So, my speedometer cable broke and when it did, it destroyed the speedometer housing with it, broke the threaded neck clean off. I am having the hardest time finding a replacement housing because all the ones I find are for replacing those with a plastic shaft for the gear, but mine is metal and doesn't work with those housings. Anyone have any idea where I can find the correct housing?

 

Oh, it's a 700R4 and the gear here has 38 teeth. The one on the shaft in the transmission was red and the car had 2.73 gears originally.

 

You might have to buy a new housing that accepts the plastic gear... Have you contacted any of your local transmission shops?

 

I haven't, I wanted to see what I could find here. My concern is if I need the metal shaft due to the car having cruise control and a 2 piece cable, plus I don't know if the length is right for the plastic ones. I don't want to have another cable break if I do something wrong..

 

Looks like yours is original. My wife's 1987 was like yours. Metal shaft with plastic gear, two piece speedo cable. My speedo cable got stuck and sheared the cable. Ran into your same problem finding replacements.
Easiest s solution was buying a new housing and newer style all plastic gears, then a one piece cable. Works great now.
I went with something similar to this:
https://www.ebay.com/itm/TH400-Speedometer-Driven-Gear-complete-Set-40-41-42-43-44-45-tooth-Housing/172661521980?_trkparms=aid%3D1110006%26algo%3DHOMESPLICE.SIM%26ao%3D1%26asc%3D225118%26meid%3D2909b0ac87004cc3822af3089b641c77%26pid%3D100935%26rk%3D1%26rkt%3D12%26mehot%3Dag%26sd%3D173812226098%26itm%3D172661521980%26pmt%3D1%26noa%3D0%26pg%3D2332490%26algv%3DSimplAMLv5PairwiseWebWithDarwoV3BBEV2b%26brand%3DUnbranded&_trksid=p2332490.c100935.m2460

I probably have the old housing still kicking around. My old one is still good. Shoot me a message with your zip code. Maybe I'll just ship it to you.

 

I had heard the 2 piece cable was required for cruise control to be functional. I have no idea how that works, but hey. Did you have cruise before and does it still work okay now? I already bought a 2 piece cable replacement, I would hope that would still work fine!

 

Mine has cruise control and replacing with one piece cable did not affect it. Still works with one piece cable.

 

Here is one with the new housing and 38 tooth gear. Or shoot me zip code. I'm sure I still have my working old style in a parts bin.
https://www.ebay.com/itm/700R4-Trans....c100935.m2460

 

Ah, that looks like one I was looking at! If I put a different gear in there, I was going to put the 40 tooth one in, since it would correct my speedo error. If everything worked out fine for you, I might just order the one I found, stick it on, and see if it works with the two piece cable. If it doesn't, cables aren't particularly expensive for the one piece and I'll get one of those. Now, if I can just get the second hand cable I bought separated, I can clean it up and regrease it....

 

Oh, and did you have the old style housing you mean? I have no idea why they designed it like that, the whole thing seems ridiculous.

 

That is not an "Odd-Ball" speedometer housing.

Plastics housings were used, as well as aluminum.

Plastic gears separate, with a metal shaft were used, as well as a solid plastic gear and shaft assembly.

 

If it's not an oddball, why can't I find it for sale anywhere? Or did the transmission guys tell me wrong that the metal shaft meant it needed a unique housing from the plastic shaft ones?

 

If you are having trouble finding these for the THM700-R4...

Search for the same tooth-count gear for a THM350... as they are more common.

 

Your transmission guy is correct. The metal shaft gear needs the older style plastic housing. The all plastic gears use the newer style aluminum housing. I discovered the two types of gears do not in interchange with the housings.

If you get new I recommend you get a set of speedo gears so you can experiment with different tooth count to make your speedo precise. Using one of those tire/ratio size calculators is hit or miss for whether you will find the right speedo gear. The cable driven speedometers work by a rotating magnet. As the magnet ages it loses strength, which causes the speedometer to lose accuracy. You can correct this by experimenting with different tooth count gears. I tried to use the speedo calculator and had people on this forum promise me it would work. It didn't, because no formula can calculate the rate your magnet loses strength. In the end I ordered a set of gears and experimented until I found the right size. For my particular rear gear ratio I discovered each gear made about 1.5-2 mph difference. Your gear ratio may be different.

Later I swapped in another speedometer from an exact year car. Same 145mph speedo too, but I discovered an immediate difference of about 4mph compared to the other speedometer, even though they were exact same style and age. Moral of the story: magnets age and speedometers lose accuracy. Get a pack of different speedo gears.

Also, I wouldn't reuse a 30+ year old cleaned up two piece cable. My two piece worked perfect right up until it sheared. Get brand new for $20 and not worry about tearing up your other new parts with an old cable that is ready to blow.

 

Yeah, apparently the old style was recalled! That's why no one seems to sell them anymore. And I already spent $45 on a used two piece that I can't return because someone else had said that cruise control cars had to have it. This sucks, because I'm really broke right now with COVID, I don't have money to blow. At all.

 

As Aaron said (which I did not think to mention), if you need another metal-shaft + plastic gear....
And you are looking for them from transmission cores...

Look for a THM350 with a Chevrolet Bell-housing and a plastic speedometer housing.
This would be the most common way to find these parts.

BOP versions of the THM350 will uses a different type of speedometer arrangement.

 

Hi:
Is there any GM Reference for a GM Part Number for the Speedometer Gear Housing Sleeve ? After calling a few Transmission shops, I was able to find a Used one, I brought the old one with me to match exactly. Would like to have a spare if possible ?

I would Highly Recommend call your local Transmission shops first and go from there. Apparently there a 2 Versions, one has a Longer Neck and the OEM one that is shorter, defintely bring you old one with you and match it exactly and your good.

The first 2 pictures is the USED one I bought, they also gave me the Housing Seal and the Shaft Seal. The One on the white paper towel is the OEM one