ALL possible causes for no forward gear in 4t65e transmission? Added some clips

AZilla83

Jr. Member
Joined
Sep 2, 2021
Messages
36
Points
8
Make
GM
Model
Buick Lucerne CX
Year
2007
Miles
200,000
Engine
V6 3.9L
I recently bought a 07 Buick Lucerne CX. No check engine light when I initially bought it, of course they must've reset it, bc next day code popped up for shift solenoid B stuck on. It still drove decent but wouldn't go above 50mph. Once you hit 50mph it would just rev & rpm would max out, so I would just let of the gas until slowed below 50mph & it would engage again. Watched some YT vids & planned on replacing both shift Solenoids that weekend(it was gonna be all day event) as I needed vehicle to commute to & from work. It didn't make it to the weekend. Slowly lost drive gear all together, but would go in low 1 & 2. Then lost movement in ALL forward gears. Still goes in reverse. So I did more research, opened it up n replaced All the Solenoids(shift a & b, PCC), new wiring harness & was gonna replace the forward band, but it wasn't broken. Important to note there weren't any metal shavings in the pan, all the clutches & friction plates were in good shape. Reassembled, but still no forward gears! The only code it has now is P2341secondary air injection flow or something, which is NON transmission related. So I'm hoping someone can gimme a list ALL possible causes for no forward gears? You can hear & feel it shift into reverse, then Neutral, but when you go into Drive or below, you can't hear or feel anything. Cycled all the way down to 1 then back up into P.
 

grcauto

wrench
Joined
May 29, 2014
Messages
1,052
Points
48
What kind of line pressure do you have?
 

billr

wrench
Staff member
Joined
Mar 12, 2007
Messages
7,444
Points
63
How do you know the clutches are all OK; have you disassembled the trans? The next time you have the pan off, remove the VB and do some air-checks. There are probably sprag clutches (no hydraulic operation) that are best checked with the trans disassembled.
 

AZilla83

Jr. Member
Joined
Sep 2, 2021
Messages
36
Points
8
How do you know the clutches are all OK; have you disassembled the trans? The next time you have the pan off, remove the VB and do some air-checks. There are probably sprag clutches (no hydraulic operation) that are best checked with the trans disassembled.
I didn't pull the whole tranny out & disassemble it. I removed driver side tire & strut, cradle bolts & loosened passenger side cradle bolts. Which allowed me to get the side cover off & pull out all the clutches. I did this to replace the forward band which upon research, is usually broken & the cause %90 of the time. LOL only it wasn't... I'm no mechanic, but watched alot of YT vids on teardowns of 4t65e, so I took my time to inspect all the gears, teeth & friction plates before I reassembled it. They were in good shape & there wasn't any kind of metal shavings in the bottom of the pan. So I'm kinda stumped...
 

AZilla83

Jr. Member
Joined
Sep 2, 2021
Messages
36
Points
8
I did see vid on how to air check each clutch with air hose, unfortunately I do not have a compressor. Also well I had it taken apart, I thoroughly cleaned the valve body, the lil shift filters & accumaltor with carb cleaner n then sprayed & wiped em down with WD-40. I made sure all checkballs were in & in correct holes as well.
 

billr

wrench
Staff member
Joined
Mar 12, 2007
Messages
7,444
Points
63
I am not a trans expert, and have no experience with this type trans. However, I did peek at an IPB for it (by the way, is yours the "20 pan screws version"?) and see that the FWD drum/band is buried deepest in the trans. So, you pretty much did disassemble the trans to get to that; even though the trans case stayed on the car. Did you disassemble each clutch/drum unit, remove the snap rings and pull out all the plates? Did you peek at the inner and outer seals on each clutch "pressure plate"? How about all the seals (iron and plastic) at the various shaft-to-hub fluid "rotary unions"? Going that deep into the trans, I hope all that stuff got replaced, but gotta ask...
 

grcauto

wrench
Joined
May 29, 2014
Messages
1,052
Points
48
You have a funny way of describing what you did. It's sounds like you didn't remove the transaxle which is required to pull the clutch packs with the drums. Also the pump you have to pull it for that as it's under the converter and at the input.
You say 'I didn't pull the whole tranny out & disassemble it.' To do the things you say you did you HAD to.
 

AZilla83

Jr. Member
Joined
Sep 2, 2021
Messages
36
Points
8
Not sure on how many pan screws LOL but 20 sounds about right(a lil overboard in my opinion). I wasn't able to take apart 3rd or 4th clutch drums, as I believe you need a hydraulic press to open & close em? But as I was putting em back together I checked the teeth inside on each plate(though not sure if broken ones would have an impact on the lack of forward engagement). I also inspected the rods on the planetary gear assembly, to ensure they weren't too loose, both the steel & golden washers were visible (I saw on YT if only one was visible, it needed to be taken apart & washers replaced). I made sure all plastic & steel washers were on correct(held in place with tiny dabs of gasket maker) upon reassembly. All rubber o-rings were in good condition as well. Not sure about "pressure plate"... There was only one separator plate, between channel plate & valve body thats black & has 2 lil shift solenoid filters, that holds check balls in the channel plate. It was in good condition... Btw I appreciate the time you've given in trying to help!
 

AZilla83

Jr. Member
Joined
Sep 2, 2021
Messages
36
Points
8
You have a funny way of describing what you did. It's sounds like you didn't remove the transaxle which is required to pull the clutch packs with the drums. Also the pump you have to pull it for that as it's under the converter and at the input.
You say 'I didn't pull the whole tranny out & disassemble it.' To do the things you say you did you HAD to.
I apologise, if I'm not describing it properly or using correct terms. I'm not a mechanic, I've just watched vids on YT & tried to self diagnose the problem. I didn't fully pullout the tranny as I don't have the proper equipment. I did pullout all the clutch hubs & drums, to get to fwd band by first removing the driver side tire & strut, cradle bolts, then loosening the passenger side cradle bolts, as well as top engine mount. Which gave me enough room to remove the side cover(method saw on YT). I actually nvr pulled out the trans axle rod inside the tranny as it was secured to the other end. LOL I'm sorry, it just donned on me, you're talking about the axle that goes between the tire & tranny? Yes, obviously I did remove it, I just considered it as part of taking off the tire & strut. ‍♂
 

billr

wrench
Staff member
Joined
Mar 12, 2007
Messages
7,444
Points
63
Do you have a good IPB (Illustrated Parts Breakdown) of the trans to post, so we can all identify the parts we are discussing? If not, I will post a link to one.
 

bp042665

transmission guy
Joined
Nov 26, 2012
Messages
760
Points
28
Location
Iva South Carolina
it sounds like a sprag problem or even a stripped spline or a broken shell with out taking it all the way out its hard to tell
 
Top