HELP! Need Transmission and Valve Body ID

[Corellian Corvette]

Hey everyone! My transmission builder is having trouble diagosing a problem - he's rebuilt the unit twice, and both times we get no reverse gear. He's build a lot of trannys and is stumped.

We fear the problem may be a mis-match in parts. He's using parts from two cases and I'm trying to ID the parts and see if that's the problem.

Here are the numbers on the case that he's using

754-4 (large Stamp)
PK2892090L 2764 8271 (Stamp on drivers side by the pan)
2892754-4 (Dr. side case stamp)

Here's the Valve Body ID
3743158

Here's the case he took the valve body from
433-8
PK3496939L 3301 9048
07-3-410433-8

If anyone can help that would be great. Thanks!

[RD]

has he made sure that the rear servo piston is being engaged?  he can test it by applying some low pressure air into a port next to the accumulator.  If the rear servo piston doesnt move, that means that the seal is bad. (see pic)



though the 71 and 69 model year valve bodies do have some differences, this should not affect your the reverse band from engaging.  Do you have 1st?  Reverse and first work off the same band.  If you have first, then its a valve body issue and he should recheck the valve body if he tore it apart and rebuilt it.  I dont have my manual with me right now (its in the garage and its 9 degrees outside) so I can check on it tomorrow. Hopefully John can chime in on this.

[Corellian Corvette]

RD thanks I will ask him about the rear servo piston.

The problem is very perpexing. I DO have 1st gear and 2nd Gear, but NO 3rd gear and NO reverse. The bands aren't burning, there is some light burning on the clutches (this is after only a few minutes of testing). He's never seen this problem before. Any help is appreciated.

Do you happen to know how to decode what parts I have? Thanks again VERY much!

[RD]

If he hooks up a pressure gauge to the rear servo, it should be showing in between 230-260 psi at the rear servo (there is a plug he can remove on the outside to hook up his pressure gauge). 1st gear should have 55 psi at the rear servo.

The fact that you dont have direct drive (3rd) or reverse tells me that there is something wrong with the valve body OR your front clutch piston is not engaging.  I.E. the piston in the front clutch drum has a bad seal so as to not engage the clutch discs.  Direct and Reverse both use the front clutch drum.  If you dont have either of those gears, that is the first place i would look.  Replace the front clutch drum piston seals and go from there.  There are two.. a inner seal and an outer seal.  Since your clutches look somewhat burned.. they could be doing a lot of slipping going on due to inappropriate engagement of the front clutch piston due to bad seals (think of blowby of fluid in the piston so as to not engage the piston fully).

As far as decoding the two transmission components...

PK2892090L 2764 8271 (Stamp on drivers side by the pan)

came out of a 69 383 2bbl


PK3496939L 3301 9048

came out of a 71 383 dodge pickup d100 or d200

[John_Kunkel]

This is the danger of mixing parts from different years.

Since the problem is rooted in the front clutch it's possible that he used the '71 drum on the '69 reaction shaft support or vice versa. There is a difference in the drum bushing width between these years and also a difference in the sealing rings and the spacing between the rings. In rare cases the sealing rings can block the feed port in the drum or allow leakage at the drum.

Did the builder perform an air check after assembly? Probably not, an air check would find problems like this while still on the bench.

[Corellian Corvette]

Thanks RD/John I will give him this feedback and ask. He said he air tested things, but I will check again.

Any ID on the Valve Body? Could this be a problem? (in terms of using a later or incorrect Valve Body?)

That valve body came from the 71 383 BB, and it's being used in the case from the 69 383 2bbl.

Thanks again!