Transmission Slipping..(Was Shift Solenoids)

[joeb]

Solenoids are in valve body on bottom of 4t80e trans? And they are under side cover on a 4t65e trans instead? Why such a different parts layout for 2 similar trans? Or are they not that similar?

[Cadillac Jim]

I would have to haul out my GM Transmission Overhaul manuals to take a look, but I do believe that the 4T80E was an all-new design. The numerical designations are pretty generic - 4 gears, T for transverse, 80 for 8,000 pounds GVWR, and E for electronic (operated by the PCM instead of a vacuum modulator and hydraulics). The 4T65E is for FWD vehicles with a GVWR of 6,500 pounds and thus would be a physically different unit to fit under the hood and attach to the engines and half-shafts of smaller cars.

I don't think that all 4T80E transmissions are alike, either. For example, the transmission designation for all Northstars was 4T80E but I would wager that the 4.2 liter supercharged Northstar used in the V series used different torque converter, cooling and clutches, and perhaps much more.

[Texas Jim]

What transmission does my 2006 DTS have in it??

Is it a 4T65E or 4T80E ??

[Cadillac Jim]

Texas Jim - if it's a FWD Northstar, the designation is 4T80E. According to Wikipedia, it is.

http://en.wikipedia.org/wiki/GM_4T80-E_transmission

[Texas Jim]

Texas Jim - if it's a FWD Northstar, the designation is 4T80E. According to Wikipedia, it is.

http://en.wikipedia....-E_transmission

Thanks Jim,

That's what I thought, but wasn't totally sure.

[joeb]

found it. a 4t80 has them on bottom valve body. a 4t65 has them on side valve body. hundreds of threads at other websites. solenoids can fail with no codes. the electrical portion is ok but the body cracks/breaks so it appears ok to computer. or it can fail electrically. i have no codes. am in limp mode. speedo works. tach works. reverse is ok. nothing a replacement valve body wont fix.

[Cadillac Jim]

The "valve body" on the 4T80E doesn't move and other than several ball-bearing-type check valves it doesn't have valves, either - except for three solenoids that are operated by the PCM using PWM signals (fast on-off modulation like used in a house wiring dimmer switch). All you need are the solenoids. If it was my car, then once I had the valve body off, I would change all three solenoids.

[joeb]

i took off the side cover on a 4t65 this spring. was at junkyard and they had a pile of trans. found a 4t80 at bottom of pile but could not turn it over. my local boneyard has a 96 and 97 eldo i can play with. i am planning on practicing on those. the valve body on a 4t65 is prone to wear. perhaps a 4t80 VB is less prone? but the shift solenoid issue seems to be more common on the 4t80?

[BodybyFisher]

See this link, I posted check ball locations, not sure why you want to replace the valve body but the two shift solenoids are easily replaced. Shift solenoids were a problem at some point, but they redesigned or added a bracket to stop the body from cracking

http://caddyinfo.ipb...4;

[BodybyFisher]

Another really good link plenty of good info here on this

http://caddyinfo.ipbhost.com/index.php?showtopic=28472&st=0&p=144062&hl="check%20balls"entry144062

[joeb]

I read MAC's thread. "trans is acting up". Now that's an understatement. I did head gaskets, a/c system and now have trans issues?

[Cadillac Jim]

The Hydramatic transmissions that don't have an "E" at the end have multifunctional valve bodies and vacuum modulators that control the shifting. The function of the valve body and vacuum modulator is in the PCM and its sensors and shifting is controlled instead with three solenoids in the transmissions that do have an "E" at the end of their designation like the 4T80E.

Apparently the 4T65E works differently than the 4T80E in that one or more of the solenoids operates a valve body, instead of just a valve as in the 4T80E. The Wikipedia write-up on the 4T65E is here:

http://en.wikipedia....smission#4T65-E

The 4T80E stands alone as a distinct design, according to the Wikipedia article, although the writeup attributes the Turbo Hydramatic 125, a light-duty all-new design that first appeared in 1980. The Wikipedia page on the 4T80E is here:

http://en.wikipedia....-E_transmission

According to the Wikipedia article, the TCC design was changed from a viscous clutch to a hard clutch in 2005. So, not all 4T80E transmissions are identical, although all of them were used only on Northstar powertrains.

[joeb]

Took off VB on boneyard 96 eldo. Interesting. I see now how the solenoid clips are held. And how the casting blocks the removal of solenoids. Check balls have spherical pockets to seat in. Easy to keep track of them. Take off VB. take off case screws. Turn over and separate body halves and there u go.

[Cadillac Jim]

The transmissions on the Eldorado and Seville are interchangeable (at least for any given model year). The only thing to watch for is the final gear ratio, which is 3.11 for the VIN "Y" cars (base models) and 3.71 for the VIN "9" cars (STS and ETC), and that shouldn't be a consideration for internal parts. If you ever do get a transmission from a VIN "Y" car to replace yours, changing the differential is fairly simple because it us under the cover for the right half-shaft, and you can keep your differential from your original transmission.

[joeb]

VB I took part had the filter/ bracket. I took off bolts and bracket feel off. I didn't even see it till it feel on floor. I did not look for small filter as I was not sure where it was. I did find some more pics that show it between solenoids. My car is may,96 build so I assume it has redesigned parts. But do the solenoids still fail in 96+ cars? It seems more common on 92-95 cars but many later cars seem to have issues too. What else would cause a newer car to go into limp mode?

[Cadillac Jim]

If the car is actually in limp mode, that is a PCM operating mode, so there will be an OBD code that tells why. If there are no codes, then a mechanical problem with the solenoids that is not detected by the PCM might be the problem.

Exactly what do you mean by "limp mode?" Precisely what is happening that you need to fix? For example, is it shifting hard, holding onto gears too long, not using low gear, etc.

[KHE]

VB I took part had the filter/ bracket. I took off bolts and bracket feel off. I didn't even see it till it feel on floor. I did not look for small filter as I was not sure where it was. I did find some more pics that show it between solenoids. My car is may,96 build so I assume it has redesigned parts. But do the solenoids still fail in 96+ cars? It seems more common on 92-95 cars but many later cars seem to have issues too. What else would cause a newer car to go into limp mode?

I'm surprised a junkyard would let you disassemble a transaxle that you were not going to purchase.

The solenoid failures are more prone in the '93-'95 cars. I think the solenoid support bracket was used starting with the 1996 model year.

[joeb]

was at folks on tuesday doing stuff. 100 miles away. going home the trans decided to act up. i think it has 1 gear. does not seem to shift. is it 1st gear or 2nd? almost all threads say it is 2nd gear in limp mode. reverse is ok. car does move. so i left it and took dads spare car home. i am looking for info before i tear into it. can a 96 obd2 car access trans codes from the dash or is it a shop code reader required?

[Cadillac Jim]

If it won't shift at all, it's not in limp mode. When anything is wrong with the suspension, ABS, or TCS, the PCM will skip low gear on startup, but pressing hard on the accelerator at 10 or 15 mph will downshift into low - and in any case there will be an OBD code that tells why low gear was disabled.

There is a limp-home mode that is actuated when the engine temperature gets nearly high enough to damage the engine; in that mode, half the cylinders are disabled and pump air to cool the engine, and the order of disabled cylinders is changed every second or two to distribute the cooling effect. The engine has about 50 hp in the limp-home mode. I wouldn't use it unless personal safety was involved.

If it's stuck in 1st gear, the engine will rev at any significant speed; think over 4000 rpm at 30 mph. If it's stuck in 2nd gear, it will lose its snap off the line but will drive normally, with engine revs a little high but not too much unless you get over 40 mph or so. If it's stuck in 3rd gear, takeoff will be very sluggish but it will drive normally at light throttle. I've never heard of a 4T80E being stuck in 4th gear, but if that happens it will have a hard time getting off from a dead start, have little pep at speeds below 50 mph, but drive normally at light throttle at highway speeds. If you didn't drive the car but just parked it, as I would be tempted to do to avoid the possibility of damaging the transmission further, you may not have enough experience with the problem to tell which gear it was stuck in.

If you have no codes and the transmission is stuck in any gear, you almost certainly do have a mechanical problem with the shift solenoids, as you know. There are three solenoids, two for shifting and one to operate the TCC; I would replace all three if I went to the trouble and expense to get at even just one of them, just to be sure that I never had to do that again. You are already making sure that you have the bracket for the 1996 and later transmissions to support the solenoids.

I am surprised that you don't have an OBD code because mechanical problems with the solenoids usually cause open or short circuits in them, which will throw a code.

[joeb]

I have reverse and 1 gear? Seems to hit 3500 rpm to hit 35mph? VB has 2 shift solenoids and 5 port manifold pressure and range sensor. All other sensors are under side cover which is very hard to reach. I would consider changing shift solenoids but not other sensor. But I need to drop pan first.

[KHE]

can a 96 obd2 car access trans codes from the dash or is it a shop code reader required?

Simultaneously press and hold the OFF and PASSENGER WARMER side of the rocker and the codes will be displayed on the information center.

[Texas Jim]

I have reverse and 1 gear? Seems to hit 3500 rpm to hit 35mph? VB has 2 shift solenoids and 5 port manifold pressure and range sensor. All other sensors are under side cover which is very hard to reach. I would consider changing shift solenoids but not other sensor. But I need to drop pan first.

3500 RPM at 35 mph = being in 1st gear.

[Cadillac Jim]

It does look like the PCM can't shift, other than PRN1, so one of the shift solenoids is inoperative. Let's see what the OBD codes say, and hope for an external electrical problem.

[joeb]

can anyone ID my new ride?

went to boneyard again. found a 04 deville with subframe on ground and motor gone. but trans was there.

turned it over and pulled pan. pretty clean job with trans on side.

seems it has a different design manifold pressure switch.

[winterset]

When in diagnostic mode with "Off and Warmer", the HVAC reports via symbols what the trans is doing. you can try this out by entering diagnostic mode, and pressing the brake pedal. I believe it reports that as a signal to turn of Overdrive. The shop manual has a table of each symbol, and what is means what signal is being sent or received from the trans. We used to have this table online , but I have not seen it in years on this site. I guess since the trans is so well built, there really is not a demand for it.