Transmissions and DrivetrainNeed help with your trans? Problems with your axle?
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alright im SO ready to get my speedometer working. from my understanding the th350 driven gear will work in the t-5, i need to know how to find out what the DRIVE gear is in my transmission?
i talked to a guy at the gm dealership today and he told me i need a 20 tooth driven gear but idk what drive gear that was for..
if there is a chart or something on the net that i could look at i would really appreciate it. i have factory size tires and 3.45 rearend gear ratio.
__________________ Numquam ponenda est pluralitas sine necessitate. — William of Ockham, from Quaestiones et decisiones in quattuor libros Sententiarum Petri Lombardi
Roughly paraphrased into modern English, and applied to figuring out what's wrong with your car:
The simplest explanation that fits all the facts is probably the right one.
and i need the 20 tooth driven gear to match up with that 7-tooth drive gear correct? and that is the site i was looking at earlier it didnt saw anything about the th350 drive gear working in the t-5 but it did say the driven gear is interchangable in the t-5 and the th350. now to change out the drive gear i have to remove the entire tailshaft correct?
No you don't have to remove the tail shaft (not least because a manual transmission doesn't have one...) but you do have to remove the extension housing. Which is a casting, not a shaft.
Yes you need the 7 & 20 combo.
__________________ Numquam ponenda est pluralitas sine necessitate. — William of Ockham, from Quaestiones et decisiones in quattuor libros Sententiarum Petri Lombardi
Roughly paraphrased into modern English, and applied to figuring out what's wrong with your car:
The simplest explanation that fits all the facts is probably the right one.
very nice that post on thirdgen should be a sticky on this board i looked every where for information on this. would have been SO easy when i had the trans out of the car a month ago.... im not doing all that work to change the drive gear so i hope the one in there is right, ill just put on the driven gear and hope that works
Background: 84 Z28 with a T-5 and 3.73 gears. Stock speedo gears are a 7 tooth purple drive gear and a 21 tooth red driven gear PN 3987921.
I had a leak from the seal that goes around the speedo gear, so I installed a new speedo gear sleeve PN 345215. It was dimensionally identical to the original although it looked a little bit different.
Later I installed 3.42 gears and I wanted to recalibrate the speedo. I needed a 19 tooth white driven gear to match with my 7 tooth drive gear. According to numerous posts on TGO, the part number for that gear was 14090592. However, when I received this gear, it was different from my original gear:
1) the new gear has a metal shaft, the old gear was all plastic
2) the new gear is 1/4" longer than the old gear
3) the "hub" on the back side of the new gear (the part that goes into the trans first) is 1/2" in diameter vs 1/4" on the old gear
4) the diameter of the new gear where it meets the seal in the sleeve is 0.312" vs 0.308" for the old gear
Despite all this, I installed the gear since it was supposedly the right one. The result was a leak from the speedo sleeve and my speedometer worked very erratically.
I removed the metal shaft gear and reinstalled my original gear. The speedo went back to working correctly (albeit not calibrated for the 3.42s), but the new gear apparently damaged the seal in the sleeve because there was still a small leak.
I then ordered a new sleeve and an all plastic 19 tooth white speedo gear PN 3987919. The speedo is now working correctly, calibrated for 3.42s and no leaks.
So the question is: what is the deal with the metal shaft T-5 speedo gears? Are they for later model T-5s with VSS senders? Or is there a different sleeve than the PN 345215 that works with the metal shaft gears?
For future reference, here are the PNs for the all plastic T-5 speedo gears:
Teeth PN Color
18 3987918 Brown
19 3987919 White
20 3987920 Blue
21 3987921 Red
22 3987922 Gray
The gears are about $5.50 each from the dealer, or half that from GM Parts Direct although they come in bags of 2. Beware of clowns on ebay selling these things for $15 each...no reason to pay that much for them.
Here is a picture of the metal shaft vs. all plastic gear along with the original speedo gear sleeve.
jamesc i have a couple questions for you on this b/c you seem like you have done this stuff before...
i am changing from an electrical vss to a mechanical setup. i havent taken the electrical one off the t5 yet b/c i drive my car everyday so idk if it is the gear with the metal shaft or the full plastic gear. and also (on http://www.transmissioncenter.net/sp...n_______va.htm) it says the speedo gear hosing from the th350 will work.. but it is like metal the one off my automatic was plastic, and i looked at my neighbors t-5 and it was plastic. to make it simple i need the correct speedo gear housing for a t-5 and i need the correct speedometer gear in 20 tooth blue. but idk if i need the one with the metal shaft or the all plastic one. can you help me out?
here is the part of that website that was talking about the th350 speedo gears and housing (says it will work with the t-5)
-----------------------------------
68X. Speedometer gears for a Chevy TH350 transmission with 26 inch tires and 4.10 gears. 7 tooth drive gear and 22 tooth driven gear. Cost $19.00 for both. We also have 8, 9 and 10 tooth drive gears, and 17, 18, 19, 20, 21 and 22 tooth driven gears. (The driven gears also fit Super T-10 and Chevy T5 transmissions.)
#68XX. Chevy TH350 speedometer gear housing, comes with both seals, no gear. (If you have an aluminum housing it needs to be replaced with this steel housing.) (Also fits T-5 and Super T-10.) Cost $9.00
Qty 12345
Only to say that I used a new "plastic" gear with a new sleeve. I experienced no difficulties.
JamesC
can you point me in the right direction of the new sleeve? i looked that part # up on gmpartsdirect but no luck. im not sure if the sleeve from the site that i posted will work or not.
__________________ Numquam ponenda est pluralitas sine necessitate. — William of Ockham, from Quaestiones et decisiones in quattuor libros Sententiarum Petri Lombardi
Roughly paraphrased into modern English, and applied to figuring out what's wrong with your car:
The simplest explanation that fits all the facts is probably the right one.
