700R4 Identification Issues- Anybody help?

[Trump]

Hopefully somebody can help separate the identities and help me out. I am doing a 700R4 trans swap in my '64 C10. I picked up this trans because it was advertised as being out of a 1991 Chevy van and was mated to a later style 1pc rear main SBC (saw for myself). Figured chances were good that seller was telling the truth. Now thinking that the engine and trans may have been earlier (1986) and swapped into the later model van. Regardless, I still have some questions about the trans.

So here's my deal. I have been reading all the posts on how to ID 700R4 transmissions and which ones are desirable and this and that. Unfortunately, there seems to be gaps at least in regards to getting a clear answer on the one I have.

I have been using these posts for reference (amongst others):
http://www.camaros.net/forums/showthread.php?t=157368
http://www.thirdgen.org/techboard/tr...4-year-id.html
http://www.hotrodders.com/articles/T...ification.html

Some say 1986 and on are good, some say 1987 and on are good. All say that the MDB or K case are the most desirable, however disagree on what year the MDB case started. I have seen the Year codes. (However I am still interested in finding a listing of Model codes) and get the Julian date.

All that said. Here is my info:
Stamped number on passenger side rear above pan: 6YKM256H
-Mine also has the "MDB" cast into the case on the passenger side bellhousing (although smaller than others I have seen).
-My valve body appears to be the later version and has a switch for 4/3.
-Tailshaft casting#: 8642547-5
-"14" cast into side of case above TV cable area on both sides of case
-Had the hall effect speedo sender with the metal "reluctor" wheel/gear

So, from what I have read, mine should be a 1986 (possible if van when through drivetrain transplant, I suppose). I have read that the MD8 casting didn't start showing up till 1988? If so, than what is it doing on a 1986 case?


I am not sure how many splines the input shaft has yet (27 or 30) but intend to check this evening. I also noticed that there is another number stamped on a pad on the passenger side of the trans at the bellhousing where it mounts to the engine block ( I have not yet gotten that number). Anybody know what that number relates to? Likewise, I have not looked for a pump serial number. But I will check all this this evening and post my findings.

I am already committed to it and have installed a TCI lock up kit amongst other things. So I will be using it. Just curious to know more about it.

It just seems like kind of an in betweener in regards to information posted on the net and was wondering if anybody had some hard solid facts on it and maybe what the Model code decodes to to see if it actually was a transplant.



I have included some pictures for reference. Thanks for any input in advance.

[luvbowties]

I cannot answer lots of your ???, but may be able to help a bit. As far as desirable trannies, I've learned you can't be far wrong as long as the case has the rainbow running thru the top coolant line...see picture. (Rainbow has to do with extra cavity for cooling.) Also, I have read enough to know that desirable units are from somewhere in mid-year 1987 and up--NOT 1986!
HTH,

Sam

[Trump]

I have heard about the casting line before but never seen a picture. It's helpful. Thanks.

I would imagine that the discrepancies between the 1986-1987 years that I keep seeing is probably related to model year of the vehicle versus manufacture year/date of the transmission. One would guess that at some point in 1986 they had to transition into manufacturing the newer style trans for the '87 model year.... maybe? Or maybe they truly didn't start manufacture of the newer version until 1987 and some 1986 manufactured trans crept into the '87 line-up? Of course this last guess would line up with your last statement. Which makes sense.

In hind sight, I should have checked the date code on the engine it was mated to to see if they came from the factory that way. I suppose there is a chance that it was a replacement or rebuilt trans from a trans shop that was installed later into the van. The TC actually had paint pen on it from a local trans shop here in town and it was clear that the TC was either new or a remanufactured unit. The date on the TC was less than a year ago. The case was pretty clean for the most part when I got it as well, so that might hint that this could have been the case....

The mystery continues.

[Chevy Fleetside]

I have the ATSG Update handbook and it says that is a 1986 "B"-CAR (wagon). This is how it is writen in the book.

[Chevy Fleetside]

You can also count the splines. Early model has 27 and later has 30 I believe.

[Trump]

Originally Posted by Chevy Fleetside

I have the ATSG Update handbook and it says that is a 1986 "B"-CAR (wagon). This is how it is writen in the book.

Thank you. Solidifies what I expected a bit.

[NEWFISHER]

I have always run 87 and up MD8 cased 700r4's with no problems. You DO NOT want an 83-86 non updated case style!

[ls60apache]

agree its a 86 model trans the 6 in the number above pan lip is the year. plus you should have a 30 spline input shaft also starting in 87 was an auxiliary valve body,that would be installed where u see the plate with the 4 bolts on 86 back.