Buick 4T65E hard shift *LONG*

[TMoto]

Hey guys, first post. Sorry it's so long, but felt some background would be helpful. Lots of good info. here, but sometimes all the opinions can be overwhelming.

I recently bought a 2000 Buick Century with 123k miles on the odometer and with what I believe is the 4T65-E transmission and discovered that at times it will shift hard. It only does this after about 25-30 minutes of city driving, otherwise it shifts well when it's cold or on the highway. The shifts aren't bone-jarring, but noticably harder, and I went to AZ to see if any codes came up on their scanner and none were found. The fluid is bright red, does not smell burnt, and appears to be in good condition. However, this could also be because the car lot recently replaced the fluid. Who knows, but I'm in the process of replacing all the fluids and filters regardless.

I've been digging around on the internet looking for causes and possible solutions and discovered that it appears to be related to shift timing once it's warmed up and the fluid is hot. If it consistently takes longer than approx. 0.6 seconds to shift, the pcm will raise line pressure to prevent slippage. I've heard some instances where others have had these symptoms only in the summer but not in the winter, so I think it relates to heat but these cases I think are inconsistent.

I'm not currently in a position to be able to get a replacement tranny or rebuilt this one, but have found there are some remedies that may extend it's life. The first is to install a shift kit and the most recommended one is from TransGo. Their web site claims to solve the problem by shortening the shift time, and at least one reputable transmission shop recommends trying it. I have no problem doing this myself since I installed a similar one years ago on a truck I owned with a TH-350.

I've purchased a Wix filter for when I drop the pan, but my question for you guys relates to fluid and possible additives and/or flushes. I won't be having any power flushing done, and will be doing my own pan drops/fluid exchanges as necessary, but should I run a chemical flush treatment from ARX, BG, Lube-Gard, etc.? I've read that Valvoline MaxLife would be a good choice for fluid, but would a Dex VI be better? If so, what brand? I've also read that Lube-Gard red is a good product as well. Should I add that to a standard Dex III or Dex VI like Super-Tech, or go with MaxLife and add to that?

Also thinking about adding a tranny cooler as well.

Thanks in advance for all the help.



Cliffs:
4T65-E trans has intermittent hard shift when hot.
Found that a TransGo shift kit will help solve problem.
Considering a chemical flush like ARX.
Looking for fluid recommendation.
Also considering Lube-Gard red.
What say you...

TIA

 

[pbm]

My 02' Century has similar mileage and the A/T shifts beautifully using Mobil 1 ATF. I've also added LG red both times that I changed the fluid (at 36K and 96K).
I would run some Auto-RX to clean the tranny out and then change to Mobil 1 or Amsoil or Redline ATF. I have heard good things about 'shift kits' but I've never felt the need to install one.

 

[EvanD]

I would leave it alone unless your ready to pay for a rebuild. Your gonna stir up a bigger problem.

I would drain the fluid not a flush and hope it lasts.

 

[bmwtechguy]

On the shift kit, make sure you know what you are getting in to. The valve body is in the side pan on these and on some cars is hard to impossible to get this pan off with the unit in the car. Just a heads up. I have used Auto-Rx on many automatic units and they always shift better afterwards. A cooler on these units helps to prolong the life of both the fluid and the transmission. I installed a large cooler and inline filter on our 94 Buick when we bought it, and that unit went until about 278k miles when it was hit hard on the left front and we retired it.
On the fluids, Maxlife or Dex VI would be fine choices for retail. I have used Mobil 1 ATF and had good results in this transmission. Most of the miles in our Buick Lesabre were with Amsoil ATF. The fluid looked fairly spent after 100k miles, however, even with the large cooler and inline filter. I don't think these units are easy on fluid, IMO.

Lubegard would be something to consider using if you stick with the oem fluid, one of the DexIII or DM3 type fluids. But if you use something better like Dex VI or even Amsoil ATF, I don't think it will add much to those fluids' performance.

Check to see if yours has a vacuum modulator. They may have done away with it on your later model unit, but when vac modulators lose vacuum such as a vac hose leak, that can cause late/harsh shifts.

If you do go the ARX route, just put 6 oz in your current fluid and run it at least 1000 miles. I always run mine longer, like 2 or 3000 miles. You could then use 2 oz in the PST fluid and the remaining 4 oz in the engine as a maintenance dose at some point.

I have some of the Lubegard flush that I got for $1/bottle on clearance, but since having such good results with the ARX, I have been just using the Lubegard tranny flush as an engine flush before oil changes to use it up. The Lubegard flush is not really harsh solvent stuff, just some detergent/dispersant additives. IIRC, Amsoil now makes a similar dual-use non- solvent product now that is not too expensive. HTH

 

[bepperb]

I'd be real hesitant to assume a used car lot is changing the ATF on car, even if it was to clean up the shifts. So that's an obvious thing to try. A cooler also seems like a good idea, but in CO I would probably buy a plate cooler that has a cold weather bypass built into it.

 

[Blokey]

We had exactly the same hard shift issue with our '01 Olds Intrigue that also uses the 4T65E trans. We replaced the PCM and the problem never occurred again. The car now has 120K miles on its original trans. In that time I've changed the filter twice and I've done many drains & fills using RL D4, RP MaxATF and M1 ATF. When I changed the filter the first time I replaced the pan with one with cooling tubes and a drain plug which made subsequent fluid changes a breeze.

 

[sciphi]

1. TransGo shift kit: Install what you can through the pan. It's ~80% of the kit, and the most important 80% for correcting the shifts. Installed that part myself.
2. ARX might help. I've used it successfully in my car's 4T65.
3. MaxLife ATF is an excellent choice. Presently using it, it works well.

It can be corrected with the ARX, shift kit, and new fluid. That's what I did for mine. It's worked for a long time so far.

 

[eljefino]

These cars modulate the line pressure with solenoids (and shift with them as well.)

If you can remove the side cover, there are about three in there, around $50 apiece. They get tired over time. The default line pressure is "jarring" and the solenoid dithers to bring it down to reasonable.

A shift kit generally makes firmer shifts anyway, which supposedly *save* wear and tear on the trans. It sounds like by default you are getting this behavior.

Dex VI has a great rep but is thin, if your issue is temp/viscosity related it'll be worse. Maxlife is on the thick side. However, if your issue is temp affecting the solenoids (happens sometimes) the DexVI will be great.

 

[TMoto]

Originally Posted By: bmwtechguy
On the shift kit, make sure you know what you are getting in to. The valve body is in the side pan on these and on some cars is hard to impossible to get this pan off with the unit in the car.

I have no intentions of getting too deep into the trans, especially pulling off the side cover since it's fwd. This kit involves dropping the accumulator and replacing some springs and spacers which can be accessed easily once the pan is removed. Now on the TH-350 from my pickup I believe you are correct about getting into the valve body.

Quote:
Check to see if yours has a vacuum modulator. They may have done away with it on your later model unit, but when vac modulators lose vacuum such as a vac hose leak, that can cause late/harsh shifts.

I'll look into this, thanks. Wouldn't something like this show symptoms all the time though? Mine is somewhat intermittent, but only occurs when it's fully warmed up. I didn't mention this in my OP, and not sure if it's relevent, but the hard shift is only on upshifts, never on downshifts and I don't hear any unusual sounds.

Quote:
The Lubegard flush is not really harsh solvent stuff, just some detergent/dispersant additives.

Speaking of harsh solvent, I was cleaning out some old stuff out of the garage recently and found a new can of K&W Trans-X which I'm pretty sure is a solvent. It's pretty old, and I don't think I'd want to put it in the tranny anyway, but since the can is new I can't seem to bring myself to toss it. Maybe I'll use it to clean the wrenches when I'm done.

 

[TMoto]

Originally Posted By: bepperb
I'd be real hesitant to assume a used car lot is changing the ATF on car, even if it was to clean up the shifts. So that's an obvious thing to try. A cooler also seems like a good idea, but in CO I would probably buy a plate cooler that has a cold weather bypass built into it.

Well, I'm not assuming anything a car lot would or wouldn't do, but the thought crossed my mind since the fluid looked so good.

Good point about the winters and a cooler, I understand the fluid needs to be up to a specific temp before it goes into lockup for OD. I've heard conflicting stories about what that temp is though, some say 140° but I've also heard about 115° as well.

 

[TMoto]

Originally Posted By: Blokey
We had exactly the same hard shift issue with our '01 Olds Intrigue that also uses the 4T65E trans. We replaced the PCM and the problem never occurred again.

When I first started looking into this, I found the PCM to be named as the main culprit. The more I researched, I also found that it wasn't always the solution, and in some cases was a temporary fix. Replacing the PCM requires removing the side cover though, and that can be expensive due to labor. Mrs. TMoto was recently layed off from her job so things are kinda tight right now, especially with three kids in college.

Quote:
When I changed the filter the first time I replaced the pan with one with cooling tubes and a drain plug which made subsequent fluid changes a breeze.

That sounds interesting but it also sounds like it could be an expensive piece that only provides negligible benefit. Can you tell me where you got it, and how well it worked? Also, any ground clearance issues?

 

[sciphi]

No vacuum modulator on the 4T65. The 4T60 is the vacuum-modulated transmission.

The TransGo makes the shifts faster, not firmer. Besides the engine RPM's dropping very quickly after each upshift and downshifts being lightning-fast, I can't tell I ever installed the shift kit.

Minimum TCC lockup temperature on the 4T65 is 80*F. I've verified this with my ScanGauge many times in cold weather, waiting for the transmission to warm up so the TCC locks in 4th gear.

The hard shifts are caused by the pressure control solenoid failing. The PCM senses the shifts getting long and commands increased line pressure to actuate the shift. Eventually it's so bad the line pressure is maxed out, and you get harsh, banging shifts. The shift kit takes over for the failing PCS, and helps modulate the line pressure mechanically. This reduces the strain on the PCS, and reduces problems later on. It's why some rebuilders put the shift kit into their rebuilt 4T65's. It's good for their rebuild, and saves their customer money when their rebuilt transmission lasts longer than a transmission without the kit.

Dex-VI really isn't the fluid for a 4T65 transmission experiencing problems. Having used both Dex-VI and Maxlife ATFs in my Buick, the Maxlife has kept the shifting better than the Dex-VI was at the mileage on the fluid. I dumped my Dex-VI for Maxlife after ~12k miles on the Dex-VI since the shifting was getting rough again. So I ran Auto-RX for ~1500 miles, and did a cooler-line flush after installing the TransGo. After ~7k miles on the Maxlife ATF, the shifting is still fast and smooth. No slipping, either. I also installed a Magnefine for good measure, and have a stacked-plate B&M cooler that's disconnected every winter. As you can tell, this transmission is well looked after.

Your plan of ARX, the TransGo, and Maxlife ATF will work well. The hard shifts are most likely a failing solenoid, especially on the 1998-2003 versions of the 4T65.

Cost: Shift kit $65, ~12 quarts of Maxlife ATF (look at Wal-Mart) $60, ARX ~$30, filter kit (re-use the OEM gasket if not leaking!!!) $15, stacked-plate cooler $45. Total: ~$210

 

[TMoto]

Originally Posted By: eljefino
A shift kit generally makes firmer shifts anyway, which supposedly *save* wear and tear on the trans. It sounds like by default you are getting this behavior.

The faster shifts from the shift kit will feel firmer, which I don't mind from a slushbox anyway. I believe the transmission goes into a "max adapt" mode due to the longer shifts, thereby firming them up to save wear and tear, however I'm guessing if I ignore the problem it will get worse and eventually the shifts will become so hard that parts will begin to fail completely due to either the original problem or the hard shifts. That's just my guess though.

My first car when I turned 16 was a 1965 Impala SS 409 (thinly veiled brag

) that had the two speed Powerglide and it started to slip. Before I could get it fixed it failed one night, wouldn't shift, and I had to drive across town from my girlfriend's house in first gear. Sounded great with glass packs and the dual side exhaust. A friend helped me swap out the Powerglide, and that was my initiation into wrenching my own vehicles. I really don't want that to happen in this case. Shoulda kept that old beast, but I'm rambling now, so...

Quote:
Dex VI has a great rep but is thin, if your issue is temp/viscosity related it'll be worse. Maxlife is on the thick side. However, if your issue is temp affecting the solenoids (happens sometimes) the DexVI will be great.

Good points, I think I read somewhere on BITOG that this trans like a thicker fluid, which makes me lean towards the MaxLife.

 

[Steve S]

The firmer shifting adds more shock loading to minimally designed transmissions as most are, that is why the fail.

 

[Steve S]

TMoto , I can feel the pain!!

 

[TMoto]

Originally Posted By: sciphi
The TransGo makes the shifts faster, not firmer... [snip]

Thanks, this confirms a lot of what I've been reading elsewhere.

Quote:
Dex-VI really isn't the fluid for a 4T65 transmission experiencing problems... [snip]

This is exactly the recommendation I was looking for, coming from first-hand experience.

Quote:
Your plan of ARX, the TransGo, and Maxlife ATF will work well. The hard shifts are most likely a failing solenoid, especially on the 1998-2003 versions of the 4T65.

At this point this looks like the direction I'll take, I'll bump the thread when I get some results to post. One thing I've found around the net while looking for solutions to this problem is I'll find a post stating the issue, people reply with suggestions, and OP never returns to state the results if anything worked or not.

Quote:
Cost: Shift kit $65, ~12 quarts of Maxlife ATF (look at Wal-Mart) $60, ARX ~$30, filter kit (re-use the OEM gasket if not leaking!!!) $15, stacked-plate cooler $45. Total: ~$210

I was at Wal-Mart tonight and no Maxlife ATF. They don't even have Penz Platinum any more, which has been my oil of choice for the past few years, and was pleased to see it getting good reviews while perusing the oil forums here.

 

[sciphi]

Originally Posted By: Steve S
The firmer shifting adds more shock loading to minimally designed transmissions as most are, that is why the fail.


Yes, the factory maximum pressure settings will eventually kill the transmission. They also alert the owner to an issue.

The shift kit for a 4T65 takes over for damaged/broken electronics and helps mechanically set the line pressure. It does this by limiting travel in the shift accumulator pistons.The kit provides stiffer springs and spacers to prevent excessive travel that builds up the pressure. With the limited mobility and increased damping, the pressure is enough to actuate the shift. It's not ever high enough to make a hard shift. So instead of sustained high pressure, it's quicker and more consistent bursts of pressure coming down the lines. This completes the shifts much faster than the transmission's 0.5 second window for seeing the shift completed.

The effect of the shift kit is the "max adapt" code gets shut off since the transmission sees the shift getting completed in normal time and line pressure limits. So the transmission goes back to operating normally since it's sensing shift times and line pressures within its "normal" operating ranges. And the driver does not notice a banging shift before.

That's how the TransGo kit works for the 4T65. And why it's a good place to start for harsh shifting issues.

The more rural Wal-Marts may have Maxlife ATF. Advance and AutoZone should have it also. See if you can't use the discount codes for Advance on the ATF. It's not motor oil, they may let you...

 

[bmwtechguy]

Maxlife is a lower viscosity ATF in it's latest version. I cannot find a data sheet right now. Still a good fluid.

 

[sciphi]

Originally Posted By: bmwtechguy
Maxlife is a lower viscosity ATF in it's latest version. I cannot find a data sheet right now. Still a good fluid.


Yes, to meet the Dex-VI spec. It's still an excellent fluid, and I am using and recommend using it without reservation.

 

[wapacz]

Originally Posted By: TMoto
Originally Posted By: sciphi
The TransGo makes the shifts faster, not firmer... [snip]

Thanks, this confirms a lot of what I've been reading elsewhere.

Quote:
Dex-VI really isn't the fluid for a 4T65 transmission experiencing problems... [snip]

This is exactly the recommendation I was looking for, coming from first-hand experience.



At the same time i have read many posts in this forums of people running dex6 in the 4t65 and having nothing but good things to say about it. The current factory fill for this same transmission is dex6. Meaning new cars with this same transmission come straight from the factory with it.