72 Turbo Hydromatic Speedo Housing ??? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

sick472 · 08-26-2018, 01:32 PM

I have a TH-400 in my 72 Truck behind a Pontiac 400 motor. I believe the tranny and motor combo can from a 72 car. Anyhow, After several years in boxes the thing is going back together and for some reason I have two different speedometer gear housings. They both are from TH400 trannies, I think, and appear that either one would work in the transmission. One is pretty basic and the other has a wire coming out it. I am not worried about the gear tooth at this point, I'll figure that out as tires get selected.

Any comments on which one might be better to use and/or what the wire is for?

sick472 · 08-30-2018, 10:24 AM

Just a bump...anybody out there before I have to learn the hard way? Thanks!

geezer#99 · 08-30-2018, 10:37 AM

What’s the hard Way?
I think the one with the wire is for a speed sensor.
Use the one without the wire because you know you can get different gears for it.
Done deal!

**HO455** · 08-30-2018, 03:42 PM

I believe the wire is for speed sensing to a cruise control. Both will work but you may find that one is different than the other in regards to which speedometer gear you can run in it. There are two or three different ones depending on what rear end ratio and tire size you have. Each housing (of the no sensor style) has several numbers in the casting telling you what gears can be used in the housing. Here is a link that should help you figure out if there is a better one to pick from a speedometer error stand point.

http://www.tciauto.com/tc/speedometer-gear-calculator/

PS. Do you have any pictures of your motor mounts you could share?
Thanks in advance.

sick472 · 08-31-2018, 10:53 AM

Thanks for the confidence boost folks!

Geezer, the hard way might just be guessing which one to use just to find out that it self destructs. Ignorance is not always bliss, hence the posted question.

Just for informational purposes...The sensor housing is for 35 to 39 tooth and the other is 36 to 39.

Thanks for the extra info and link HO455! Pm Sent regarding the mounts.

chewychevy67 · 03-10-2022, 07:24 PM

Do you still have this sick472? Any chance you could post some pics of that red gear on the one with the wire? Ever find out what it is used for.? I got one and I ordered this gear but I'm not sure it is my answer. Yours looks different a bit.

sick472 · 03-11-2022, 09:11 AM

Quote:

Originally Posted by chewychevy67

Do you still have this sick472?

I think I do. I will look this weekend. Do not hesitate to PM me a "Hello" as a reminder. I will be in the shop all weekend, but may forget while focusing on a big project I have going on. I'll be more than glad to help.

There are some obvious differences between yours and mine, but I'd bet they are purely looks and don't effect function...we will see, I guess.

sick472 · 03-11-2022, 09:22 PM

I have no idea where I came up with this gear and housing. It is a 400 TH piece, but it either came from a 72 unit or came to me mysteriously. Here are some pics and measurements...

3rd pic, 0.968" in overall height,
4th pic, 1.515" OD,
5th pic, 0.474 tooth thickness.

Let me know if you need more info!

chewychevy67 · 03-12-2022, 05:37 AM

Thanks for the pictures. I am waiting to receive the gear in the mail. I looked fr some time to find one that looks like yours. When I receive this one I will outfits measurements hee as well. I sure hope it works but it looks like it may sit shallower than yours.

chewychevy67 · 03-12-2022, 12:41 PM

If your not using the gear setup and If you would be interested in selling that housing and gear I would be interested in it. I would rather have a part that I know will be correct. The one I purchased says its for a 700r4 with vss and I'm noontime convinced after seeing yours closer that it will fit properly.

Accelo · 03-12-2022, 03:50 PM

Chewychevy67
The 700R4 speedometer housing and the THM400 require the same housing. Yours should fit. However, you need to know the tooth count of the required gear as their are two different gear housing. They have two different offsets to accommodate the different gear diameters.
They come in -36/39 & 40/43 (defined by the # gear teeth on the plastic gear)

chewychevy67 · 03-12-2022, 05:17 PM

Yes I have the proper housing. I need the 37 tooth gear which is what he has here and what I have coming. It just looks like there is quite a difference in the way the 700r4 gear is shaped

chewychevy67 · 03-29-2022, 04:33 PM

Do my gear is shaped with a d and the th400 housing has a squared off shape so it doesn't fit. I took zoomed in pic of the pic sick472 took and it's shaped with 2 flat edges

08-26-2018, 01:32 PM	#1
sick472 Registered User Join Date: Jul 2015 Location: Sedalia Mo. Posts: 1,130	72 Turbo Hydromatic Speedo Housing ??? I have a TH-400 in my 72 Truck behind a Pontiac 400 motor. I believe the tranny and motor combo can from a 72 car. Anyhow, After several years in boxes the thing is going back together and for some reason I have two different speedometer gear housings. They both are from TH400 trannies, I think, and appear that either one would work in the transmission. One is pretty basic and the other has a wire coming out it. I am not worried about the gear tooth at this point, I'll figure that out as tires get selected. Any comments on which one might be better to use and/or what the wire is for? Attached Images __________________ He who is without oil shall throw the first rod. Compressions 8.7:1 1972 C10 1976 C10 (parts truck) 1985 K20

08-30-2018, 10:24 AM	#2
sick472 Registered User Join Date: Jul 2015 Location: Sedalia Mo. Posts: 1,130	Re: 72 Turbo Hydromatic Speedo Housing ??? Just a bump...anybody out there before I have to learn the hard way? Thanks! __________________ He who is without oil shall throw the first rod. Compressions 8.7:1 1972 C10 1976 C10 (parts truck) 1985 K20

08-30-2018, 10:37 AM	#3
geezer#99 Registered User Join Date: Aug 2009 Location: Bowser Posts: 13,515	Re: 72 Turbo Hydromatic Speedo Housing ??? What’s the hard Way? I think the one with the wire is for a speed sensor. Use the one without the wire because you know you can get different gears for it. Done deal!

08-30-2018, 03:42 PM	#4
HO455 Post Whore Join Date: Feb 2016 Location: Portland Oregon Posts: 10,805	Re: 72 Turbo Hydromatic Speedo Housing ??? I believe the wire is for speed sensing to a cruise control. Both will work but you may find that one is different than the other in regards to which speedometer gear you can run in it. There are two or three different ones depending on what rear end ratio and tire size you have. Each housing (of the no sensor style) has several numbers in the casting telling you what gears can be used in the housing. Here is a link that should help you figure out if there is a better one to pick from a speedometer error stand point. http://www.tciauto.com/tc/speedometer-gear-calculator/ PS. Do you have any pictures of your motor mounts you could share? Thanks in advance. __________________ Thanks to Bob and Jeanie and everyone else at Superior Performance for all their great help. RIP Bob Parks. 1967 Burban the WMB,1991 S(stink)-10 Blazer,1969 GTO, 1970 Javelin, 1952 F2 Ford 4X4, 29 Model A, 72 Firebird. 85 Alfa Romeo If it breaks I didn't want it in the first place The WMB repair thread http://67-72chevytrucks.com/vboard/s...d.php?t=698377

08-31-2018, 10:53 AM	#5
sick472 Registered User Join Date: Jul 2015 Location: Sedalia Mo. Posts: 1,130	Re: 72 Turbo Hydromatic Speedo Housing ??? Thanks for the confidence boost folks! Geezer, the hard way might just be guessing which one to use just to find out that it self destructs. Ignorance is not always bliss, hence the posted question. Just for informational purposes...The sensor housing is for 35 to 39 tooth and the other is 36 to 39. Thanks for the extra info and link HO455! Pm Sent regarding the mounts. __________________ He who is without oil shall throw the first rod. Compressions 8.7:1 1972 C10 1976 C10 (parts truck) 1985 K20

03-10-2022, 07:24 PM	#6
chewychevy67 Registered User Join Date: Jan 2010 Location: Here Posts: 5,413	Re: 72 Turbo Hydromatic Speedo Housing ??? Do you still have this sick472? Any chance you could post some pics of that red gear on the one with the wire? Ever find out what it is used for.? I got one and I ordered this gear but I'm not sure it is my answer. Yours looks different a bit. Attached Images

03-11-2022, 09:22 PM	#8
sick472 Registered User Join Date: Jul 2015 Location: Sedalia Mo. Posts: 1,130	Re: 72 Turbo Hydromatic Speedo Housing ??? I have no idea where I came up with this gear and housing. It is a 400 TH piece, but it either came from a 72 unit or came to me mysteriously. Here are some pics and measurements... 3rd pic, 0.968" in overall height, 4th pic, 1.515" OD, 5th pic, 0.474 tooth thickness. Let me know if you need more info! Attached Images __________________ He who is without oil shall throw the first rod. Compressions 8.7:1 1972 C10 1976 C10 (parts truck) 1985 K20

03-12-2022, 05:37 AM	#9
chewychevy67 Registered User Join Date: Jan 2010 Location: Here Posts: 5,413	Re: 72 Turbo Hydromatic Speedo Housing ??? Thanks for the pictures. I am waiting to receive the gear in the mail. I looked fr some time to find one that looks like yours. When I receive this one I will outfits measurements hee as well. I sure hope it works but it looks like it may sit shallower than yours.

03-12-2022, 12:41 PM	#10
chewychevy67 Registered User Join Date: Jan 2010 Location: Here Posts: 5,413	Re: 72 Turbo Hydromatic Speedo Housing ??? If your not using the gear setup and If you would be interested in selling that housing and gear I would be interested in it. I would rather have a part that I know will be correct. The one I purchased says its for a 700r4 with vss and I'm noontime convinced after seeing yours closer that it will fit properly.

03-12-2022, 03:50 PM	#11
Accelo Registered User Join Date: Mar 2015 Location: washington Posts: 2,161	Re: 72 Turbo Hydromatic Speedo Housing ??? Chewychevy67 The 700R4 speedometer housing and the THM400 require the same housing. Yours should fit. However, you need to know the tooth count of the required gear as their are two different gear housing. They have two different offsets to accommodate the different gear diameters. They come in -36/39 & 40/43 (defined by the # gear teeth on the plastic gear)

03-12-2022, 05:17 PM	#12
chewychevy67 Registered User Join Date: Jan 2010 Location: Here Posts: 5,413	Re: 72 Turbo Hydromatic Speedo Housing ??? Yes I have the proper housing. I need the 37 tooth gear which is what he has here and what I have coming. It just looks like there is quite a difference in the way the 700r4 gear is shaped

03-29-2022, 04:33 PM	#13
chewychevy67 Registered User Join Date: Jan 2010 Location: Here Posts: 5,413	Re: 72 Turbo Hydromatic Speedo Housing ??? Do my gear is shaped with a d and the th400 housing has a squared off shape so it doesn't fit. I took zoomed in pic of the pic sick472 took and it's shaped with 2 flat edges Attached Images



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