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Regeared With 3.73's, New Question

itsmeagain5789

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itsmeagain5789 Enthusiast

itsmeagain5789

Posted
Posted

so i went out to the junk yard and got a pretty decent deal on a whole axle that has 3.73 gears in it. the Truck packs a punch now! however, my only disappointment on this is how off the mileage is. driving down the road at 39mph according to GPS, the speedo says 45. I don't mind so much that its off, but what i don't like is that the odometer is going to be marking this significant difference. Since my truck has low mileage, I kind of wanted to keep it that way. Will bigger tires help, or is this something in the transmission? Can I do anything to fix this, or atleast make it better?

brims Senior Enthusiast

brims

Posted
Posted

I could be wrong, but I think your truck may have a mechanical speedo. If so, in the tail housing of the transmission there are some gears. 1 you can replace easily, 1 you have to remove the drive shaft and tail housing I believe.

 

Here's a site that tells more about it. http://www.tciauto.com/Products/TechInfo/speedo_gears.asp Not sure when they went to an electronic speedo. If I'm wrong, you can get a tune or a Diablo Sport Predator or similar handheld. Someone should chime in soon as to which way to go.

 

EDIT: Ok, looks like it's electronic. Get a tune or a handheld.

superjim Senior Enthusiast

superjim

Posted
Posted

You could get a tune...a handheld. or you could take it by the dealer..or anyplace that has a TECH 2, and they can readjust the speedometer in about 5 minutes.

Stevens03 Senior Enthusiast

Stevens03

Posted
Posted

To answer your question, Yes you can do something about it. A good transmission shop should be able to fix you up. :thumbs:

brims Senior Enthusiast

brims

Posted
Posted
You could get a tune...a handheld. or you could take it by the dealer..or anyplace that has a TECH 2, and they can readjust the speedometer in about 5 minutes.

 

If you take it to the dealer, it may depend on the dealer itself, I've heard some won't even correct for different size tires, even if they are optional from the factory.

superjim Senior Enthusiast

superjim

Posted
Posted
Great, that is exactly what i was hoping for. btw, what is a handheld or Tech 2?

 

 

A "HANDHELD" is a device, like a Diablo Predator, that plugs into the OBD port on your truck and allows you to make changes to the computer.

 

Some people use them to do custom tunes to their truck.

 

A "TECH 2" is a device that usually only dealers have that does the same thing.

 

Like STEVENS07 said, a good trans shop should be able to do that also...and may be cheaper and a lot less hassle than the dealer.

rodram Enthusiast

rodram

Posted
Posted
so i went out to the junk yard and got a pretty decent deal on a whole axle that has 3.73 gears in it. the Truck packs a punch now! however, my only disappointment on this is how off the mileage is. driving down the road at 39mph according to GPS, the speedo says 45. I don't mind so much that its off, but what i don't like is that the odometer is going to be marking this significant difference. Since my truck has low mileage, I kind of wanted to keep it that way. Will bigger tires help, or is this something in the transmission? Can I do anything to fix this, or atleast make it better?

 

Bigger tires (ie., larger diameter) would just take away from the extra zip you just got from your 'new' 3.73 axle. Looks like your speedo and odometer will be about 15% off, so for every 10,000 miles you drive, your odometer will show 11,500 miles. Easiest way to adjust is to re-program your computer with a handheld programmer ... one available product seen around our parts is the Hypertech Power Programmer ... google them to find out more about what these can do... and there are a number of other brands out there too.

 

Previous owner of my truck must have re-programmed mine for the slightly larger tires he had on the truck... I went back to stock size/grade of tire and now my speedo is out about 5 or 6% according to my GPS.

66nova Senior Enthusiast

66nova

Posted
Posted

Are we talking about his 93 here? That is an OBD1 system. What Tuner or Hand Held is going to adjust it?

rodram Enthusiast

rodram

Posted
Posted

ODB1 ...? OOps!.. I retract my last post and apologize... I do not know what programmer can adjust or calibrate the computer on an ODB1 ... :crackup:

itsmeagain5789 Enthusiast

itsmeagain5789

Posted
  • Author
Posted

Yes, sorry I didn't mention that I had an obd1 system. I called a speedometer shop and they charge like $300 for it :rolleyes: . So I am trying to find another way. They did mention that they can install an adapter, program the computer, and there was one other way that I didn't really pay attention too because the $300 price tag was still sinking in.. i don't think i'm willing to pay that much. Any other ideas?

rodram Enthusiast

rodram

Posted
Posted

can you find out what part the trans shop would plan to replace....

find one at a junk yard or parts shop...

and then replace it yourself..

you sound like someone who likes to do the work yourself to save the labour costs.

(and I don't blame you for that)

 

Also, from looking at the net today, it looks like obd1 custom tunes cost in the order of $250-$300 just for the eprom... but maybe for those $$$ you can get a little extra performance as well as get your speedo calibrated.

itsmeagain5789 Enthusiast

itsmeagain5789

Posted
  • Author
Posted
can you find out what part the trans shop would plan to replace....

find one at a junk yard or parts shop...

and then replace it yourself..

you sound like someone who likes to do the work yourself to save the labour costs.

(and I don't blame you for that)

 

Also, from looking at the net today, it looks like obd1 custom tunes cost in the order of $250-$300 just for the eprom... but maybe for those $$ you can get a little extra performance as well as get your speedo calibrated.

yea, I love working on my trucks, and doing whatever i can do to save some money. But dang, i didnt know the programmers were that expensive for these old trucks. i wish there was just a gear in the transmission i could just replace. if i dont find any other cheaper alternative i might just have to live with it. I don't put too many miles on this truck either way. i mainly use it for towing and working, but I am going to do a full resto on it down the road (it has sentimental value), so that is why I was trying to preserve the mileage on it.

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