Engine/Transmission (1998.5 - 2002) loss of boost in overdrive

[STEVALLA]

This has probably been covered before but I notice that I can not get over 14-15 lbs boost in OD even at WOT around 2k rpm. Get 19 psi at same readings in other gears, 2k rpm, 1k egt, no drop in fuel pressure. Does over drive electronically somehow limit boost pressure to 14-15 psi? Do I have a problem? p. s. occurs hauling flatbed trailer,wt loaded was around 10k lbs total trailer wt. Truck runs ok pulls well, just curious about lower boost in OD.



Surely, others have noticed this behavior. There must be many

early 24 valves out there with automatics, someone must have noticed this.

 

[lmills]

I beleive there is a TSB about a cut back in power in OD to protect the transmission. You can have it corrected so it doesn't cut back. I am not sure if it will void your warranty, but figure will





update: I found theTSB I was thinking of. It is #18-024-00. As far as I know it only covers trucks with build dates from 12/99-11/00. Sorry, I guess that does not include you.

 

[LSMITH]

The 98 and 99 were not de-rated in OD, most of the 00's were exempt from this as well.



Not sure what could be causing this unless you are pulling at low RPM. When stock mine would not make over about 14-15 PSI under about 1600 RPM, at 1900 or so it was up to 18 PSI. If anything you should see about a pound or two higher in OD as the load on the engine is greater.

 

[pwr2tow]

stevealla,

Mine will do the same as yours when loaded with whats in my signature until I have to put more power to it to pull hills then the boost will come up no matter if I'am in OD or third direct. I thought it was strange at first too but I get better fuel mileage in OD at lower boost than I do at higher boost level in third direct at the same speeds, I guess the mileage and boost levels would be correct for fuel mileage reading better in OD.



Ron