, 10:52 PM
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[QUOTE=oldguy829]

Back to calculating the rear end ratio guys. If I jack up one wheel and spin it, is it one rev or two, to count the pinion revs?

QUOTE]

It's two turns of the back tire if one of them is on the ground motionless. If you do one turn, you'll get a number that's half your true ratio, and it will likely make no sense. They never made a 1.54 ratio, at least not to my knowledge.

If you jack up both tires, the one you can't see will move while you're not looking at it, and the whole shabizzle will be thrown off.
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Old 07-06-2006, 03:08 PM
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[QUOTE=xntrik]What makes you think that his speedo is closer than plus or minus 2-3 mph?
Why go buy the wrong gears?
Radar or GPS is the only accurate way.


I guess I wasn,t clear enough that is one tooth for each 2 1/2 mph you want to change the speedometer If at 60 your spedo is at 72 you would add 5 teeth to slow it down to read 60 on the speedo.So you add teeth to slow it down and subtract teeth to speed it up.I paid 5 dolors for the gears at the wrecking yard. Sorry I wasn't clear enough with my instructions
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Old 07-08-2006, 01:17 PM
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[QUOTE=DOUBLEDICK]
Quote:
Originally Posted by xntrik
What makes you think that his speedo is closer than plus or minus 2-3 mph?
Why go buy the wrong gears?
Radar or GPS is the only accurate way.


I guess I wasn,t clear enough that is one tooth for each 2 1/2 mph you want to change the speedometer If at 60 your spedo is at 72 you would add 5 teeth to slow it down to read 60 on the speedo.So you add teeth to slow it down and subtract teeth to speed it up.I paid 5 dolors for the gears at the wrecking yard. Sorry I wasn't clear enough with my instructions

I apologize that I wasn't clear. What I meant was that when you are checking speed against someone elses vehicle, how do you know how accurate the other car's speedometer is. If it is 3 off and you go buy a gear, then you are 3 off too,,,,,, all you have done is waste time and money.

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Last edited by xntrik; 07-08-2006 at 02:39 PM.
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Old 07-09-2006, 07:47 AM
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xntrx you seem to be just looking for an argument so you should save the 5 bucks and take yours to a speedo shop any pay 120$ so you dont have to take a chance on trying.
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Old 07-09-2006, 09:28 AM
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Quote:
Originally Posted by DOUBLEDICK
xntrx you seem to be just looking for an argument so you should save the 5 bucks and take yours to a speedo shop any pay 120$ so you dont have to take a chance on trying.

Cops will radar check you for free. Friends have a GPS. Gears are still $5.

Grandpa always said, "Never argue with an idiot, someone listening might not be able to tell the difference."

Last edited by xntrik; 07-09-2006 at 09:35 AM.
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Old 07-09-2006, 07:03 PM
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IF the posts continue down hill towards personal attacks ...... I will correct the situation.

please stick to the speed-O correction topic.


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Old 07-11-2006, 09:17 PM
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Speedo way off

Thanks Guys. This is why I love this site. Ask a simple question, and get taken to school. don't remember who advised what, but I learned this.
A. speedometers wear out. they spin, but not accurately. Local shop checked it out, off by over 5 MPH. reworked it, new magnets I think, and it is good to go, for $75.00. Now I can check it against radar/etc. and put the right gears in. B. the TH350 isn't just Chevy (duh), Got a buddy at a shop who is going to figure out what it is for me. C. speedo gears interchange, but that doesn't make them right. (I may end up needing to swap out the tail piece to get the right bullet in the right place to do the job right.)
Taking the wife on a little vacation, so the solution will have to wait a while.
But now i know what to do, how to do it, and what to look for.
Thanks again.
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Old 07-11-2006, 09:36 PM
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good to read you found a speed-O shop that could work on the old stuff.

have a good vacation.

I just returned this eve from mine in Ohio & Indiana.







Quote:
Originally Posted by oldguy829
Thanks Guys. This is why I love this site. Ask a simple question, and get taken to school. don't remember who advised what, but I learned this.
A. speedometers wear out. they spin, but not accurately. Local shop checked it out, off by over 5 MPH. reworked it, new magnets I think, and it is good to go, for $75.00. Now I can check it against radar/etc. and put the right gears in. B. the TH350 isn't just Chevy (duh), Got a buddy at a shop who is going to figure out what it is for me. C. speedo gears interchange, but that doesn't make them right. (I may end up needing to swap out the tail piece to get the right bullet in the right place to do the job right.)
Taking the wife on a little vacation, so the solution will have to wait a while.
But now i know what to do, how to do it, and what to look for.
Thanks again.
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Old 07-11-2006, 10:02 PM
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What's the name of the shop you used? I have speedo head problems on my Suburban, and there's not a speedo shop around here any more, but I get down to S.A. a couple of times a year, so maybe they could fix mine.
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Old 07-22-2006, 08:10 PM
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speedo gears way off

I used SX Callaghan, 824 S. Laredo St. that's the south edge of downtown. just east of IH 10, near Durango. Nice people, they said were jammed up, so it took 3 days. LOL.
Just got back in town, so, no results yet. I'll post again when I get it in and test it.
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Old 07-23-2006, 05:44 PM
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I put on new tires and had my car RADAR checked yesterday. Now it is 2 mph faster than the speedo reads @ 55.
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Old 08-11-2006, 04:16 PM
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Speedo way off

All is well. The speedo rebuild picked up 10 percent and a gear swap did the rest. To the one who questioned my 18 tooth green gear. We were both right. The one that came out was 18 tooth green (BOP) , ( but the speedo didn't work at all .) what it needed was a chevy 9 tooth green (which I later changed to a 10 tooth brown for the final adjustment). Nice to fix something and have it work perfectly. Couldn't have done it without the help. Thanks again.
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