Apr 26, 2016, 01:29 PM
Last edit by: IB Advertising
See related guides and technical advice from our community experts:
Browse all: Tranmission Guides
- Camaro and Firebird: Transmission Diagnostic Guide
Guide to diagnose trouble and recommended solutions
Browse all: Tranmission Guides
LS4 Transmission Problem Thread (4T65-HD); Current Total Inside
Registered User
Joined: Mar 2019
Posts: 1
Likes: 0
Slug and clunk in 2nd that was a brake grabbing. Same transmiand thai is SUVs and Tr Same transmission that is in all the heavy trucks and SUVs I've only have one that I could funny with the clock and slip or slipping clock I should say second I was in a 06 Impala all the rest of the Vans and trucks have and have a soul tranny.
Teching In
Joined: Jan 2015
Posts: 8
Likes: 0
Keep your coolers flowing well! Long story short, keep your transmission cooler flowing properly, Id recommend backflush every 10-15000 miles.
If not it could clog and cause the trans to blow a seal.
2006 Pontiac Grand Prix GXP
TEP HPS1 transmission installed at ~165,000miles (4th trans for car)
201,000+ miles on car.
Just over 35k miles and 2years on our transmission now and was still strong.
I installed trans with Hayden 679 cooler bypassing rad cooler and Amsoil OE Trans fluid, hardly saw temps over 170.
Usually hung out around 155-165 even after 3 straight hours of driving.
MY laziness of not flushing cooler and not doing fluid/filter maintenance,
cooler input clogged, torque converter fluid seal blew.
50-65mph and drive power was lost. Get it home and the plastic cover on bottom of bell housing was melted... , so flush cooler, seemed clogged,
after back-flushing cooler and refilling trans with about 7 quarts,
tested flow with return line disconnected, had great flow again and drive and reverse is back.
I believe its just the o-ring on the input shaft that the converter snout slides over, or at worst we need new converter, I HOPE its just an external seal....
Car will still go forward and backward, but is dribbling fluid off the bottom of torque converter.
She just got put up on rollback for ride to shop that's going to do repair since I don't have access to a lift right now.
You have been warned, or maybe I missed someone else's warning? lol
Planning now to use 2 smaller coolers running in parallel, I want to use a y-split from the transmission out line to the 2 coolers, then use another Y to join the outputs from the coolers and send it back to transmission. Thinking now I may need one-way valves to make sure one cooler doesnt start feeding into the others output.
If not it could clog and cause the trans to blow a seal.
2006 Pontiac Grand Prix GXP
TEP HPS1 transmission installed at ~165,000miles (4th trans for car)
201,000+ miles on car.
Just over 35k miles and 2years on our transmission now and was still strong.
I installed trans with Hayden 679 cooler bypassing rad cooler and Amsoil OE Trans fluid, hardly saw temps over 170.
Usually hung out around 155-165 even after 3 straight hours of driving.
MY laziness of not flushing cooler and not doing fluid/filter maintenance,
cooler input clogged, torque converter fluid seal blew.
50-65mph and drive power was lost. Get it home and the plastic cover on bottom of bell housing was melted... , so flush cooler, seemed clogged,
after back-flushing cooler and refilling trans with about 7 quarts,
tested flow with return line disconnected, had great flow again and drive and reverse is back.
I believe its just the o-ring on the input shaft that the converter snout slides over, or at worst we need new converter, I HOPE its just an external seal....
Car will still go forward and backward, but is dribbling fluid off the bottom of torque converter.
She just got put up on rollback for ride to shop that's going to do repair since I don't have access to a lift right now.
You have been warned, or maybe I missed someone else's warning? lol
Planning now to use 2 smaller coolers running in parallel, I want to use a y-split from the transmission out line to the 2 coolers, then use another Y to join the outputs from the coolers and send it back to transmission. Thinking now I may need one-way valves to make sure one cooler doesnt start feeding into the others output.
Last edited by AndrewGXP; Feb 23, 2021 at 11:11 AM. Reason: I HOPE it is just an external seal....
Teching In
Joined: Jan 2015
Posts: 8
Likes: 0
FWD car transmission are the 4Ts, grand prix/impala/monte carlo/lacrosse have the 4t65e-"HD" transmissions which are glass weak when stock and mounted to the LS4 engines, probably iffy on the 3.8 S/C motors also. We all wish we could easily put a 4L or 400r in our cars, I think only an elite few have converted to RWD.
Teching In
Joined: May 2021
Posts: 1
Likes: 0
2007 gxp no mods 123k shelled trans due to cooler lines leaking. should have paid closer attention but the driveway was clean. Had it rebuilt and its great now.
Last edited by Bill Johnson; Jun 4, 2021 at 10:38 PM. Reason: add info
Well factory had a complete fail at 109569, then replaced with a Best Buy Tranny, there tranny made it to 131123, so they are very stand up once it takes them 48 to 72 hours to get back to you once you file the claim, they paid all labor and transmission was replaced, took about 6 days car was running again, and a month and a half on labor reimbursement, well at 134,222 I put in reverse in the driveway and thought I heard a pop, you can hear it making all kinds of noise, nothing engaging in any gear, I only use car for a 34 mile round trip back and forth to work , not beating the **** out of it, so I got what a whole total of may 3,000 miles on this Best Buy Transmission, in the process of filing another claim still have another 2 years left on the warranty and was told with the last transmission they would stand behind the warranty again, let's see how it goes, they have emailed back but no phone calls, so 72 hours so far. This is just a nightmare honestly, I would say there customer service and warranty department has been next to perfect, there transmissions, are garbage.
