Lost 4th Gear; Code 28 and 58; 4L60E

[Supercharged111]

Accessible from the outside of the case--the 2--4 band servo assembly is the big, round, breast-looking thing just under the cooler tube ports. On some vehicles, you don't need to upset the trans mount, there's clearance between trans and trans tunnel for access. Other vehicles have tighter clearance, so the back of the trans has to be lowered, or you need a full bucket of harsh language.

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Servo upgrades are extremely popular--everyone and their brother has put a "Corvette Servo" in their 700/4L60/60E. That servo is for 2nd gear. There's also a big aftermarket servo for 4th gear. And, of course, folks sell a complete servo assembly with hot-rod parts for both 2nd and 4th gear.

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When my 4L60E case cracked, I lost 4th gear. I left the truck in 3rd all the way to the interstate where a hill greeted me as I merged. After the hill, I dropped the shifter into OD and nothing happened. I figured the rest of my drive was gonna be 1st and 3rd gear, but when I got off the highway I found I had 1-2-3, but the shifting was a bit off. At this point I was just praying it'd get me home and it did. The case cracked up by the servo, so I wrote the whole thing off and put in a 4L80E. Since your transmission stays full, I doubt the case is cracked, but wouldn't doubt some shenanigans down in the servo.

 

[Steve A]

My ATRA books say that 4L60Es with a KCD code (5.7L, 4WD) or at least some of them came from the factory with the "Corvette" 2-4 servo. Might want to check it out before laying money out for a new 2-4 servo.

 

[tayto]

Yes, towing with the pre-1996 trucks in D is generally a no-no.

My father's 1995 K1500 had a GM sticker on the driver's door that said, basically, "Don't tow in D".

The issue is the pre-1996 ECU doesn't properly interpret the operating conditions which exist under a load when in "D" (such as towing in overdrive) and may not lock up the torque converter; if so, the heat issues I mentioned in my prior post ensue. Not Good.

One can tow in D, but it's up to the driver to monitor the TCC and, if it's running unlocked, take remedial action... which is to shift into 3rd as it facilitates TCC lockup (for reasons I won't try to explain).

It has nothing to do with "pre-1996" or the ECU. when the shifter is in manual "D" position the 4L60E applys the overrun clutches but does not apply the overun clutches in 1st or 2nd gear. If you manually shift from 1st to 2nd to 3rd, the overruns will be applied in each gear. So if you DO want to tow in D, you need to manually shift through the gears. Sonnax makes a valve to fix this. FWIW, the 700R4 never had this problem.

Pretty sure the sticker would have said not to tow in OD.

Heavy Duty 2-3 Shift Valve - 77754-41

Improve input sprag & forward clutch durability. Critical upgrade for heavy-duty & performance vehicles. Easy install. 4L60-E, 4L65-E, 4L70-E. Part # 77754-41

www.sonnax.com

 

[1998_K1500_Sub]

It has nothing to do with "pre-1996" or the ECU.

Yes, it does. See my original post which you quoted.

 

[tayto]

Your post makes no sense, 3rd gear is "D". some calibrations had 3rd gear lockup and some did not. I upgraded a 92 GMC to a '7427 PCM from a 94/95 and the new calibration had lockup in 3rd. with that being said most calibrations that will lock up in 3rd will ONLY do it if you are in the manual 3rd position AKA D.

 

[1998_K1500_Sub]

Your post makes no sense, 3rd gear is "D". some calibrations had 3rd gear lockup and some did not. I upgraded a 92 GMC to a '7427 PCM from a 94/95 and the new calibration had lockup in 3rd. with that being said most calibrations that will lock up in 3rd will ONLY do it if you are in the manual 3rd position AKA D.

On the 1998 cluster "D" is 4th. I believe it's the same in 1995, since AFIAK the clusters are interchangeable.

The context of my post may not have made that clear.

 

[tayto]

it actually has an O around the D sometimes written as (D) meaning OD. Up until 95 the gear selector would read: (D) D 2 1. every 80s Gm car or truck I've ever owned, worked on or been in has it written this way.

 

[1998_K1500_Sub]

it actually has an O around the D sometimes written as (D) meaning OD. Up until 95 the gear selector would read: (D) D 2 1. every 80s Gm car or truck I've ever owned, worked on or been in has it written this way.

Your point is valid: My post didn't respect the difference in the earlier years prior to 1995. I should post a clarification or update my original.

Thanks

(edited on Feb2) I've since update my earlier post to reflect differences in pre-1996 vehicles.

 

[1500z71]

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[1500z71]

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