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GM Tech (Cam)
GM Tech (Cam), Buick Technician
Category: Buick
Satisfied Customers: 27666
Experience:  GM Grand Master Technician 2007. 11 years experience.
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Buick LeSabre I rebuilt a 4T65E transmission due to a harsh

Customer Question

I rebuilt a 4T65E transmission due to a harsh shudder in first gear under acceleration. The shudder was resolved after rebuild, but two new problems exist now. 1st: Upon initial start up ,after the car has sat for an extended duration (over night),when directly shifted to D4 there is a 10 second hesitation before foreward movement occurs. However, when shifted directly into reverse there is no hesitation. Note: line pressure comes up to spec immediately upon initial start up. 2nd: No up-shift from 3rd to 4th under half throttle acceleration. Up-shift to 4th only occurs under heavy acceleration. When the PCM commands a 4th gear up-shift it also increases line pressure to maximum out put. Maximum line pressure is present with or without a successful 4th gear up-shift. Maximum line pressure only exists when the computer commands a 4th gear shift. Note: I did replace the PCS solenoid during the rebuild.
Submitted: 3 years ago.
Category: Buick
Expert:  GM Tech (Cam) replied 3 years ago.
Hello, I'm Cam. Please include all the details about your issue so I can accurately advise you. I cannot see your vehicle so please be detailed.

Did you replace all the seals, pistons and air check the transmission prior to assembling it?
Customer: replied 3 years ago.

Yes, a complete rebuild was completed. All seals, gaskets, o-rings, frictions, steels, bushings, and bearings were replaced. I did air check all clutch packs before final assembly. I did not derermine what caused the origional shudder problem, but it does not exist now. I did check line pressure prior to the rebuild and it appeared to be up to spec in all my tests. There were no DTC's prior to the rebuild and there are none now. I did also replace the manifold pressure switch. I have back probed the harness connector and tested both shift solenoids, manifold pressure switch, PCS solenoid, and trans temp sender. Everything passes the tests I have performed. The PCM does not seem to be aware of any issues at all.

Expert:  GM Tech (Cam) replied 3 years ago.
Ok, do you dismantle the valve body diring the rebuild?
Customer: replied 3 years ago.
Yes, I completely dismantled the valve body. I cleaned everything throughly. All of the valves appeared to be in good condition and moved freely in there bores. I also tested all of the electrical components for proper resistance values. I also replaced the torque converter. I also replaced the 3rd clutch molded piston and 2nd clutch molded piston. Any info would be great. Thank you.
Expert:  GM Tech (Cam) replied 3 years ago.
Does the delay happen in manual 1?
Customer: replied 3 years ago.
No delay in manual 1,2, or 3. Once shifted to reverse or manual 1, 2, or 3 prior to D4 there is no delayed engagement into D4. Trans shifts and functions great in first three speeds. Once the PCM requests a 4th gear up shift it also increases line pressure to max out put by reducing PCS amperage to one tenth of an amp. The PCM actual PCS amperage and desired PCS amperage are the same.
Expert:  GM Tech (Cam) replied 3 years ago.

DEFINITION: A large engine RPM increase is noted in first gear, Drive range, with little or no vehicle forward speed increase. Second, third, and fourth gear operation are normal. Shifts into first gear are soft or do not occur. First gear ratio is 2.921:1.

Automatic Transmission Fluid Level

Low fluid level

Transmission Main Line Pressure

Low transmission main line pressure

Oil Filter Assembly

The oil filter assembly (100) is missing, plugged, or damaged.
The oil filter seal assembly (101) is missing or is damaged.

Accumulator and Manual 2-1 Band Servo Assembly

A loose or damaged forward band servo oil pipe (124)
Loose manual 2-1 band servo cover of accumulator cover bolts (103, 131)
A missing or a damaged manual 2-1 servo cover gasket (105)
A damaged accumulator cover spacer plate assembly (134)

Forward Band Servo Assembly

The servo piston oil seal ring (18) is missing or damaged.
The servo piston (16) is damaged or stuck in the servo cover (13).
The servo piston cushion spring (19) or the retainer (20) is missing or damaged.
The servo piston pin (21) is not engaged to the forward band assembly (688).
The forward band assembly (688) is worn or burned.
The forward band assembly (688) is disengaged from the anchor pin (117A).
The band anchor pin (117A) is loose or missing.

Control Valve Body Assembly

The 1-2 shift valve (318) is stuck or binding.
The #3 ball check valve (372) is missing.

Input Clutch Assembly

The input clutch sprag assembly (722) is damaged or misassembled.
The input clutch housing oil seal rings (628) are missing or damaged.
The input clutch housing ball check valve assembly (633) is missing or damaged.
The input clutch piston inner/outer seals (634/635) are missing or damaged.
The input clutch piston (636) is damaged.
The input clutch plates (645-658) are worn.

1-2 Clutch Roller Assembly

The 1-2 clutch roller assembly (683) is damaged.

Customer: replied 3 years ago.
Thank you for your time and info Cam. I will check those items.
Expert:  GM Tech (Cam) replied 3 years ago.
OK.
Please reply back if you need additional help or press ACCEPT so that the question may be closed out. You can reopen it at any time by replying to it and I will answer ASAP. PLease keep in mind that as experts on this site, we are only compensated for our time spent helping customers once ACCEPT is selected. Thanks again for using Just Answer. Cam.
GM Tech (Cam), Buick Technician
Category: Buick
Satisfied Customers: 27666
Experience: GM Grand Master Technician 2007. 11 years experience.
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Chat Now With A Buick Mechanic
GM Tech (Cam)
GM Tech (Cam)
Buick Mechanic
27666 Satisfied Customers
GM Grand Master Technician 2007. 11 years experience.