To the untrained eye, nearly all GM automatic transmissions look the same. They are all made out of aluminum (with the exception of the very early Powerglide), they have the same bellhousing bolt patterns, and they have very similar case designs. There are some things that you can do to make sure that you are properly identifying the 700R4. It’ll look most similar to the 2004R at first glance. If you need to start from scratch, try this old article from Hot Rod.
If you find a 4L60, you’ve found a late 700R4. They are the exact same transmission. However, the 4L60E is physically similar, but not easily substituted for it’s earlier counterpart. If you see the term MD8 stamped on the passenger side of the case, right by the bellhousing.
700R4 Identification- The Easy Way
The easiest way to identify a 700R4 underneath of the car is to look at the bolts. If you have a clear view of the transmission count the bolts. Did you count 16? If you did you have found a 700R4 or a 4L60. Remember, 4L60 was just another moniker for GM’s popular overdrive. You want to make sure that you don’t have a 4L60E on your hands though. In most cases if someone has told you that you are looking at a 700R4 and you count 16 bolts you can be reasonably sure that you have found what you were looking for. But to be sure check to see if the long “TV-Cable” is attached to the Transmission. If there is none look at the tail shaft. If the speedometer cable is mechanical than you have a 700R4. If it has wiring coming from it you are looking at a 4L60E. Sometimes when people don’t really know what they are looking for, they will search for MD8 transmission. MD8 is stamped on the passenger side of most 700R4 cases.
700R4 Identification- With the Identification Tag:
Lets say that you have found a transmission at a swap meet, on Craigslist, or at the salvage yard. Many people want to know exactly what year the transmission came from, and what vehicle it was in.
The first digit of the Identification Tag will be the model number. It is not intuitive. The first units were for the 1982 model year. So you would expect the first model year ID number to be either 2(for 82) or 1, right? It’s not. It starts with a 9 and then jumps to 3.
The model years are as follows:
|9=1989 or 1982|
- The second group of digits is the Model indicator. It’s two letters.
- After the model the next area of the tag is the transmission type. It is one letter. In this case M is letter code for 700R4. 82-85 are missing this entirely. Try using the method above to figure it out.
- The fourth area is the plant that the transmission was manufactured in. It is one letter
- The fifth line in the code is the serial number of the transmission. If the serial number is ground off it’s likely that it was rebuilt by GM at some point.
- The sixth line is the date of manufacture.
- The seventh line is the shift in which the 700R4 was built.
There was a 700R4 with a thicker case built for 4×4 trucks. It is known as the “K case” version because of the rather large K stamped on the bellhousing area. This is certainly the easiest way to identify it. It was made exclusively for four wheel drive vehicles. They are commonly found on on 80’s 4×4 pickup trucks. They are very desirable in the off road community. This forum has good info on K cases.
As a footnote here, if you are going to buy a rebuilt unit from a reputable transmission shop, or an aftermarket supplier such as TCI it really should not matter what year it originally came from, as it will be totally gutted and rebuilt with the much stronger components. You should be able to find a reasonable one for around $700 that should handle at least 400 horsepower. It would certainly be in your best interest to ask what components were replaced. Many people feel that the input drum is the point of weakness for the 700R4.
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