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turbo 400 speedometer gears ? (where and what to buy)

  
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turbo 400 speedometer gears ? (where and what to buy)

 
buzzinhalfdoz buzzinhalfdoz
User | Posts: 233 | Joined: 07/12
Posted: 05/18/13
08:20 AM

need help correcting my speedo. it is way off now 20-30mph.
i know i will need to replace both gears(drive and driven).
i cant figure out how to determin what set up to order?
i have 3.15 gears and 26" tall tires.(stock 73 trans)
help???
thanks for all the past help, my friends love the way this 455 sleeper runs...  

barneyformula barneyformula
Addict | Posts: 3298 | Joined: 01/07
Posted: 05/18/13
12:02 PM

Good luck finding drive gears! The driven gears are no problem but all the new drive gears are steel-presson gears that didn't fit my TH400. I had a 16 tooth drive and needed a 15 tooth to calibrate my Tempest and I went around to a couple of trans shops and asked until I found a used one. You may need to change the adapter that goes in the side of the tail housing of the trans as well, they are mark with a minimum and maximum tooth count that they will fit. Wallace racing has a good calculator on their website for choosing the right combo of gears.
Steve  
A little help... 'cause we don't all have to learn the hard way!

buzzinhalfdoz buzzinhalfdoz
User | Posts: 233 | Joined: 07/12
Posted: 05/18/13
12:07 PM

thanks i will give wallace a look.  

ROWSLEY ROWSLEY
Guru | Posts: 981 | Joined: 07/11
Posted: 05/19/13
10:29 PM

it would help to know what you have now for speedo gears. speedo slow or fast?  
76 455/4spd TRANS AM
69 GRAND PRIX 455/5SPD

70bird 70bird
Guru | Posts: 1064 | Joined: 02/13
Posted: 05/20/13
03:12 AM

Hello

If the gears you need are difficult to find do they make the "inline" speedo "correctors" that Ford used on their 391 and 411 geared cars from the factory?  

buzzinhalfdoz buzzinhalfdoz
User | Posts: 233 | Joined: 07/12
Posted: 05/22/13
05:35 AM

speedo is now fast, driving aprox 40mph shows aprox60-70mph on speedo.
trannie came out of a 73 bonnie, with airplane gears i am sure.
i now have 3.15 gears and 26" tall tires.  

barneyformula barneyformula
Addict | Posts: 3298 | Joined: 01/07
Posted: 05/22/13
09:07 AM

First things first, you need to know what drive gear is on the tailshaft of the trans. You don't necessarily need to pull the driveshaft and tailhousing to check, just remove the speedo-cable and the driven gear adapter so you can see inside. Clean the drive gear off with brakekleen and mark one tooth with a sharpie marker, turn the driveshaft and count the teeth. Now you can plug the numbers into the Wallace Racing calculator and it will tell you what driven gear you need. While the adapter housing is out, clean it off and see what tooth range is cast into it and count the teeth on the driven gear as well.
Steve  
A little help... 'cause we don't all have to learn the hard way!

mb68bird mb68bird
Enthusiast | Posts: 468 | Joined: 06/10
Posted: 05/22/13
01:27 PM

Any local transmission shop that has been in buisness a while should have some spedo gears laying around.  

buzzinhalfdoz buzzinhalfdoz
User | Posts: 233 | Joined: 07/12
Posted: 05/22/13
01:33 PM

their is a local tranny shop not 4 miles from home, been their a long time.
i know one of the guys that works their.
after i c what i need i will give him a try.
thanks for the idea.  

smruppik smruppik
New User | Posts: 1 | Joined: 03/14
Posted: 03/18/14
07:46 AM

Hi guys i`m chasing a 16 tooth drive gear for a TH400, have any of you got one or do you know where i could get one? Cheers Steve.  

big-g-67gto big-g-67gto
Guru | Posts: 905 | Joined: 07/10
Posted: 03/18/14
02:42 PM

there is a company on the web that will make you a custom adapter that will fix your speedo, pronto.....had one made for my 74 grand am, about $80, done, just screw it to the tranny and hook up the cable....let me research it and get back to you all.  (key word ratio adapter)

Grin  
I got that Tin Indian GRIN!!

big-g-67gto big-g-67gto
Guru | Posts: 905 | Joined: 07/10
Posted: 03/18/14
07:26 PM

I realize this is and old post, but from an fyi aspect, rather than search high and low for different speedo gears to correct your speedometer,make your life a little easier with a ratio adapter. I went threw PATC Transmissions, 888 201 2066, they will have you check the ground speed of your car with a GPS vs the reading on your speedometer at three different speeds. You relay the info to them and they build you an adapter to match the % of error at the gauge. It takes minutes to install when you get it and the accuracy of mine was spot on.

Grin  
I got that Tin Indian GRIN!!

ROWSLEY ROWSLEY
Guru | Posts: 981 | Joined: 07/11
Posted: 03/18/14
11:07 PM

welcome steve. you should have started a new thread.

any trans shop should be able to get you a gear. or try trans star they sell all kinds of tranny parts! what about ebay?  
76 455/4spd TRANS AM
69 GRAND PRIX 455/5SPD

gtojack1366 gtojack1366
Guru | Posts: 1223 | Joined: 11/09
Posted: 03/19/14
03:04 PM

Here's a 16 tooth 400 drive gear for sale .   http://www.ebay.com/itm/GM-TURBO-400-TRANSMISSION-OEM-16-TOOTH-STEEL-SPEEDO-GEAR-/251473984065?_trksid=p2054897.l4276