I'm trying to remove the speedometer cable on my 1972 Cutlass TH-350 transmission, to get the gear out. The speedometer shop is telling me there is another gear, attached to the driven gear that has 8, 9, or 10 teeth on it, and they need to know what it is.

I can't seem to get the cable out, does the housing have to unbolt first? I bought an "O"-ring to replace the drip, but can't seem to figure out how to get it off. I tried vice grips on the silver circular part you see in the picture to no avail. Am I doing something wrong?


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I'm not seeing that in the 72 CSM. If you have it, look at Page 4B-35. Page 4B-37 shows the TH350 Drive gear is an 18 tooth. For 3.23 gears (I think that's what you're are from a previous thread?) it will depend on your tire size.

The standard tire back in 72 was the F78/14. The driven gear would be 45 teeth and light blue in color.

The next size up is G78/14. Driven gear is 44 teeth and is Dark Grey
Performance G70/14. Driven gear is 45 teeth and is Light blue in color. NONE of these gears require an adapter.

Is your leak coming from the sleeve or transmission cable itself?

Don't know if this helps you or not.

 

I'm looking at the same page, and I agree I don't see any 8, 9 ,or 10 tooth gear listed. The guy told me there are 4 speedo related gears in there. I figured I would remove the cable and see. But I can't seem to figure out how.

The 40+ tooth count gears apparently require a different housing as they are bigger. There is an Olds housing for 335-39 teeth and from 40-4x teeth).

The leak seems to be coming from that silver connector, and dripping down. But I can't seem to get it off.

 

Should be able to use a pair of pliers to get a grip on it and turn it up (left) to loosen. Then it should come off fairly easily. Same kind of connection as used on Cruise control. The connection is threaded so it should be easy to remove. You might want to spray that area with brake clean first so your pliers don't slip on the trans fluid.

You're lucky. I'm just about to get into mine. Last time it was touched was back in 1984 and it's got a lot of accumulated yuck on it. The good thing is it's not leaking, but I need to remove the sleeve so I can put in the gear for my 3.42's. When I took out and redid my driveshaft last year, the car puked out about 2+ pints of tranny fluid so I seriously doubt I'll run into any drips when I take that apart.

 

I'll try again, cleaning it off better, like you suggested. At least now I know it's threaded, so I'm going at it the right way.

What do you mean remove the sleeve? I'm going up 3 "steps" on the gearing chart, so my new gear is bigger as well, I might have to do the same.

 

The bolt on the retainer holds the sleeve in place. The driven gear shaft goes through the sleeve to the speedo cable so you need to remove the sleeve to get the old speedo gear out anyway if I'm seeing this right. What I don't know is whether there's a seal on the sleeve or in the trans casing to prevent leaks. Looking at your pic though it appears that something there is leaking and it might be related to that or the speedo cable connection?

I want to clean that up first on my car before I start taking anything apart to avoid any possible contamination. Hmmm, I just noticed something. The chart in the CSM doesn't show a TH350 with 3.42 gears, but it does for the TH400. I wonder if that means I need to get a new sleeve to accomodate that change from 30's driven teeth (old was 2.73 gears) to 40's teeth. Crap! Now I need to check my new speedo gear to see exactly how many teeth on the driven gear. I bought the thing over 5 years ago from a guy on ebay who did the calculations for me based on 3.42 gears and 225/70/14 tires.

 

The inside of the "sleeve" should have a small o-ring in there I believe so fluid doesn't leak passed it.
The speedometer gear housing will have some numbers stamped on it. Those tell you what tooth gears it will take. If you need to go outside of that range, you need to swap gear housings.
Here is a pic of the drive and driven gears for specific transmissions, rear end ratios and tire combos:
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Randy, that's a different chart than what I have in my 72 manual. Is that by any chance from 1970? Second question - Is the reference to 3 speed column for AT or column shift manual??

 

Yes it's a 70 and it's for a manual trans. Notice the column on the right is listed as "Hydra-matic" and not TH350 or TH400.

 

That's why I was asking. In my 72 manual it's broken out for TH350 and TH400. Thanks Randy.

 

Back to removing the speedo gear:

You do not need to remove the cable from the gear housing (sleeve), although you can if you want to.

The cable is held to the housing by a threaded collar, and, as you can see, this area picks up a lot of oil, and a lot of road dirt. This combination created a sort of gravelly cement, which infiltrated the threads of the threaded collar, and can make it very hard (and crunchy) to turn, but turn it will, if you are determined.
Be careful not to clamp down too hard on the collar and deform it too much.

The housing (sleeve) is held in the transmission by a flat plate that slides into a groove on the housing and is held to the side of the transmission by a screw with a ⅜" head.
If you remove the screw, the housing and the retaining plate will both pull straight out of the transmission. You do not need to remove the speedo cable from the housing to pull it out, and it may be easier to pull out with the cable to grab onto.

The O-ring fits on the outside of the housing.

Have a bucket ready for when you pull the housing out of the trans.

- Eric

 

I think I have no choice. According to the 72 CSM I need a different sleeve for the 3.42 speedo gear. Not sure where to source the adapter though. Any suggestions?

I don't think I have enough left to create Niagara Falls when I take out my adapter. It puked out about 2 1/2 pints last year when the driveshaft came out. Still, a bucket is a good idea unless a guy likes cleaning floors.