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Thread: T-350 speedo gear question? Reply to Thread
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Topic Review (Newest First)
08-01-2012 02:47 AM
mmerlinn
Quote:
Originally Posted by mmerlinn View Post
As Crosley has noted, the driven gears depend on the tail housing used. Generally, but not always, the small hole type is used on Chevys while the large hole type is used everywhere else.
I meant to say:

As Cobalt has noted, the driven gears depend on the tail housing used. Generally, but not always, the small hole type is used on Chevys while the large hole type is used everywhere else.
07-31-2012 11:26 AM
mmerlinn
Quote:
Originally Posted by tobyj17 View Post
I haven't ordered the gears yet, but i did finally get the speedo hooked up, 30 mph off!

One thing i forgot to ask, are these gears the same with a TH350 and Th 350c?
30mph of when you are going 5mph is a whole lot different than 30mph off when you are going 100mph. Basically, without a reference point, 30mph is MEANINGLESS.

TH350 and TH350C output shafts are interchangeable back and forth, so all drive gears that fit one will fit the other.

As Crosley has noted, the driven gears depend on the tail housing used. Generally, but not always, the small hole type is used on Chevys while the large hole type is used everywhere else.
07-31-2012 07:04 AM
cobalt327 I just got an email from TCI that included info on speedo gears- possibly because of posting about them here at Hotrodders: Speedometer Gears - Transmission Accessories - TCIŽ Auto
07-31-2012 12:46 AM
cobalt327
Quote:
Originally Posted by tobyj17 View Post
I've got the large housing... so which gears does a person order?
I would contact Speedometer Gear, Speedometer Gears, Ford, GM, Dodge 700R4 or a similar company w/the knowledge to tell you what ratio of speedo gears to use along w/whether you need to use a different speedo gear housing (not talking about the whole tailshaft housing, just the part that holds the driven speedo gear). There's a calculator you can use to figure it out what gears you need, then check to see if the housing you have is compatible w/the needed gear.

Example of the gears available are also shown at http://www.areds.com/wp-content/uplo...rs-no-tags.pdf
07-30-2012 08:22 PM
tobyj17 I've got the large housing... so which gears does a person order?
07-29-2012 11:49 PM
cobalt327
Quote:
Originally Posted by tobyj17 View Post
Basically it sounds like I just need to pull it apart and see what I've got.. I didn't see any different gears that identified themselves as being for a TH350 or 350C.. I'll have to do some more digging.

Thanks!
In most all cases, you aren't going to find the wrong drive gear used w/the wrong tailshaft housing- but the possibility exists. It's prolly easier to keep the housing you have and match the correct drive gear to it if it's wrong. But like I say- that's going to be a rare occurrence. A glance will tell you if you have a large or small speedo housing:


Large housing


Small housing (upside down)
07-29-2012 07:48 PM
tobyj17
Quote:
Originally Posted by cobalt327 View Post
Too late to edit the last post, so I will try to clarify by saying that there are two size speedo gear housings that fit into two different tailshaft (extension) housings. Because the tailshaft housings will interchange, either tranny may now have either housing on it.

I don't think the gears pitch will allow a small housing driven gear to work w/a large drive gear or vise versa, if it did the speedo error would be huge.

The speedo gears will be in sets that have considerably different counts to them. You should be able to select the right size of gears by the driven gear housing size you have.

I hope this doesn't confuse the issue worse.

Basically it sounds like I just need to pull it apart and see what I've got.. I didn't see any different gears that identified themselves as being for a TH350 or 350C.. I'll have to do some more digging.

Thanks!
07-28-2012 01:50 AM
cobalt327 Too late to edit the last post, so I will try to clarify by saying that there are two size speedo gear housings that fit into two different tailshaft (extension) housings. Because the tailshaft housings will interchange, either tranny may now have either housing on it.

I don't think the gears pitch will allow a small housing driven gear to work w/a large drive gear or vise versa, if it did the speedo error would be huge.

The speedo gears will be in sets that have considerably different counts to them. You should be able to select the right size of gears by the driven gear housing size you have.

I hope this doesn't confuse the issue worse.
07-28-2012 01:06 AM
cobalt327
Quote:
Originally Posted by tobyj17 View Post
I haven't ordered the gears yet, but i did finally get the speedo hooked up, 30 mph off!

One thing i forgot to ask, are these gears the same with a TH350 and Th 350c?
Yes and no. The TH350C uses a driven gear that has less teeth than the TH350 may have. The TH350C is usually 17 to 25 teeth or so and the non C has more in some cases. The size of the housing will be larger for the larger (30-35 tooth- plus) driven gears, IIRC. You should be able to narrow this down doing a search on it.
07-27-2012 08:23 PM
tobyj17 I haven't ordered the gears yet, but i did finally get the speedo hooked up, 30 mph off!

One thing i forgot to ask, are these gears the same with a TH350 and Th 350c?
07-26-2012 11:47 PM
cobalt327 Talking in this thread about a TH350. But thanks just the same.
07-26-2012 11:45 PM
mmerlinn
Quote:
Originally Posted by cobalt327 View Post
The drive The driven gear always has the greater number of teeth of the two gears. Hope that helps some.
That is true for TH350s, but is not always true for other applications. Example, I know that some Toyotas use a 27 tooth drive and a 22 tooth driven as well as other similar combinations. Same with Subaru with 23 tooth drive and 19 tooth driven.
07-26-2012 03:03 AM
tobyj17 Ok, I think I got it. Thanks!
07-26-2012 12:03 AM
mmerlinn The drive gear is the gear that drives the driven gear. The driven gear is the gear that is driven by the drive gear.
07-25-2012 10:33 PM
cobalt327
Quote:
Originally Posted by tobyj17 View Post
BUT, which ones are considered the drive/driven gear?
The drive gear is mounted on the tranny output shaft. The driven gear is the one that's easily removed that is mated to the speedometer cable. The driven gear always has the greater number of teeth of the two gears. Hope that helps some.
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