possible ABS problem ??

[Bobby A]

Its me again guys, just a different topic, new issue.
This is an intermittent problem. Just yesterday I was backing up the truck and it seemed like it was bucking, so I took it for a low speed drive around the park and did a number of start and stops and backing up and stop. It is hard to described, but its almost like when you apply the brakes kinda hard and the ABS kicks in. Kinda like that. At first I thought it was a trans issue but I took the truck to a very respectful trans shop and they put some kind of computer on the truck and took it for a drive and they said they could not get the truck to do what I told them and there was no codes coming up and the trans is in good shape. Anyone know what I'm talking about and maybe has had this happen to them and what the fix is ?? Thank you guys very much
Bobby A

 

[jghflys]

If the pedal is pulsing it is probably ABS. If not, could be a warped rotor. Some have had problems with the ABS sensor mounted at the top of the rear differential.

 

[Bobby A]

If the pedal is pulsing it is probably ABS. If not, could be a warped rotor. Some have had problems with the ABS sensor mounted at the top of the rear differential.

Thank you for that information,

 

[Ozymandias]

Probably warped rotor, like said.
Check if the frequency changes with speed.

 

[Bobby A]

Probably warped rotor, like said.
Check if the frequency changes with speed.

Will do, I will report back in the next couple days, thanks very much

 

[Bobby A]

Followup,
I drove the truck yesterday about 50 miles. I did a test to see if it was the rotors going bad or warped and no pulsating in the pedal upon stopping. And of course I could not get the truck to do what I first experienced.

 

[Jim W]

On my truck when I had an issue with the ABS, I had an idiot light pop up on my dash and no DTC be stored in the ECM. I thought that this too was from the rear axle ABS sensor. As everyone was pointing to this as being an issue. I tried to diagnosis this problem to, but I could never duplicate the issue and my testing never showed an issue with the sensor.

For me it turned out to be a front wheel BRG hub that was going bad. When I had both front hubs replaced the ABS problem went away.

Now are you seeing an ABS light Illumining on your dash? Do you have a code reader to see if there are any fault codes?

Now for a SWAG!

Do you have a 68RFE auto transmission? When this occurred is the transmission oil cold?

If you have a 68RFE transmission, and the solenoid control valve is original. There may be an issue with this control valve shifting using cold oil. The truck will buck and seem to be having a brake issue. Once the oil warms up the issue will go away, and the truck will shift normal. I do not believe any codes will be thrown when this occurs and is very
random in occurring and is hard to duplicated.

I believe SAG2 (a member on this site) may be able to shed some more light on the control valve issue, that the early 68RFE's had.

 

[Bobby A]

Jim W
No codes or cel coming on, I had a trans guys put a scan on and drive it. He said the trans is running normal. As you said, it seems to happen when the fluids are cold. Not sure what trans is in it but probably the 68RFE if that was a standard back in 07 it is the 6 speed trans, not sure if that helps identify. My issue sounds almost identical to what your was. Thanks for that info, I am getting ready to drive about 1400 miles and 200 of them is pulling a heavy 5th wheel. I am leaving on Tuesday morning. Not sure what I should do if any, because I take it to a shop and the fluids are hot. Not sure what BRG means ??

 

[Jim W]

Bobby, BRG, is an abbreviation for bearing.

Now I believe the solenoid valve will not throw a fault code . So, the transmission shop will not fine any trouble codes with the data recorder when attached. Nor any control issues

I would do a search on this site for any 68RFE transmission issues you might find what was discussed about the control valve.

Good luck and keep us informed about your transmission.

 

[Bobby A]

Jim W,
Thank you for the GREAT information, I will post back when I can. BTW, I had all the fluid changed by the dealership about 2 month ago, drove the truck with 5th wheel attached close to 1000 miles with no issues other than a CEL described on my very first post to this forum. This CEL had nothing to do with my current issue on this post.
Thanks so much,