Any idea what could be?

 

Yes, now I know. Your transmission has failed and needs to be rebuilt or replaced. When the RPMs go up to 3500 or 4000 and the truck is barely moving it means the transmission is destroyed.

 

ok but i know this problem was suddenly, i mean from one moment to another , the truck was running perfetly. now my questions is: is it posibliy?of break the transmision like this...
thanks everyone for your help

 

Yes, it's possible.

 

ok... so I'll have to change or rebuild the tansmission.
someboy knows a good transmission rebuild kit?

 

Depends on what transmission you have and what failed. A standard rebuild kit won't include major parts like ring gears, planetary gears or sun gears, if you have a failed or damaged one. Same goes for valve body and solenoids.

If it's the 4R70W/4R75W transmission, get the Sonnax kit to fix the common weak points:

https://www.rockauto.com/catalog/mor...nid=533&jpid=1

In addition to this you need a rebuild kit, Rock Auto carries them also. Find the most extensive one, they usually call them a "master kit" or a "deluxe kit"


But remember, rebuilding an automatic transmission is not your average DIY job, it's a very complicated task and you need to know what you're doing. It also requires a couple special tools. Take it to someone who knows how to rebuild transmissions.

 

I've used kits from Home - Transtar Industries. Make sure you have a very good manual. You can get one from Service Manuals, Owner Manuals, Wiring Diagrams, Service Bulletins - Helm Incorporated or Automatic Transmission Service Group.

 

Mark, what do you think about those Sonnax kits? Are they worth the money and do they fix "weaknesses" as they claim? I've always been recommended to get one of those if I'm getting the transmission rebuilt

 

I've never used one. I can't offer an informed opinion.

 

Sonnax is good for some things. transgo makes a good shift improver durability kit, I have one in my 4R70W. (my 4R70W hasn't been rebuilt)

 

guys i don't know what kind or number serial is my transmission. how can i know that?thanks

 

I don't know what a number serial is. What is it you want to know? Do you need to know what model transmission is in your truck?

 

I got my transmission model. It is a 4r70w. But I couldn't find any repair manual for it

 

Www.atsg.us/atsg or Service Manuals, Owner Manuals, Wiring Diagrams, Service Bulletins - Helm Incorporated both have a manual for the 4R70w.

 

The factory shop manual also has a manual for the transmission. Buy a hardcopy or a DVD on ebay, they cover everything on your car.