Hello to all. I have a problem. I just purchased a 2500 GMC 4x4 SLE Suburban. I knew that the overdrive was out, now it is my time to fix. Here is whats going on. As previous posts states, 1-2,2-3 shifts are fine. That infamous fouth is good while cold, gone when warm. I notice that my rpms are way up even in third in the freeway. 50 mph at about 4000 grand in third at one point. On the retrun trip the r's were about 2200 at 60 mph. I added some Lucas Slip fix stuff to the tranny. Seemed to make it better. i noticed posts about the vavle body. Could it be a sensor? The previoud owner replaced the flywheel and stater with out removing the tranny. He said he slid it back. I was Praying that he may have broken a wire connector somewhere. A friend said it may be the overdrive pressure switch or sensor. Any and all information is GREATLY appreciated! I am mechanically savy when it comes to turning wrenches. But braindead when it comes to trannys!
Thank you in advance for your help!
Also, mileage sucks.
Blessings
Chuck Butler aka ulremember

Hello to all. I have a problem. I just purchased a 2500 GMC 4x4 SLE Suburban. I knew that the overdrive was out, now it is my time to fix. Here is whats going on. As previous posts states, 1-2,2-3 shifts are fine. That infamous fouth is good while cold, gone when warm. I notice that my rpms are way up even in third in the freeway. 50 mph at about 4000 grand in third at one point. On the retrun trip the r's were about 2200 at 60 mph. I added some Lucas Slip fix stuff to the tranny. Seemed to make it better. i noticed posts about the vavle body. Could it be a sensor? The previoud owner replaced the flywheel and stater with out removing the tranny. He said he slid it back. I was Praying that he may have broken a wire connector somewhere. A friend said it may be the overdrive pressure switch or sensor. Any and all information is GREATLY appreciated! I am mechanically savy when it comes to turning wrenches. But braindead when it comes to trannys!
Thank you in advance for your help!
Also, mileage sucks.
Blessings
Chuck Butler aka ulremember

How many miles on it?
How is the fluid and fluid level?
Has the transmission ever been serviced?
Any extra metal or clutch stuff in the filter or bottom of pan?
It needs checked out with a transmission/engine capable scanner.
Check for codes and check shift times and adptive data and slippage in all gears.
MT

Thank you MT 2500.
I will check that as soon as I can get to my buddys house. He has the Modis reader by snap on. Also, I just found out I am getting 3-4 mpg in the city. Changing O2 today.
Again, thank you with the quick reply.
Blessings to all
Chuck aka ulremember

You are welcome and.
Good luck and let us know how it goes.
MT

MT-2500. I put in some of the Lucas Slip Stop. The O/D came back. But now, sometimes it leaves. I can be going along the freeway and everything is great 2500 rpms at 65 mph. (does this sound about right for thegearing and all).Sometimes I can get on the freeway and when it comes to the O/D shift, I feel it just "slip" out if that sounds right. When U get off of the gas, I feel it engage. As soon as I give it a lil gas , it just "slips" out. If I lock baby in third rides like a thirsty champ :). Put it in O/D, same thing. Get off of the freeway, O/D is back. Any ideas what it may be? Again thank you for your replies and insight!/
Blessings
Chuck aka ulremember

Yes rpm at 2500 at 65 mph is about right.
Can you feel Lockup clutch lock in.
You will have to get it on a transmission capable scanner to see what all is going on and what the problem is.
Post back any codes.
If the Lucas additive helped it it souds like you are losing pressure on 4 th gear circuit.
The lucas thickens up oil and helps build up low pressure.
Not good for a good transmission but will help one on last leg.
Good luck
MT