F 350 4WD Pickup V8-6.9L DSL (1983)
Vacuum Regulator Valve: All Technical Service Bulletins
A/T - C6 Harsh/Delayed Upshifts
Article No. 84-16-31
TRANSMISSION - AUTOMATIC - C6 - (6.9L DIESEL) - DELAYED AND HARSH UPSHIFTS IN DRIVE MODE
LIGHT TRUCKS 1983-84 F & E SERIES
Harsh and delayed upshifts in the drive mode, at light or moderate throttle may be due to the engine not having been completely broken-in. Some new
engines can have high internal friction, requiring slightly larger throttle opening to attain road speed, which results in later and harsh transmission
upshifts. This condition is considered normal for up to approximately the first 3,000 miles, and the Vacuum Regulator Valve (VRV) setting should not
be re-adjusted.
The Vacuum Regulator Valve (VRV) controls transmission shifting by modulating the vacuum signal to the transmission. The VRV uses throttle
rotation/position to sense engine load (rather than intake manifold vacuum which gasoline engines use). If engine internal friction is high, the
transmission will "think" it is seeing a higher road load than actual; and, therefore, upshifts will be delayed and may feel harsh.
Prior to 3,000 miles, technicians should not adjust the VRV to change shift feel. Any altering of the vacuum setting (VRV adjustment) will cause
eventual transmission failure under moderate or heavy load (as the engine breaks-in and internal friction reduces, shift points will occur too early, with
excessive slip at shift points).
Should the harsh and delayed upshift continue beyond the 3,000 mile break-in period, refer to the 1984 Truck Shop Manual, Section 17-10 for VRV
adjustment and/or diagnostic procedures as required. If condition is still not resolved, call Ford Motor Company, Transmission and Chassis Division,
Field Evaluation Section, for assistance - 1-(800)-521-5005.
OTHER APPLICABLE ARTICLES: None
WARRANTY STATUS: "INFORMATION ONLY
