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-   -   T-400 speedometer gear question (http://www.hotrodders.com/forum/t-400-speedometer-gear-question-235327.html)

sqeezeit 07-26-2013 09:05 PM

T-400 speedometer gear question
 
Are the speedo drive gears all the same physical size?I ask because I have a smaller tooth gear housing and the speedo gear doesnt even make contact with the drive gear on the output shaft?Someone told me that I might need the 40-45 tooth housing because it offsets the gear more to make contact?I am just wondering if its not something with the drive gear being wrong also.Any one have any ideas.I guess I hate to buy new housing and still not work.

cobalt327 07-27-2013 04:38 AM

Quote:

Originally Posted by sqeezeit (Post 1698339)
Are the speedo drive gears all the same physical size?I ask because I have a smaller tooth gear housing and the speedo gear doesnt even make contact with the drive gear on the output shaft?Someone told me that I might need the 40-45 tooth housing because it offsets the gear more to make contact?I am just wondering if its not something with the drive gear being wrong also.Any one have any ideas.I guess I hate to buy new housing and still not work.

There are both large and small gear sets.

More here.

sqeezeit 07-27-2013 06:32 AM

Thanks but not sure that helped,Ive seen that page and says nothing(unless I missed it) about different size drive gears(not tooth count).Iam wondering if something came loose on the install,because my drive gear on tail shaft is towards the engine to far,maybe it slid out of place on the shaft?

Crosley 07-27-2013 07:03 AM

The T-400 speed-O housings are divided into 36-39 and the 40-43 tooth designs.

The T-400 stem of the plastic gear is a different diameter for each housing tooth count design. You can not interchange the gears between housings. A 44 tooth gear will not fit a T-400 housing for 36-39 tooth gear or the other way around.

I suggest you verify the correct parts are on the T-400 output shaft, then verify the driven gear and housing. I had a fellow a few years ago , trying to install speed-O housing for a torque flight into a T-400.

cobalt327 07-27-2013 09:32 AM

Quote:

Originally Posted by sqeezeit (Post 1698447)
Thanks but not sure that helped,Ive seen that page and says nothing(unless I missed it) about different size drive gears(not tooth count).Iam wondering if something came loose on the install,because my drive gear on tail shaft is towards the engine to far,maybe it slid out of place on the shaft?

The drive gear should be basically directly under the driven gear housing hole in the tail housing.

If you have a plastic drive gear, there's a spring steel clip that has one end secured in a hole in the tailshaft. The other end snaps the drive gear into place. There's a chance the drive gear was knocked out of position, or the wrong size clip was used instead of the correct clip.

Steel gears used on some early transmissions are a press fit and I seriously doubt you'd be able to move one out of position under ordinary circumstances, so if there's a steel gear and it's loose enough to be bumped out of position you need to replace it altogether.

zooma 07-27-2013 12:19 PM

Info Link for your speedo issues
 
Try this site for some additional info on T-400 driven and drive gear set ups
AOD, AOD Performance Transmissions from PATC, AOD Transmission, AOD Mustang, AOD

zooma 07-27-2013 12:23 PM

I think this site will get you to the speedometer side of there business
transmission center.org

mmerlinn 07-28-2013 01:00 AM

Quote:

Originally Posted by sqeezeit (Post 1698339)
Are the speedo drive gears all the same physical size?I ask because I have a smaller tooth gear housing and the speedo gear doesnt even make contact with the drive gear on the output shaft?Someone told me that I might need the 40-45 tooth housing because it offsets the gear more to make contact?I am just wondering if its not something with the drive gear being wrong also.Any one have any ideas.I guess I hate to buy new housing and still not work.

As noted by several before me, you cannot mix and match speedo gears and housings. The gears (40 & up) with larger tooth counts are larger in diameter than the smaller gears (39 & under) to accommodate the extra teeth. The larger diameter requires a different offset so the teeth make proper contact with the drive gear.

If your gear and housing match, then you have a different problem, possibly, as noted above, a missing or loose drive gear.

What is confusing to me here is that you say you have the smaller housing (39 & under I presume), yet your gear does not contact the other gear. If you had a mismatched housing and gear in this instance, you could not even insert the assembly into the transmission without using a bigger hammer and ruining the gear(s) in the process.

How about counting the teeth on the driven gear and posting the tooth count and the casting number(s) on your housing? There may be something else at play here that is not obvious without more info.

sqeezeit 07-28-2013 01:42 AM

Quote:

Originally Posted by Crosley (Post 1698457)
The T-400 speed-O housings are divided into 36-39 and the 40-43 tooth designs.

The T-400 stem of the plastic gear is a different diameter for each housing tooth count design. You can not interchange the gears between housings. A 44 tooth gear will not fit a T-400 housing for 36-39 tooth gear or the other way around.

I suggest you verify the correct parts are on the T-400 output shaft, then verify the driven gear and housing. I had a fellow a few years ago , trying to install speed-O housing for a torque flight into a T-400.

Yes this is exactly what Iam trying to do, what u last said in message

sqeezeit 07-28-2013 01:50 AM

Quote:

Originally Posted by mmerlinn (Post 1698707)
As noted by several before me, you cannot mix and match speedo gears and housings. The gears (40 & up) with larger tooth counts are larger in diameter than the smaller gears (39 & under) to accommodate the extra teeth. The larger diameter requires a different offset so the teeth make proper contact with the drive gear.

If your gear and housing match, then you have a different problem, possibly, as noted above, a missing or loose drive gear.

What is confusing to me here is that you say you have the smaller housing (39 & under I presume), yet your gear does not contact the other gear. If you had a mismatched housing and gear in this instance, you could not even insert the assembly into the transmission without using a bigger hammer and ruining the gear(s) in the process.

How about counting the teeth on the driven gear and posting the tooth count and the casting number(s) on your housing? There may be something else at play here that is not obvious without more info.

I never did count drive gear teeth yet,and I think it was yellow in color,not sure.I do have the right housing and driven gear,it is a 36-39 housing.I know the 40 and up are bigger diameter of driven gear so wont fit my housing(tried it before I knew this).Will get back with more info,but just wondering if the drive gears are different diameters also?Could it not have the right drive gear,from what I read theres a few different tooth count drive gears but I guess didnt or wouldnt think it wouldnt even touch the speedo/driven gear if it was wrong,I dont know.

Crosley 07-28-2013 11:15 AM

Photos of T-400 output shafts. I have these parts on hand. I dont need to search the web for photo stuff that may be correct or not. :D .. hope this helps

T-400 both shafts:

http://www.hotrodders.com/gallery/da..._speedo-02.jpg


T-400 metal gear:

http://www.hotrodders.com/gallery/da..._speedo-03.jpg


T-400 Plastic gear with clip:

http://www.hotrodders.com/gallery/da..._speedo-04.jpg

cobalt327 07-28-2013 08:29 PM

------------

zooma 07-29-2013 05:56 AM

Tooth Count and Housings
 
Not sure if you got the answers your looking for yet. The drive gears on your Output shaft can be either 14 or 15 tooth counts. The plastic one is a 15 tooth gear, the metal one looks a lot smaller and could be incorrect. You will need to trace one tooth on the gear from beginning to end, then count the remaining teeth to determine the count. 400 driven gear housings will work with any drive gear, they range from 34-39 and 40-45. To determine what you need go to transmission center.org to use their speedometer gear calculator.

sqeezeit 07-29-2013 06:57 AM

Thanks for everyone's input very much apreciate it I know I have smaller housing with the right size smaller tooth count driven gear just don't know why it doesn't make contact with the drive gear on tail shaft? When I get home in a couple days will look a little closer and update status. Thanks again

sqeezeit 07-31-2013 01:27 PM

Ok guys, update on issue.i found out I'm my own worse enemy of stupidity!after further looking it seems there is no speedo gear on the tail shaft.lol


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