3 speed rebuild
 

Who here has had their 3 speed rebuilt? I am almost finished with my 70 C10 restoration and one of the things everyone said not to touch if it isn't broke was my 3 speed transmission. After a short drive out of the shop and back in the transmission developed a pretty major leak. I assume from the input shaft. At least it's easy to remove. About what does it cost to have one rebuilt. I am not sure if it's a Muncie or a Saginaw.

Re: 3 speed rebuild
 

If the trans works good (ie No noise or grinding & doesn't jump out of gear) you do not need to o-haul it to fix a leak. If it is the input shaft you can remove the front retainer & replace the seal & gasket easily. If it is the rear seal You can pull the drive shaft & remove the seal & replace it. The side cover & rear housing gaskets can be replaced without much trouble.
George

Re: 3 speed rebuild
 

Good news! Thank you! It appears to be the input seal but I might as well do the rear seal also while I have it out of the truck. I just need to determine what transmission I have and where to get a parts kit.

Re: 3 speed rebuild
 

There is a thread on the forum about the standard transmissions.

I can't remember who started it.












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Re: 3 speed rebuild
 

Found this link below

Probably a Saginaw??

These trans only have a few differences,

I think the speedometer being on the tailhousing is the key to finding out which one it is.

Link:https://www.drivetrain.com/parts-cat...smissions-v24#

SAGINAW 1966-81 Cars, 1966-87 Light Duty Trucks:
Cast iron case and extension housing with 7-bolt side cover. Fully synchronized with 30 tooth synchro rings. 1966-69 units may have electric overdrive. It has a four step cluster and all the gears are helical cut.

MUNCIE (Heavy Duty) 1969-74 Cars, 1969-76 Trucks
Cast iron case and extension housing with 7-bolt side cover. Fully synchronized with 36 tooth synchro rings. This is the only GM 3 speed with the same bearing front and rear. This transmission is found in performance applications.









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Re: 3 speed rebuild
 

Awesome!

Re: 3 speed rebuild
 

Easy eyeball check.
Saginaw has one bolt in the top centre of the side cover, Muncie has 2 about 6 inches apart.

Re: 3 speed rebuild
 

03BlkZ
When I was searching I found this thread with a picture you took.


Link:https://67-72chevytrucks.com/vboard/...ransmission+id












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Re: 3 speed rebuild
 

So based on my picture what do you think I have? The truck is at my parents house and I won't be back to it for a few days.

Re: 3 speed rebuild
 

I have no experience with buying parts for these transmission.

I have drove trucks with those transmissions in it.

I have one parts truck with a 3 speed.

Looking back at the comments/ members have said both ways .

I don't know.

It has got me wondering which one I have?

There are 3 different numbers on the castings.

Hopefully You can nail it down with them.

The side shifter plate covers has a different bolt pattern.

Also speedometer location is different.

Hope this helps you.








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Re: 3 speed rebuild
 

I just Google some of the casting numbers from some old.pictures and it seems to be a muncie SM330. Guess I will start looking for a seal kit. THANKS!

Re: 3 speed rebuild
 

You can get seals from here.

Re: 3 speed rebuild
 

Where? I see no link.

Re: 3 speed rebuild
 

Huh!
Try this.

[url]http://www.advanced-ev.c/url]

Re: 3 speed rebuild
 

Very timely in that I just bought the rear seal and bushing for my truck with the 3 speed Saginaw. I am not sure the bushing is bad in mine but it wasn't that much more to buy it with the seal.

I've been searching online for a definitive answer but I'll ask it here. Can you remove the tailshaft housing to replace the output shaft bushing without a complete teardown?

Re: 3 speed rebuild
 

There is actually a tool that will pull the bushing without removing the tail shaft. It also requires a special bushing driver (its hollow) to clear the output shaft when driving it back in. Most transmission shops will have this tool as it works on a bunch of GM transmissions.

Most transmissions will not require a bushing replacement. Pull the seal and test fit the yolk without the seal. if you have more than about .005 radial play replace the bushing. Use no sealer on the OD of seal when you replace it. The Green or Red coating is actually a glue/sealer.

Do these transmissions even have a seal on the input shaft? I doubt it, but my memory may not be reliable.

Rick

Re: 3 speed rebuild
 

Sure they have a seal.
Here’s the link I finally figured out.


http://www.garagemotorsports.com/muncie.htm

Re: 3 speed rebuild
 

I know the Muncie 4 speed do not have a seal in the input shaft.
The Muncie 3 speeds is based on the 4 speed Muncie.
I am confident it will not have a seal. It relies on a slinger and a reverse thread to channel the oil back into the case. Part number 3, in the link you posted, is the input shaft bearing retaining nut, not a seal.

Possible the Saginaw does have an input seal. That I am not sure of as not many of these get rebuild anymore. The last 3 speed I had was replaced with a 4l60.

Some 4 speeds like the Super T10 do have input seals, I can send you a picture of that one as it is apart in the shop.

Rick

Re: 3 speed rebuild
 

On the link they post a seal for the Saginaw.