The Stovebolt Site Forums The Shop Area Engine Shop T5 Speedo Gears

Have reached the stage where I need to tweak the T5/Speedo in my 54-3100. Was wondering if any of you who are running the mechanical T5, have figured out how to complete this calibration. The local GM dealership is absolutely NO HELP....don't even show my little adaptor box let alone have a clue about calculating the gear ratio or locating the necessary gear set.

Any suggestions you could offer would be appreciated.

Dave

The folks at www.thegearbox.org really know their stuff. They sent me a Speedo driven gear that put my speedo right on the money.

Thanks for the response. I've checked out their site....they didn't mention the "ratio adaptor" that's on my T5. I'll give them a call in the morning. From what I've figured out, you can add the adaptor if you swap out diffs or tire sizes and use this to correct the variations without going into the transmission to change the drive gear. However, my adaptor (black plastic, with staggered hookups) doesn't have a mfg ID or any other distinguishing mark.

I'll probably wind up having to buy a complete unit to correct the 12% my speedo is off. I was hoping somebody else had the same setup so I could just get a set of gears to make the correction!!!

Sure hate to buy the whole cow when all I want is a glass of milk!!!!! Thanks again,

Dave

You don,t have to change the gear inside the trans. If the speedo is 12% fast pull the driven gear out by removeing the clamp & count the teeth. Get a gear with 1 tooth more or if it,s slow get one with a tooth less. That should get you pretty close. I match the odometer with the mile markers on the freeway to check it but with a GPS system you can do it anywhere.

Ubetcha....I tried 3 vendors....first two gave me the run-around! Kevin from PATC Raptor Transmissions took my info...crunched the numbers, told me to shelf the ratio adaptor and I'll get my new "driven" gear Thursday. It was refreshing!!!

We also chatted about the NWC T5's...they sell the rebuild kits....confirmed that the NWC's use gear oil so I will list his website for all those guys running ATF who will need a rebuild!

http://www.transmissioncenter.net

Thanks for the help guys.

Dave

NOTE: in all fairness: www.thegearbox.org had the correct parts to change out the driven gear...I just asked for the ratio adaptor gears. My mistake!

Dave; glad they fixed you up. Yeah, the driven gear just slips into the housing on the outside of the T5.

There was a big confab on the NWC gear oil/tranny fluid question about a month ago. The conclusion was: not all NWC's use gear oil. I went to the local library, pulled the owners manual for a '89 S-10 p.u. (my T5 decodes to this donor vehicle) and it says right in there to use Dexron II. I think some of the earlier T5's used gear oil.

Sometimes the correct solution to a problem is the simplist solution. I was convinced that the ratio adaptor attached to my T5 held the key to my speedo calibration. I wonder how many guys running T5's are driving off the tach, when all they need to do is scrap the ratio adaptor and pop in the correct single gear????!!!!

As for the NWC's it was pointed out that the bronze synchro units.....which are basically the mechanical speedo boxes, were the candidates for regular gear oil while as you pointed out, the later model electronic speedo units, with the modified synchros were redesigned for the lighter ATF. About 5 months ago there was a huge post with the majority of folks electing to go with the ATF.

I went with the gear oil and my little 1985 mechanical speedo tranny is still smooth as goose-grease. I hope that all the new builders get the correct info on the proper lube.

Dave

I use gear oil in my non-world class in my 58 & ATF in the world class in my Muatang.