Hi All, Newbie here, 1st post. Not new to forums, just this one. Have 79 C10 here in U.K. I am a professional transmission builder who only rebuilds 50-90's American transmissions and I specialise in 700R4s. I joined this site the other day because I am rebuilding my truck and wanted information and also like to help you guys if I can.
I read this thread with some concern as I am reading some things which are simply not correct and can be misleading to the person who has the problem with his 700R4. Nobody wants to go spending money and time for nothing so I feel the need to chip in, hope not to offend anyone previously trying to help.
The 700R4's are good when they are ok (I have a performance one in my 79) but bad when they are tired and need plenty of TLC when they are repaired. They are complicated in operation and design and have weak spots. The 3rd gear clutch pack is usually the first thing to go when a rebuild is due. 90% of all that come into the shop have 3rd gear burnt up. The fault is not the actual clutch, it is weak leaky hydraulics that feed it, caused by wear and tear. They can also fail due to the TV cable being out of adjustment (more on that another time) Also more on Lock up another time. These are two areas which need a ton more clarification and I will try and write a 'sticky thread' at some point
I'll be perfectly frank with you - do not spend any money or time on this transmission. From what you have said about your problems - IT IS BURNT UP already. Nothing will cure it other than a complete rebuild. Save your pennies for this.
The way the 700 gears work is as follows - 1st is engaged mechanically already and selected by the forward clutch (Drive) 2nd is operated by the band (operated by the servo on the side) 3rd is operated by the 3rd clutch (its burnt thats why it goes to neutral, it cant hold) 4th is operated by 3rd and 2nd band together) Sometimes 4th works if it can hold the 3rd if you are cruising gently. If not there will be no 4th either because it needs 3rd. I hope that makes sense.
You cant always go by the fluid colour or smell. Sometimes the PO has already changed the fluid in an attempt to 'fix' the slipping and then decided to sell after it didnt!
I hope this information helps, probably not what you was hoping to hear but its just fact.
Cheers Jon
www.americanautomatics.co.uk
