TH700R4 SLIPPING 4TH GEAR

[nokia]

Hi everyone . I have a problem with my Silverado 350 c1500. the TH700R4 transmission only started slipping in 4th gear all of a sudden. the others gears work fine as always. I've read that if the other gears don't slip it means it's not a problem with worn friction discs. Has this happened to any of you? THANKS

 

[Supercharged111]

Whatever you read was wrong. How hard is it to find someone in Italy to go through that trans? If I had to guess, I'd say the 3-4 clutch pack is done. You'll know for sure if it's that or the band when 2nd or 3rd follows suit.

 

[NickTransmissions]

Hi everyone . I have a problem with my Silverado 350 c1500. the TH700R4 transmission only started slipping in 4th gear all of a sudden. the others gears work fine as always. I've read that if the other gears don't slip it means it's not a problem with worn friction discs. Has this happened to any of you? THANKS

You can check for an excessively worn 4th apply servo piston scarf cut sealing ring with compressed air with the pan off. First, check servo travel - should not exceed 1/8 of an inch inboard. If it checks out, drop the pan and look for the small hole on the pan rail of the case, just below the servo cover and put air into it. Watch for firm band apply. If the apply is weak, you hear air hissing from the servo, remove the servo cover and piston and replace the seal.

As mentioned above, slipping in 4th is usually 3/4 pack failing, the above servo and apply trouble shooting assumes you dont have any black clutch material or other debris/metal and fluid smells good (ie not burnt) and is still normal looking red.

Otherwise, if you see black clutch material or any other debris, put the pan back on with a few bolts, yank it out and overhaul it.

 

[nokia]

the fluid on the dipstick is clear, is it this video about the components and the test you said :

"GM Automatic Transmission 2-4 Servo Install-Rebuild Video" ?​

 

[NickTransmissions]

the fluid on the dipstick is clear, is it this video about the components and the test you said :

"GM Automatic Transmission 2-4 Servo Install-Rebuild Video" ?​

Please quote or mention me if you'd like me to respond so I know you have replied.

Here's my video showing the Servo installation - skip to 2:40 for the servo portion. Here are instructions from Sonnax for checking servo travel - skip to page 2.

It's possible but not likely that the servo is the only problem but it's worth checking to positively rule it out.

 

[nokia]

Thanks Nick.You were very clear and kind.My truck has 160,000 miles and may need a full rebuild. I'm a mechanic but I've never worked on automatic transmissions.I would like to try to rebuild but I'm a bit afraid of making a mess. In my area in Italy there are transmission specialists but not for American automatic transmissions. I will let you know. Thanks again.

 

[NickTransmissions]

Thanks Nick.You were very clear and kind.My truck has 160,000 miles and may need a full rebuild. I'm a mechanic but I've never worked on automatic transmissions.I would like to try to rebuild but I'm a bit afraid of making a mess. In my area in Italy there are transmission specialists but not for American automatic transmissions. I will let you know. Thanks again.

You're welcome...If you have built engines or rear ends in the past, you can build transmissions as both of those other things pose greater cost and risk...If you follow my and other reputable YT channels' vids, acquire the ATSG manual and ensure you can obtain everything you need, you should be fine...It may be worth it to grab a junkyard core for like $100 and tear it down for parts and so you can familiarize yourself with the unit before tackling your own...

 

[nokia]

I started following your channel.. it's very very very interesting. I continue to use my truck (it only slides if I push full throttle fast) and if it falls over or goes bad, I will get a rebuild kit and try to restore it. Your suggestion gave me courage. I have to familiarize with my trasmission.. here we don't find a bad trasmission in the junkiard . thanks againg .. we stay tune