Need Th350 Speedo Part..

[FRENCHBLUE72]

Really need the little speedo gear that slide's into the rear if the tranny anyone have one they want to get rid of.......

[Longhorn Man]

Any idea what color the old one was? It determines the tooth count, and in turn (no pun intended) the speedo reading.
I have a tan one...no idea what they go for.

[Harold Shepard]

Which gear do you need? Part that is on the tailshaft or the piece driven by the one on the tailshaft and if it is the first one is it metal or plastic? Have you checked with your chevy dealer? They have them and they (if they will) can look them up on the computer- all have the program- some won't use it. Harold

[67sss]

are you looking for this part?

[FRENCHBLUE72]

I am not sure what color the gear was as there is just a big hole where the speedo cable should thread onto the clamp is still there just the assembly that slide's into the tranny is gone.. Yess sss the appear's to be what I am looking for but I notice there are different length's in the picture(differnt tranny's or all for the th350?) If anyone has one that would work for my application it would be greatly appricated..

[PT'S 70 CST]

Like Longhorn man said you can still get these from your local GM dealer, if you know what gear you are running in your rear end they can match you up with the one you need. You will need to know what gear it is or it will throw your speedo reading off. If I am not wrong I think I have a new one for a 411 in the shop I bought for my Nova and it want see the road for a while, if you need it I will call my buddy at the GM dealership in town and find out what I paid for it and you can have it for that if you need.

PT

[Tx Firefighter]

Couple of things....

1) Those items in the picture are called speedometer bullets. They are all different looking, but they all interchange. You don't want an aluminum one. The aluminum ones wear and get sloppy and start to leak. The one on the very left is a steel one. That's the kind you want.

2) You can't just buy a speedometer driven gear for your rear end ratio. You have to know which gear is inside the transmission. It's a ratio, not just one gear. For example, you may have a 40/18 or a 38/17 or whatever. There are several different gears that could be right, and you don't know which until you determine what drive gear you have inside the trans.

3) A 4:11 geared Nova will probably use a much different set of speedometer gears than a 4:11 pickup does. The Nova will likely have shorter tires than a truck, which makes the difference.

[/<eystroke]

Post your wheel diameter and rearend ratio and we can tell you what gears you need.

[FRENCHBLUE72]

TX unfortunatly I don't know anything about the trans it came with the truck if I get the # off the tranny would that help me out??? I can go measure the wheel dia and find out the gear ratio in the rear end if that will help me???

[FRENCHBLUE72]

The tire's are p235/75 r15 goodyear's...
The yoke turn's 1 1/2 turn's for every full rotation of the tire I had to do ti old skool because I could not find a tag on the housing...
The little gear inside of the tranny that I could see was white here are a few pic's I took to make sure I am talking about the right part..
My finger is stuck in the hole I am needing the part for...

[Robert1970C20rstbukt]

Yep, that hole is for your speedometer driven gear. The drive gear is inside the *tailhousing*, so if you wanted to check the # on the drive gear you'd need to pull the tailhousing.

[kingsolver72]

I am sorry for jumping in but,I'm a little confused.This is what I have on my 350.Are the gears everyone is referring to inside the housing that is on my tranny? I know I probably seem foolish.I hope that I have not clouded things up.

[Tx Firefighter]

To tell how many teeth your drive gear has, you need to pull the tailhousing off the trans...not pull the mainshaft like was mentioned above.

kingsolver, that deal on your trans is an adapter box sometimes used to correct speedometers for weird applications. Not too commonly seen anymore. Underneath it, is where the trans speedometer gears are. That box unscrews off your bullet (see picture of 3 bullets above).

[Robert1970C20rstbukt]

To get to your speedometer driven gear, remove that little box that is off to the side on the tranny, that's the part that he's looking for. If you wanted to get to the drive gear, remove the tailhousing. I made a typo in my other post, I meant tailhousing. FYI, there are two gears that work the speedometer: a drive gear, which is about 2 inches in diameter and about 1/2" wide, and the driven gear, they're the smaller ones pictured above.

[Tx Firefighter]

Frenchblue, your tailhousing is held on by 4 bolts. I can see two of them in the pictures you posted. Just unbolt it and tap the housing slightly and it will pop right off the transmission case. Some fluid may come out, but that it, no rocket science.

Once you have the housing off, the gear will be right there on the shaft. Can't miss it.

[/<eystroke]

Frenchblue72:
Sounds like you have a 3.07 rear end. Your 235/75 15 tires will have a diameter of 28.8".
I used 28.5" in my calculator for tire squat.

Here is a list of gears that should get your speedo close. These gears are available at
most GM Dealerships. The drive gear is on the transmission shaft, and is the harder one
replace. The driven gear and housing is what you are missing, which is simple to
install. There are 3 different size housings for a TH350. The numbers below under
housings are TCI part numbers, not GM part numbers. http://www.tciauto.com

If you know the GM Part number, you can order it online here.
http://www.gmpartsdirect.com

   Finding best gear combo for your TH350 Transmission with 28.5 tires and
    3.07 rear end...

    Sorted best to worst.
    Drive Gear            Driven Gear           % off
    17 (red)              37 (red)                  0.18
    18 (blue)             39 (brown)               -0.26
    19 (yellow)           41 (yellow)              -0.67
    20 (brown)            43 (purple)              -1.04
    20 (brown)            44 (dark gray)            1.25
    19 (yellow)           42 (green)                1.72
    18 (blue)             40 (black)                2.23
    17 (red)              36 (white)               -2.58
    17 (red)              38 (blue)                 2.80
    18 (blue)             38 (blue)                -2.90
    19 (yellow)           40 (black)               -3.19

TH350 Drive Gears:
Teeth   Color   GM PN      Notes                   Clip 
8       Black   6261783    1.19" shaft, Style A    5/16" clip, 880024
10      Purple  6261785    1.19" shaft, Style B    5/16" clip, 880024
18      Green   6260037    1.19" shaft, Style C    7/16" clip, 880026
19      Natural 8640188    1.19" shaft, Style C    7/16" clip, 880026

TH350 Driven Gears:
Teeth   Color   GM PN      Notes                           Housing
18      Brown   3987918    2.25"x.305"x.785", Style F      880021
19      Natural 3987919    2.25"x.305"x.800", Style F      880021
20      Blue    3987920    2.25"x.305"x.800", Style F      880021
21      Red     3987921    2.25"x.305"x.800", Style F      880021
22      Grey    3987922    2.25"x.305"x.810", Style F      880021
34      Green   9774413    3.35"x.305"x1.500" Style H      880022
35      Orange  9780387    3.35"x.305"x1.500" Style H      880022
36      Natural 1359270    3.35"x.305"x1.500" Style H      880022
37      Red     1359271    3.35"x.305"x1.500" Style H      880022
38      Blue    1359272    3.35"x.305"x1.500" Style H      880022
39      Brown   1359273    3.35"x.305"x1.500" Style H      880022
40      Black   1362048
                25513047   3.35"x.325"x1.670" Style H      880023
41      Yellow  1362195    3.35"x.325"x1.670" Style H      880023
42      Green   1362049
                25513049   3.35"x.325"x1.670" Style H      880023
43      Purple  1362196
                25513050   3.35"x.325"x1.675" Style H      880023
44      Grey    9780470    3.35"x.325"x1.670" Style H      880023
45      Lt Blue 9775187    3.35"x.325"x1.690" Style H      880023