Green89IROC305

Hey All,

Anyone have any place I can find/purchase the white 36 tooth speedo gear?

GM P/N 25513043.

I need the cone shaped gear without the shaft for my VSS. I can only find gears for a cable driven speedometer.

Thanks

jmd

iTrader: (4)

https://transmissioncenter.net/shop/...-speedometers/ Has a 37 tooth.

But there are very few occasions where a 36 is required. Is this for the 3.23 IROC? Stock height tires?

Green89IROC305

Thanks for replying.

This is for my new build - 91 Z28 with 700R4, 3.08 and 245/50/16.

jmd

iTrader: (4)

On a stock third gen with that tire size, GM used a 17 drive, 42 driven speedo gear combination. With different tire sizes, a 41or 43 may be used. Those should be easier to find.

Be prepared for 99% of online speedo gear calculators to give recommendations different than what went into production vehicles.

Green89IROC305

Thank for the information.

The 700R4 transmission that's going into it is out of a different third gen.

I have already confirmed that the drive gear in the transmission is the grey 15 tooth, which is why I am looking for the 36 tooth driven gear after reading the stcky.

Then link you provided has a 37. How far off will that be? I am still holding out that Hawkes can find one though.

I also have the SGI-5E box but I'm not entirely clear on how it can be used to correct a speedometer with the wrong driven gear.

Below is a pic of my drive gear.

jmd

iTrader: (4)

I wondered if you had the 15. Of course, to get the car going, a 37 is the easiest option.

( (36 / 15) - (37 / 15) ) / (36 / 15) gives 2.77% slow.

One setup that could work is using the SGI-5 strictly to adjust the VSS signal before it hits the ECM. On that year TPI, the cruise and speedo are fed after the ECM, IIRC, so adjusting the source lets all else be correct.

Or, an aftermarket VSS that threads onto a mechanical driven gear like a 1985 model has would be another way to go. Maybe save that option if your VSS dies.

Green89IROC305

Thanks for the great information. If Hawkes cannot find one by Thursday I'll be ordering the 37.

Drew

iTrader: (58)

You'll notice from the chart that 3.08 gears weren't offered in 91 with a 245/50R16 tire. But that's not a huge deal since there's not much difference between a 245/50 and any other stock size tire. If there was everyone changing wheels and running whatever tires would have a speedometer reading way off. In the world it really doesn't matter that much.

There is a much bigger gotcha to keep in mind... Note the column for "Sleeve or Sensor". The long and short of it is there are two different VSS just like there are different sleeves for cable speedometer cars. The VSS has to match the driven gear, or you'll have issues.

So for myself anyway, it's easier to start at the most expensive part and work your way back. So which VSS do you have? That will tell you which driven gears you can use, and then you can work your way back to a drive gear that will read right.

rt66er

iTrader: (2)

FYI: if you do need to change to the 10456022 VSS (as I need to since I'm swapping to 3.23 posi), the part number listed in the above chart is discontinued. It has (supposedly) been replaced with ACDelco part number 10456089, which is available from Amazon (where I got mine a month ago, though not yet installed):

Drew

iTrader: (58)

Actually... If you're swapping from 2.73 to 3.23 in the 90 Firebird in your user profile, you need ACDELCO 213197 {#10456088}. Just as a general rule, from what I understand, the white VSS is for 2.73-3.08 gears, and the black VSS is for 3.23-up.

Here's the 90 Firebird chart too, just for fun.

Green89IROC305

This is the sensor I have:

BWD VSS S8033

I'm pretty sure this is right, as it not only fits perfectly, it is nearly identical to the cable driven unit I pulled out of the trans. This trans was originally paired to a 3.23 posi axle.

Drew

iTrader: (58)

Yeah, that really doesn't count for much. The tail shaft housing doesn't care if it's got the right VSS or speedometer gear sleeve, they're all physically the same size. The difference is how the sensor positions the driven gear. To get the right sensor, GM used the RPO codes.

BWD S8033 crosses over to GM #10456088. 10456088 is just a later number for #10456021 in the chart. 10456088 will work with driven gears Q, R, or S. So we look for Q, R, and S in the chart... S is 3.23, Q, and R are for 2.73. So you need a red drive gear, and a red or blue driven gear.

Green89IROC305

I still feel like I am missing something, perhaps its because of me poorly communicating the years and configurations of components I am putting together. To that end I will reiterate what I am using and its origins.

I am building a 91 Z28. It originally came with a 305 lb9, T56, 245/50/16 and 3.08 posi axle. I got it as a roller.

I used my 87 IROC as a donor(everything rotted out around the drivetrain) it originally came with 305 lb9, 700R4, 245/50/16 and 3.23 axle.

Why would I need to swap out the Grey 15 tooth drive gear already in the transmission I am using? Will 10456088 and a 36 tooth 25513043 not mesh with the drive gear already in it?

If I need to replace the drive gear I will.

Given what has been said, I think I can conclude I have the right VSS for the original application.

What's remaining would be which driven(possibly drive gear too) to get.

Based on the sticky here at Thirdgen, and several calculators, with 245/50/16 and a 15 tooth drive gear along with 3.08 axle, 36 tooth is what I want.

Thanks for the help guys.

rt66er

iTrader: (2)

Hmmm. According to the chart you posted, a 3.23 gear with 245/50-16 tires calls for A (17 tooth) drive gear and T (44 tooth) driven gear. The chart shows 10456089 VSS for T driven gear. My understanding is the 10456089 accepts 40 tooth or more driven gears, while the 10456088 accepts 30-39 tooth driven gears. Please correct me if I'm wrong.

Drew

iTrader: (58)

I'm just giving you the answer suggested by GM. Logically what you've got worked out sounds like it'd work. You're just working with data that's not in the chart. Who's to say exactly why GM didn't use that combo.

Drew

iTrader: (58)

I think you're right. The heat must be getting to me, sorry.

Green89IROC305

I do appreciate the answers you have provided. The intention behind that question was to make sure there wasn't something I was missing that could lead to something awful down the road. I would switch the drive gear if it were necessary for fitment otherwise I'd prefer to leave 30 year old plastic gears lie.

Drew

iTrader: (58)

I think you're probably fine doing it that way. I know in some cases when you get to the razors edge of the gears range, it can stress the gear and lead to accelerated wear, but that's not necessarily why the chart doesn't show the 36T. It could be as simple as just trying to keep things simple for the service dept, or limit the inventory of service parts, etc. Worst that could happen is that some issue could come up, but it'll probably be fine.

jmd

iTrader: (4)

I forgot the two sizes of VSS. What was on the VSS before? If it was 36-39, you are good with a 36 or 37 for sure.

Green89IROC305

Originally this transmission had a cable driven speedometer.

What was into this pictured below.