GM 4T65E Hard Shift Fix

Summary

The GM 4T65-E transmission was produced between 1997 and 2011 and was used in many GM FWD vehicles with the Buick 3800 Series II V6 which is arguably one of the best engines ever made, but that is another story ..

One of the most common problems is the P1811 code or 'hard shifting' after the transmission and engine reach normal operating temperature. Usually after coming to a stop and moving off again. My 2002 Chevy Impala happened to have this problem, which surfaced after I had the dirty transmission fluid flushed - is seems the dirty fluid hid this issue.

• The problem is often caused because the bores in the accumulators become too smooth and the rubber seals in the pistons will grab or bind up when the transmission fluid is hot.
• This causes a long shift which is detected by the computer, to compensate the line pressure is increased. Mostly as a fail safe to prevent slipping clutches from burning up for example.
• The result is very hard gear shifts, especially 3rd to 4th when the torque converter is locked up.
• There are other causes of the hard shifting from things like a faulty MAF sensor, to faulty shift solenoids among other things, servicing the accumulators is not much more work than doing a fluid/filter change (which is probably overdue anyways) then you can at least rule this out.

There are two options, one cheaper than the other:

1. Cheap and nasty option is drop the pan, remove the accumulators, scuff the bores, change the filter & put it all back together. Refill with BrandX Dex III ATF and call it a day.
2. The more expensive route is to also install a shift kit while we're in there & replace gaskets and seals in the accumulator, refill the transmission with Dexron VI or Allison Transmission TES 295 ATF fluid.

Parts & Fluids

Following the more expensive route this is what you'll need:

• 4T65E Shift Kit Combo Kit from Triple Edge Performance. Everything you need, this is what I got.
• ZZPerformance also sell a 4T65E Shift Kit.
• Allison Transmission TES 295 approved fluid. If you cant find the real stuff locally stocked anywhere, Amazon currently (09-Jul-13) sell Mobil Delvac in a 1 gallon pack and a 4 pack containing 4 gallons. Qualified for free shipping when I ordered the 4 pack.
• Brakleen - used to clean the parts removed - it leaves no residue and should mention this on the can.
• I found one can was only just enough for cleaning the pan, accumulators and those aluminum pipes. I would suggest two cans. This stuff is pretty toxic, spray the parts down outside away from everything into another plastic pan.
• List of tools to be added.
• Some gloves probably a good idea too.

The TransGo shift kit also includes parts that can only be replaced during transmission rebuild. The first side of the info sheet as shown above is only relevant when doing this fix on the accumulators.

Why TES 295

I spent a number of hours researching automatic transmission fluids and this is what I found:

• All Dexron-III licenses expired permanently at the end of 2006, and GM now supports only Dexron-VI fluids for use in their automatic transmissions, it is backward compatible with Dexron-III.
• Fluids asserted by their manufacturers to meet Dexron-III standards continue to be sold under abbreviated names such as Dex/Merc, but the licensing system no longer exists. These fluids are not regulated by GM.
• Allison Transmission TES 295 is a good replacement for transmissions specifying Dexron-III. It exceeds the specification, doesn't lose viscosity with age or oxidize as easily as Dexron-III. It is also rated to -54 °C, desirable here in Fairbanks Alaska where winter temps range from -20 °C to -50 °C.
• If you don't want to spend a bit extra then go for Dexron-VI.
• TES 295 and Dextron-VI work out cheaper due to extended drain intervals.
• Former Allison Transmission Fluids Engineer answers question about TES 295. This is where I got most of the info about TES 295 from, there are about 60 pages of posts so I mostly skimmed over them reading the replies from Tom (hzjcm8).

The Procedure

Most of the information is borrowed from these forum posts, so the credit goes to these guys for writing up what they did:

http://www.gmforum.com/4t65e-hd-147/installing-shift-kit-4t65-hd-transmission-279684/
http://ls1tech.com/forums/ls4-performance/1311880-trans-go-shift-kit-installed-first-impressions.html
http://ls1tech.com/forums/ls4-performance/628840-shift-kit-install-very-detailed-56k-go-watch-movie.html
http://www.w-body.com/showthread.php/32132-4T65E-Do-It-Yourself-Shift-Kit-Instructions-and-Install-Guide

• Ideally you'll want to do this when the transmission fluid is hot. In my case it was a 20 mile drive to my wife's parents place where her dad helped me do this - so the fluid was good and hot. I left the car idling while we got everything ready.
• The ramps we had were too high for the low plastic bumper, so we jacked the car up with a trolly jack, and placed 2 axle stands under the sub frame, and two where a jack normally goes when changing a tire.
• I placed a big piece of cardboard under car, and the large plastic tray that can hold at least 4 to 6 gallons so it's not too full when it's time to move it.
• DISCONNECT THE BATTERY NEGATIVE LEAD!
• Images are from different places, they are not all from the same car, so things look different in some of them, but the transmission it self is the same.

Dropping The Pan

• The pan bolts are 10mm. Carefully loosen each pan bolt, then at one corner loosen them more - I did this on the front middle corner.
• You may need a flat screwdriver to carefully pry the pan open - do not leaver against the soft aluminum.
• Once the fluid starts to flow you can carefully undo the bolts to drop one corner down more to let the fluid out.
• Once it's mostly out hold the pan up, remove the bolts (put them in a cup for safe keeping), then tip the rest of the fluid out of the pan into your plastic tray.
• Fluid will continue to drip or “rain” out for some time.

• Take the pan and gasket away outside somewhere to clean it up. In another plastic tray hold the pan up vertical with the magnet at the bottom and spray it with Brakleen back and forth from top to bottom making sure it's dissolving the fluid and gunk out of the pan leaving a clean surface. You should be-able to see the brakleen evaporating leaving no residue and a perfectly clean pan.
• Put the pan on a clean surface facing down so nothing lands or falls into it. Avoid the temptation to touch or wipe it with a cloth.

Accumulators

• First the filter has to come off, it's held on by the neck, the plastic is on the brittle side so be careful with it. It took about 5 mins to wiggle it out, I used a screw driver to apply some downward pressure where the filter neck is, and I wiggled the other end of the filter with my hand, it eventually came off. Don't leaver the screwdriver against any of the exposed parts of the transmission, and especially where the pan and seal bolt together.
• Undo the 4 bolts shown, the pipe with the rubber join will just pop out, the other two will just pull out of the accumulator with a bit of wiggling as it's removed - these pipes are made of aluminum so be careful not to bend them, or they might grab and never come out.

• When you undo the accumulator housing and remove the pistons, make a note of which one goes where, the springs are different! The 2-3 accumulator has the stronger thicker looking spring (in my case).
• The accumulator bores will be mirror smooth - the root of the problem!

• Service the accumulators by giving them a light scuff with the supplied Scotch Brite. Once done, give it a good dose of Brakleen.

Putting things back together

Try to get everything clean, and keep it clean.

The bolts that hold the accumulator together, and the 4 that bolt it to the transmission should be torqued to 97 inch pounds .

To put the new filter on, locate it and carefully tap the neck back into place with a plastic mallet.

The pan seal/gasket should be reusable if its the rubber coated steel type. Pan on, bolts in and done up finger tight, gradually tighten each bolt alternating between sides, then torque each one to 120 inch pounds, go around one last time to make sure you didn't miss one.

Just shy of 8 quarts came out. I put a full 8 back in:

Tip about 6 to 7 quarts back in, start the engine, go through the gears, check the level between putting about 1/2 a quart in at a time, until it's full, I then did a little forwards and backwards on the driveway, topped it off to full mark again, then took it for a drive, after that the last 1/2 a quart to the full 8 brought it up to about half way on the dipstick, and this is where I left it rather than crack the next bottle open.

Since the battery will have been disconnected for a while, the PCM will reset, gear shifts etc may be a little different for a couple of days until it's finished relearning.

Bolt Torque Settings

One thing none of them mention are the torque settings for the bolts:

You will need an inch pound torque wrench.

• 8mm socket and ratchet.
• 10mm deep well socket and ratchet.
• Torque accumulator bolts to 97 inch pounds.
• Torque pan bolts to 120 inch pounds.

I found the pan bolts on mine were barely tight when I undid them.

Chevy Impala Passlock Bypass

Many people reportedly have this problem with their late 90s to early 2000s GM vehicles.

The problem in a nutshell is that the car wont start, the security telltail will flash. You have to go through the 10 minute reset process, or even the 30 minute reset sometimes. Understandably some people get pretty annoyed when their car does this randomly, or even every time in some cases. Also the security warning may have been coming on while driving.

What is Passlock?

It's a security feature on the ignition barrel where only the correct key will activate the passlock. The passlock normally provides a fixed value of resistance that the BCM (Body Control Module) reads, and if it's with-in range along with some other security checks it does, it'll allow the car to start.

If it's too far out of range it wont start and the security light or telltail will flash. On the Impala's Message Center the display will cycle between blinking “security” twice and the red battery. After waiting 10 mins with the key in the ON position it will cycle between security and battery with out blinking, turn the key to OFF, then back to ON and CRANK and it should start.

So what's the problem?

The contacts in the passlock module become worn, the connectors are not gold plated so corrosion can occur in more humid places, and if you're near the ocean the salt air wont help much either. The worn contacts and/or corrosion changes the resistance the BCM sees and the new value has to be relearned via the 10 minute reset.

I happen to have a 2002 Impala with this problem.. At the time I lived in Fairbanks Alaska where the climate is very dry, my passlock would play up maybe once every couple of months or so and with one reset the problem would be gone until next time. During a trip to Anchorage where there is a lot more humidity, the passlock required a reset every morning, and at least one 30 min reset while we were there.

Finding the solution

Upon searching for answers there are many endless forum threads about it:

• Bypass the passlock module it self with a fixed value resister.
• Completely replace the module at a much higher cost.
• Car alarm systems with/or remote start systems bypass the passlock.

The passlock is connected to the BCM via three wires, yellow, black and white. All you need to do is cut the yellow wire from the BCM to the passlock, and place a fixed value resister (say 2k2 Ω) between the end FROM the BCM and the black wire, the black wire must remain joined. The yellow going TO the passlock is left disconnected. Once the new value is learned, the passlock issue should never return. Simple as that, the hard part is accessing the wires.

If you look hard enough there are some detailed instructions around, like this article for the Pontiac Grand Am. But nothing detailed for the Impala on how to get at the passlock wires. The BCM looks the same as the one shown in on Grand Am linked above. But connectors C2 and C3 are wired quite differently with different colors, and unused pins in different places. My BCM had 4 sets of numbers on it, the one that seems to identify it as an Impala BCM is 10445875, the other numbers didn't turn up much. None of the schematics I found online matched mine.

It's debatable if doing this fix on the BCM end would be any easier since you'd be cutting, stripping, soldering wires in-between two bunches of 24 wire connectors while laying upside down in the drivers side foot well. Removing a couple of extra panels and having easier access to the wires at the ignition end will be much easier, and this way you know you're dealing with the right wires.

For what it's worth I used my multimeter find out where the yellow and black actually goto on the BCM end of the loom. The BLACK wire came out on C3 (the pink connector) pin B12, and the yellow on C2 (the middle grey connector) pin B3. If you're going to do this on the BCM end, be sure you have the right wires, otherwise the magic smoke might leak out of something.

Bypassing the Passlock

This will take a couple of hours from start to finish. You'll need some basic tools, and know how to solder. If you're not into soldering you can use a solderless method such as this.

First disconnect the battery negative terminal!

Tools I used

Remove the drivers side kick panel - this holds the floor light.

Then remove the steering column filler panel as above, remove the two screws at back above the pedals then pull the panel towards the seat, it'll just pop out of the clips that hold it. Carefully remove the plug from the boot/trunk release button - use a small flat screw driver to lift the one green clip which holds it in place and wriggle it out, not the smaller white ones.

This will reveal the aluminum panel that is screwed and bolted with 4 10mm bolts - to get these undone you'll need a socket set and will have to get right down into the foot well upside down.

With all that out of the way you can now easily access the passlock wires where they come out from the back of the ignition barrel.

These are the three yellow, white and black wires that are of a much thinner gauge. Did you disconnect the negative terminal from the battery?

The other cabling to the steering wheel makes for a handy flashlight holder..

• The yellow wire is easy, just snip it.
• The black wire you could also just snip and rejoin, but I chose to carefully remove a section of insulation.
• The 2k2 Ω resister goes between the back wire and the yellow wire FROM the BCM.
• The yellow TO the passlock module is left disconnected.
• Now the BCM will always see the fixed value resister we installed.

Resister installation. One end connected to the yellow from the BCM, I put some heat shrink down over it once I had soldered the yellow wire end. The other end of the resister will attach to the black where the insulation is removed.

I slid the heat shrink back up, I didn't bother “shrinking it”. Used the exiting insulation tape and pulled it back down over the solder joins and cable tied it twice to keep it all in place.

Reconnect the battery.

I had to do the 30 minute reset process, the car started on the 3rd attempt.

3 months after doing this mod, I have had no passlock issues!

Note: The wiring to the drivers side ABS/wheel speed sensor is broken, so the ABS and traction control system disables it self - is why the ABS and track off lights are (always) on.. I actually prefer those two nanny features to be off, especially on Alaska's iceroads.

10 and 30 Minute Learn Procedure:

1. Turn ON the ignition, with the engine OFF.
2. Attempt to start the engine, then release the key to ON (vehicle will not start).
3. Observe the SECURITY telltale, after approximately 10 minutes the telltale will turn OFF.
4. Turn OFF the ignition, and wait 5 seconds, then try and start the car.
5. If it does not start repeat steps 1 through 4, 2 more times for a total of 3 cycles/30 minutes.
6. The vehicle is now ready to relearn the Passlock Sensor Data Code and/or passwords on the next ignition switch transition from OFF to CRANK.
7. IMPORTANT: The vehicle learns the Passlock Sensor Data Code and/or password on the next ignition switch transition from OFF to CRANK. You must turn the ignition OFF before attempting to start the vehicle.
8. Start the engine. The vehicle has now learned the Passlock Sensor Data Code and/or password.

2022 Update

Around 2017 started experiencing an array of problems starting with HVAC being dysfunctional, security message being displayed again, radio security lockouts, DIC stopped working, and finally randomly not starting grrrr. The car was no longer a daily driver but more a garage ornament at this point, I used it once or twice a year..

Long story short I replaced the key ignition module and the BCM. Once the contacts in the ignition go bad (as they do in the passlock module) they can fry the BCM and both have to be replaced.

Initially I replaced the key ignition module which fixed the radio security lockouts, but nothing else. 

The BCM I got from Highway 71 Autoparts - they will flash and ship them ready to go. After replacing the BCM the gremlins are gone and everything works again.