A Blast From the Past For those of you who remember the Slim Jim (Roto 10) years, the weld on the tube going to the fourth coupling would crack. Depending on the severity of the crack , the transmission would either slip or neutralize going into fourth gear. That was then. Today, we have a similar problem with welds cracking in General Motors 4T40-E oil feed tube assembly (Figure 1). Lube failure to the Forward Clutch Support assembly, a slipping or a loss of reverse, a loss of engine breaking in manual low, and a slipping or a loss forward are all possible with weld failure of the oil feed tube assembly. If you loose forward, you will need to be careful not to pull the unit right away. What I mean by that is being a good diagnostician, you may place a gauge on the line pressure tap only to discover that line pressure is high.  A  P0730 pending code Gear Ratio Error may be set. With line pressure being more than sufficient to apply the forward clutch, it may lead you to believe that the Input Sprag or Lo Roller Clutch is not holding. So you pull the unit only to find that they are both OK. This is upsetting when all along it was a Forward Clutch leak at the pipe weld (See Figure 2) which is accessible by dropping the bottom pan. The fluid going through the pipe to the forward clutch must first pass through a .090" orifice in the spacer plate (Figure 3). Line pressure feeding this orifice comes from the manual valve and the pressure tap for line pressure is located in the circuit before the manual valve. The feed pressure on the Tap side of the orifice via the manual valve was not affected by the pressure drop on the pipe side of the orifice. And this is why a  line pressure check could mislead you to think there is enough pressure to apply the forward clutch. A quick way to inspect for leaks at the welds in the oil feed tube assembly for forward or reverse problems is to drop the pan and filter. Then blow air into the main line tap (Figure 4) with the selector lever in Reverse and/or Drive. Air should not be heard or felt coming out of either end of the pipes where they weld to the flanges. Another blast from the past. Many thanks to Louie Zabala at WiWi's Transmissions in Miami, Florida for the Oil Feed Tube Assembly. Forward Clutch Feed Pipe Reverse Clutch Feed Pipe Lo Band Feed Pipe Forward Clutch Assembly Lube Pipe Oil Feed Tube Assembly Figure 1 Forward Clutch Feed Pipe with Broken Weld Figure 2 .090" Forward Clutch Feed Orifice Figure 3 Figure 4