Dismiss Notice

Welcome To CK5!

Registering is free and easy! Hope to see you on the forums soon.

Score a FREE t-shirt and membership sticker when you sign up for a Premium Membership and choose the recurring plan.

TH400 Help, Wierd Stuff

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by mnstr_fx, Jan 23, 2002.

  1. mnstr_fx

    mnstr_fx Registered Member

    Joined:
    Sep 13, 2001
    Posts:
    78
    Likes Received:
    0
    Location:
    IL
    I recently installed my rebuilt TH400 into my 77'. The rebuild was due to I did not know what was in it and I wanted to add a TCI shift kit. During the rebuild I had an extra set of Intermediate / Direct / Forward Clutches which came out of a "racing" transmission. I looked over all components very carefully and noted the only differences were with the Intermediate clutch assembly. (Note: I replaced ALL piston seals and air checked the clutches during the rebuild). The main difference being an extra intermediate drain back hole which was added when the guy upgraded to the 32 element sprag. BTW that was the real reason that I threw it in :-)

    Well, I have been driving the truck and noticed two things. 1) All of the fluid seems to drain back into the pan after I shut off the engine. 2) I seem to have to "burp" 2nd gear, (i.e. the Intermediate Clutch), after I first start out in the morning.

    The fluid level thing bugs me a because I have rebuilt 3 other TH400's and never had a problem like this. Warm, this tranny shows the level where it should be, but after I shut off the engine, the dip stick shows about 1 1/2 to 2" more fluid. This places it way up into the dip stick tube.

    The other problem gets even wierder after I started to play with it. I have noticed that if I start out cold, hold out 1st gear until ~2500 RPM, then shift into 2nd gear, there is no slipping / burping going on. It just bangs the gear and away we go. After this, the transmission seems to work o.k. No more slipping when shifting into 2nd gear. BTW the rest of the gears, (1st, Reverse, & 3rd) are always rock solid.

    Any thoughts as to either of these things. I am wondering if the fluid level and "burping" are connected or if there is some check valve that I forgot to put in. For the life of me I can not remember anything that I did wrong with this tranny. All ideas are WELCOME.

    76-82 Chevy Pickup / Blazer - K5-K10-K30
    90' TBI
    TH 400
    203 / 205 Doubler
    Dana 60, Corp 14 - 4.88'd - Detroit Locked
     
  2. dyeager535

    dyeager535 1 ton status Premium Member

    Joined:
    Dec 13, 2000
    Posts:
    26,979
    Likes Received:
    189
    Location:
    Roy WA
    Sounds to me like they are connected. Obviously its typical for fluid level to rise when the engine is off, but not as high as you say....I don't think mine goes higher than about 1/2 quart over the "full hot" mark.

    I can't help you anymore than thinking the problems are related though, it sounds as if fluid just isn't making it somewhere, hence the "burping" you have to do...sounds to me like something is dry when it should be coated or full of Dexron...

    Dorian
    My tech/links page: <a target="_blank" href=http://www.dorianyeager.com/index2.html>www.dorianyeager.com/index2.html</a>
    Why insist on counting when the ring gear has the tooth counts stamped in?
     
  3. mnstr_fx

    mnstr_fx Registered Member

    Joined:
    Sep 13, 2001
    Posts:
    78
    Likes Received:
    0
    Location:
    IL
    I understand what you mean, but I am curious as to what was either left out or what is allowing it to leak down so much. It is hard for me to understand that the extra drain back hole in the intermediate clutch could allow so much fluid to drain back into the pan. I guess it is connected to the direct clutch.?.? Maybe when it drains both of the clutch packs are draining. Either way, I don't think that this is easily fixed or does it need to be fixed.

    Does anyone else run a TCI shift kit in their TH400 trannys???? If so, does it act wierd?

    76-82 Chevy Pickup / Blazer - K5-K10-K30
    90' TBI
    TH 400
    203 / 205 Doubler
    Dana 60, Corp 14 - 4.88'd - Detroit Locked
     

Share This Page