Originally Posted by nostradumbass
I have a 1995 GMC Jimmy that reverse is getting soft and first gear is slow to engage. What other year GM 4L60E transmissions will fit? Or any recommendations as to what to do to solve these problems?
Put a line pressure gauge (or visit a local trans shop) on the pressure test port and go for a drive to verify proper line pressure. Base pressure at idle in P,N,OD should be around 70psi and around 140psi in R. Max line pressure should be at least 190psi at WOT in 1st or 2nd, 225psi is optimum. If base pressure is low, trans or pump is worn out. If max pressure is low, check EPC solenoid. If reverse is slow to engage, and line pressure does not come up to at least 130psi in reverse, replace the boost valve with a Transgo 0.490" boost valve (easy fix in pan).
Slow, slipping or no reverse: “lo-reverse” clutches are worn out, fluid leak in the reverse apply circuit, or (broken sunshell but you have no other issues so that should be good) . It is possible to remedy a fluid problem by removing the checkball from its cage in the case in the rear of the trans may help (must remove valvebody), or adding a high-viscosity additive such as Lucas Transmission additive or other seal restorer product. I am leaning towards a worn boost valve (can replace in the pan).
If you also notice Soft shifting, gradual performance degradation. 1. Poor line pressure rise due to leaking boost valve, 2. clogged EPC filter screen / failing EPC solenoid, 3. or worst case a leaky internal seals throughout the transmission. Transgo HD2-C kit fixes first two without removing trans. Seal restorer may fix last problem, but probably R&R if there is lots of clutch and bearing found in the transmission oil filter and bottom of the pan. Also try a transmission flush with BG brand products (Firestone stocks it) before servicing the transmission for about 50 miles.
Believe the years are going to be 1993 to 1996, but your going to have to make sure the transmission has the right boost valve and servos in the internal works of the transmission.
The 4L60E is also used in the 2.2 liter engine and was tuned to be softer in shifts then the ones for the V6 and V8s.