[Bobkat]

How can I tell what year a 700R4 transmission is. I have an 84 and it has gone to crap twice on me. I am told that I need an 87 as the early ones were problematic. So once again how do I tell that it is an 87, serial numbers or what?

Thanks

 

[scholman]

count the splines on the input shaft.....weak trans has 27 splines
stronger has 30 splines. Corvette and IROC transmissions also have better oiling so if you rebuild the 30 spline 700r4 put in the better internal parts for a very strong trans.

Scholman

 

[mmerlinn]

Tag numbers will tell you the year. So will the production codes on the pan rail.

 

[Bobkat]

This is all I see for ID on this transmission unless I missed something.

1. The number "3" on the right side above the TV cable location
2. The letter "K" on the right side of the bellhousing area
3. "MD8" on the right side bellhousing about 5" below the letter "K"
4. The same letter "K" on the left side bellhousing
5. The same number "3" on the left side of the tranny
6. The plate inside the bellhousing that holds the seal for the torque converter has "8654303" on it.

 

[mmerlinn]

None of those numbers mean anything for identification purposes as all of them are casting numbers, some of which (like MD8) apply to all 700 transmissions. The only numbers that would matter would be those applied AFTER the transmission was built in the factory. All of the numbers you give would have been applied before final assembly, sometimes months or years before.

There should be a paper or plastic laminated tag glued to the top of the bell housing. Some of the numbers on it would tell the year. Production codes stamped into the pan rail will also tell us. Numbers stamped anywhere else are meaningless for this purpose.

 

[Bobkat]

splines

being that I am a novice at automatics I counted the splines on the output shaft. The longer of the two shafts on the front. 30 splines on the long shaft. The shorter shaft has 27 splines. The longer shaft must be the output shaft.

 

[mmerlinn]

being that I am a novice at automatics I counted the splines on the output shaft. The longer of the two shafts on the front. 30 splines on the long shaft. The shorter shaft has 27 splines. The longer shaft must be the output shaft.

The output shaft is at the opposite end of the transmission from the input shaft. All 700s have output shaft with 27 splines, same as 350s, 4L60s, some 400s, and a few other automatics.

Input shaft counts are all over the board with 700s having either 27 or 30 splines. Just counting the input splines is not enough as some 700s had 27 splines from beginning to end of production. The only 700s that did not have 27 splines were the V8s (and the 6 cylinders using a V8 case) from mid-84 to end of production. All others always had 27 splines.

 

[Bobkat]

yes, I made a big error in my last post. Input shaft is at the front. It has a smaller longer shaft with 30 splines. There is an outter shorter larger od shaft which the smaller longer shaft comes through (center) which I do not know what it is for. It has 27 splines. Both are at the front (input) of the transmission. I looked for a tag on top but unfortunatley the only thing left is adhesive with nothing legible. The person who has the transmission told me that it came out of a 1987 chevy PU but that doesn't mean much as any number of transmissions could have seen service in the truck. So without any diffenitive way to I.D. the transmission then I should pass and wait for one that I am certain is a 1987.

 

[mmerlinn]

The unknown 'shaft' in the front is the stator support for the stator inside of the converter.

 

[Bobkat]

OK, suggested that I find the number on the pan rail. here is what I found. 7TXM085A
Now I am told that my 84 was a bad year and 87 was what I need, is this correct? It is going in an 84 c20

 

[mmerlinn]

That is an 87, so you have what you are looking for.