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I know I have seen the explanation as to checking and correcting the accuracy of your speedometer. With the new T-5 transmission, I just want to be sure I'm on the money. My T-5 has a mechanical speedometer hook up and at this point I have hooked my speedometer cable to the T-5. According to the speedometer, I seem to going faster than I really am, which may not be all that bad but, can someone give me the info on checking the speedometer and just what to do to get it accurate.

Thanks!

Joe

Just check what the odometer reads between mile markers. This will tell you what percentage off the drive gear is and you can install a new drive gear that is close to that percentage from the one presently in the transmission.

Here is what I did using the street, an rpm gauge and an rpm calculator....

First make sure the odometer is right on the mile and get an odometer gear adapter that goes on the outside of the xmission speedo cable outlet, if necessary.
Then rotate the arm inside the speedo gauge where the needle coil-spring attaches until the speed matches a given rpm.
Use a rpm calculator online.
This can be tricky and take several tries as the very slightest rotation has quiet an effect on the reading.

I set the sweetspot to be accurate around 40-70 mph, as the speedo needle is not 100% across it's entire range.

If you don't want to putz around, just bring it to a speedo adjustment shop.

6cyl,
Do you know where you got the speed cable, and which vehicle it came from? I pulled one of an S10, and the tranny end had the correct fitting but the speedo end used a collar/retainer instead of screwing directly onto the speedometer.

tlorber -

Believe it or not, it's the one that was on the truck. It was pretty long and loose so I tugged on it a little bit and it stretched far enough to reach the T-5. I looked at the plastic gear in the T-5 and the end of the cable and they looked the same so I screwed it on. It works fine and it may be accurate. I've just got to find a stretch of the interstate with some mile markers and check it out.

My guess would be that you could buy a new one for not a whole lot of money at a NAPPA or good auto parts store. I wouldn't think they would be real expensive, but I might be wrong.

Wish I could be more help! Good luck!

Joe

Joe it should take you one min. to go 1 mile at 60mph. I think I 30 has the mile markers.
Tom

just have someone ride next to you on a lonely highway and they can shout the speed at which they are traveling, then compare that to your speedometer.

Then, if you are industrious, you can take a pic of your speedo assembly, put it in photoshop and change the numbers to match the new data. Print it out then glue it over the existing numbers.

This is a constant problem for car buffs though. What needs to be invented is an unit that plugs in between the speedo cable and the speedo that has a variable adjustment mechanism which corrects for errors. Then you wouldn't have to play the guessing game every time you change the drivetrain variables.

Tab,

That's called a GPS.

Joe, I got a new cable kit at Auto Zone for about, or less than, 10 bucks. Most do not have the housing with cable already in it. My kit has a new cable that you cut to length. Instructions included.

Try this page for good information,
http://www.speedometershop.com/rep-pag.htm

Joe

The T5 transmission has a factory installed offset adaptor that screws into the transmission and the cable screws into that. If you put your cable directly into the tranny your speedo will be way-off. (high)

A company in Milwaukee "Speedo solutions" (414)
463-6660 might be able to help you get the correct gear sets to calibrate your speedo. Have your OD ratio number, and tire/wheel diameter and ring/pinion ratio available. The local Chevy dealership doesn't even have a picture of the T5 adaptor so if you didn't get one you might have to go back to a j-yard and do some looking. I have a picture of the adaptor on page 10 of my webshots "shoebox. Hope this helps.

This is the first I have heard of an adapter. I know you might need something like that on an electric speedometer set up on a T-5, but not on a regular set up. Why would they use that when they could have put the correct gear in the back of the transmission? I guess I don't understand. :confused:

Joe

Mine had one on it. If i plug straight into the tranny my speedo shows way higher than I'm actually travelling. If I use the adapter it reads a little lower than I'm going.

Or use your cell phones.

G.M. used these adapters on practically all there trucks with manual trans. They fine tune the speedo with these. I keep a bunch of them around & check the odometer with the freeway mile markers. I find one that is close to the amount of change needed. If it is the opposite of what I want I take the gears out & switch them. You can pick them up at the pull it yourself lots. The checkout guys don,t know what they are & don,t hardly charge much for them.

Any idea if there is a reference for these things anywhere? It would be nice if we could find some GM part numbers for various adapters and their ratios...maybe we could change this from a "stick one on and try it" deal to a "look up the right one on the chart and install it" deal.

As I mentioned earlier....they don't even show up on the GM dealers parts screens. No numbers....no charts.....but once again, "Speedo Solutions" (414) 463-6660 may be helpful in getting it right the FIRST time. Be sure to have your OD ratio, R&P ratio, and tire diameter available.

Both of the t-5 transmissions i bought have the gear reduction box.One is rectangle and the other is a oblong round shape.I need to check the speedometer and look into getting the right gear for the reduction box.It would be helpful if we all could list our trucks specs and what gear we used in the reduction box.I like texmos idea !!!!

The one that came on my T-5 has a GM logo on it and has the following numbers: 663AJ6 and then under that is .7333AAC

I am running a 230 with a T-5 behind it that has a .72 overdrive and a 3.73 rear end. With this thing installed my speedo reads about 10 mph slow at 65 mph (checked against a GPS).

Had an oportunity to get out on Interstate 20 today and readily found mile markers to check my speed-distance. I made it between the mile markers with 1.2 miles rolling up on the odometer. I guess that translates to meaning that my speedometer is runing about 20% fast. While checking the odometer reading, my speedometer was reading 80 miles per hour. I figure I was actually running about 65 miles per hour, but I'm only guessing.

I'm not really sure what all this means as far as obtaining an adapter, except to report these statistics to an speedometer shop in order to buy an adapter. Is my assumption correct?

Thanks,
Joe

I need some comments I can go with, please?

Thanks,
Joe

Go ten miles for more accuracy. 20% jives with your speed guesstimate. 80/1.2 = 67 mph

You need to slow the speedo down.Count the teeth on the speedo gear at the trans.You will need one with more teeth.One tooth is about equal to two miles per hour.As for the speedo adapters that were spoken about above,they were made by Stewart Warner for GM(and others)to bring the speedo's in the ball park.Hope this helps.

look up united speedometer for the address and phone number. find a place that has mile markers (any Interstate Highway or Sppedometer check point)write down your odometer, miles and tenths drive 5 miles write down odometer reading each mile. call united tell them they will sell you a ratio adaptor that goes between the trans and cable...easier then changing the gear

gtow69 has the right idea and probably the cheapest solution. I just fixed mine the same way. The gear you need is called the "Speedo
driven gear" and is available at The Gear Box.
www.thegearbox.org A 2-tooth change on my gear
changed my reading 10mph.

I was just browsing the archives over the weekend and reading a thread on a "T-5 rebuild manual" which detailed three different "speedometer" gears to be used, depending on the appropriate rear end of the vehicle. See this link for details.

http://www.fordmuscle.com/archives/2002/09/transmissions/LD05-0510-0199.pdf

Dave

Yeah, DW, that's correct. There are 3 different gears (drive gears) that are used. These are on the inside of the tranny. The "driven" gear is the easy one. There are 8 or 10 different gears here. The driven gear and it's housing, is what the speedo cable connects to. Takes 5 min. to change out.