4L60E BANG! during kickdown, now no 1st Gear

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Schurkey

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1997 1998 GMC Sonoma (Chevy S-10) 4.3L V6, 4WD, 4L60E

This is the vehicle that had a frozen battery and loose negative cable at the battery terminal. Parked since September-ish because I was told the alternator was defective. I put a battery in it a week ago, tightened the cables. No trans problems noted during that test-drive. Owner drove it ~50 miles today with no notable problems except a MIL illuminated.

Today I tested alternator, works great. Cleared a single code, for evaporative emissions, looked at gas cap, has damaged O-ring.

Decided to be "thorough"; took the truck for a test-drive. ~50 mph, stabbed the gas, trans kicked-down to a lower gear, and as it did--BANG! The whole truck convulsed. Now, not only do I not have first gear when in "Overdrive" or "Drive", but OD seems weak--slippy.

Reverse is good, and truck will move when shift lever is crammed down to "1" or "2", but no (first) gear engagement in "D" or "OD", so the truck doesn't move from a stop in those two positions. It drives reasonably normally if I start in 1 or 2, and shift up manually--although OD is questionable.

Using the scan tool to check--key on, engine not running--I can hear the solenoids click for 1-2, and 2-3 shift solenoids. No codes stored, and no shift adaptions post-test-drive--but I cleared the engine evaporative code before the test drive, so maybe that cleared whatever trans codes and shift adaptions might have been stored.

Fluid level is good, and not burned-looking but is "old" light-red not "cherry red".

Ideas on what I broke? Common problem?

Adding insult to injury, the alternator quit working sometime during this test-drive. I though maybe the "bang" was the serpentine belt breaking, but I wasn't that lucky.
 
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AuroraGirl

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1997 GMC Sonoma (Chevy S-10) 4.3L V6, 4WD, 4L60E

This is the vehicle that had a frozen battery and loose negative cable at the battery terminal. Parked since September-ish because I was told the alternator was defective. I put a battery in it a week ago, tightened the cables. No trans problems noted during that test-drive. Owner drove it ~50 miles today with no notable problems except a MIL illuminated.

Today I tested alternator, works great. Cleared a single code, for evaporative emissions, looked at gas cap, has damaged O-ring.

Decided to be "thorough"; took the truck for a test-drive. ~50 mph, stabbed the gas, trans kicked-down to a lower gear, and as it did--BANG! The whole truck convulsed. Now, not only do I not have first gear when in "Overdrive" or "Drive", but OD seems weak--slippy.

Reverse is good, and truck will move when shift lever is crammed down to "1" or "2", but no (first) gear engagement in "D" or "OD", so the truck doesn't move from a stop in those two positions. It drives reasonably normally if I start in 1 or 2, and shift up manually--although OD is questionable.

Using the scan tool to check--key on, engine not running--I can hear the solenoids click for 1-2, and 2-3 shift solenoids. No codes stored, and no shift adaptions post-test-drive--but I cleared the engine evaporative code before the test drive, so maybe that cleared whatever trans codes and shift adaptions might have been stored.

Fluid level is good, and not burned-looking but is "old" light-red not "cherry red".

Ideas on what I broke? Common problem?

Adding insult to injury, the alternator quit working sometime during this test-drive. I though maybe the "bang" was the serpentine belt breaking, but I wasn't that lucky.
At least you still have reverse. If you lost D/OD 1st gear then...

To my recollection, it sounds like an input sprag.

The overrunning clutches operate in manual 1, 2 but not in D/OD

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Bulletin No.: 08-07-30-027

Date: June 04, 2008

Subject:
No Movement When Transmission is Shifted to Drive or Third - Normal Operation When Shifted to Second, First or Reverse (Replace Forward Sprag Assembly)

Models:
1982 - 2005 GM Passenger Cars and Light Duty Trucks
2006 - 2007 Buick Rainier
2006 Cadillac Escalade, Escalade ESV, Escalade EXT
2006 Chevrolet SSR
2006 - 2008 Chevrolet Avalanche, Colorado, Express, Silverado Classic, Silverado, Suburban, Tahoe, TrailBlazer
2006 GMC Yukon Denali, Yukon Denali XL
2006 - 2008 GMC Canyon, Envoy, Savana, Sierra Classic, Sierra, Yukon, Yukon XL
2006 Pontiac GTO
2006 - 2007 HUMMER H2
2006 - 2008 HUMMER H3
2006 - 2008 Saab 9-7X

with 4L60(700r4), 4L60E, 4L65E or 4L70E Automatic Transmission (RPOs MD8, M30, M32, M33 or M70)

Condition

Some customers may comment that the vehicle has no movement when the transmission is shifted to DRIVE or THIRD position, but there is normal operation when it is shifted to SECOND, FIRST or REVERSE position.

Cause

This condition may be caused by a damaged forward sprag assembly (642).

Correction

When inspecting the sprag, it is important to test the sprag for proper operation by holding the outer race (644) with one hand while rotating the input sun gear (640) with the other hand. The sun gear should rotate only in the counterclockwise direction with the input sun gear facing upward. If the sprag rotates in both directions or will not rotate in either direction, the sprag elements should be inspected by removing one of the sprag assembly retaining rings (643). Refer to SI Unit Repair section for forward clutch sprag disassembly procedures.

If the sprag is found to be damaged, make repairs to the transmission as necessary. A new forward roller clutch sprag assembly is now available from GMSPO.
You must be registered for see images attach

If clutch debris is found, it is also very important to inspect the Pressure Control (PC) solenoid valve (377) fluid screens. Clean or replace the PC solenoid (377) as necessary. It is also important to flush and flow check the transmission oil cooler using J45096. Refer to SI Automatic Transmission Oil Cooler Flushing and Flow Test for the procedure.
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The notches above each sprag must point up as shown when assembled into the outer race.

Bearing Assembly, Input Sun Gear

Snap Ring, Overrun Clutch Hub Retaining

Hub, Overrun Clutch

Wear Plate, Sprag Assembly

Retainer and Race Assembly, Sprag

Forward Sprag Assembly

Retainer Rings, Sprag Assembly

Outer Race, Forward Clutch

Washer, Thrust (Input Carrier to Race)

The following information applies when this sprag is used in 1982-86 transmissions.

The new design sprag can be used on models 1982 through 1986, by replacing the entire assembly (637 - 644). Individual components are NOT interchangeable.

Important:
The wear plate (640) and input thrust washer (660) are not required with the new sprag. Use of the thrust washer and wear plate with the new sprag assembly will cause a misbuild (correct end play cannot be obtained)
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NickTransmissions

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1997 GMC Sonoma (Chevy S-10) 4.3L V6, 4WD, 4L60E

This is the vehicle that had a frozen battery and loose negative cable at the battery terminal. Parked since September-ish because I was told the alternator was defective. I put a battery in it a week ago, tightened the cables. No trans problems noted during that test-drive. Owner drove it ~50 miles today with no notable problems except a MIL illuminated.

Today I tested alternator, works great. Cleared a single code, for evaporative emissions, looked at gas cap, has damaged O-ring.

Decided to be "thorough"; took the truck for a test-drive. ~50 mph, stabbed the gas, trans kicked-down to a lower gear, and as it did--BANG! The whole truck convulsed. Now, not only do I not have first gear when in "Overdrive" or "Drive", but OD seems weak--slippy.

Reverse is good, and truck will move when shift lever is crammed down to "1" or "2", but no (first) gear engagement in "D" or "OD", so the truck doesn't move from a stop in those two positions. It drives reasonably normally if I start in 1 or 2, and shift up manually--although OD is questionable.

Using the scan tool to check--key on, engine not running--I can hear the solenoids click for 1-2, and 2-3 shift solenoids. No codes stored, and no shift adaptions post-test-drive--but I cleared the engine evaporative code before the test drive, so maybe that cleared whatever trans codes and shift adaptions might have been stored.

Fluid level is good, and not burned-looking but is "old" light-red not "cherry red".

Ideas on what I broke? Common problem?

Adding insult to injury, the alternator quit working sometime during this test-drive. I though maybe the "bang" was the serpentine belt breaking, but I wasn't that lucky.
Sounds like input sprag assembly to me, possibly coupled with front planet. Your low roller and rear gears seem to be working otherwise you wouldnt have any movement in manual low or 2.

Time to yank it out and tear it down. Drop the pan, look for kibbles and bits. If you dont see any, the problem may be confined to the input sprag which is holding in gears 1-3 when in D-manual low (low roller also holding in manual low). Your coast clutches are on in D3, 2 and manual low so you may have third gear in D3 and OD when manualy upshifting to Drive as the input sprag is overrunning in 4th (ie not holding/effective). Pressure test and inspect your input drum carefully for cracks on the clutch housing body - sometimes, if the sprag assembly fails catastrophically, the drum will fracture.

Input sprag failure is somewhat common. You'll need to replace the entire sprag gear assembly, not just the one way clutch element itself as the races are no longer trustworthy.
 

Schurkey

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THANKS, folks.

This thing is likely going to the local trans shop Monday. Too fookin' cold here to consider a D-I-Y project; and I'm not in the mood anyway.

That or the truck gets scrapped. Which would be something of a shame, in that it's probably the second-nicest vehicle they own.
 

Schurkey

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Bit the bullet, my favorite trans shop finished it today.

Yes, it rolled the input sprag. They added their usual TransGo valve body stuff, and an additional ground strap from trans to frame. That's part of their standard operating procedure; and I have no objections.

They replaced the Forward clutch sprag, the "Frt sprag assy", 3-4 clutches, a band, the torque converter, flushed the cooler, a bushing, a roller bearing, two solenoids, a "switch", the "master kit"...etc.

Required a new exhaust donut, and they cleaned the MAF sensor.

$2944.55, which is an easy thousand dollars less than my expectation. It's also less than they charged me for the 700 in my '88 which they rebuilt several years ago. That one had wiped-out planetaries.
 
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AuroraGirl

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Bit the bullet, my favorite trans shop finished it today.

Yes, it rolled the input sprag. They added their usual TransGo valve body stuff, and an additional ground strap from trans to frame. That's part of their standard operating procedure; and I have no objections.

They replaced the Forward clutch sprag, the "Frt sprag assy", 3-4 clutches, a band, the torque converter, flushed the cooler, a bushing, a roller bearing, two solenoids, a "switch", the "master kit"...etc.

Required a new exhaust donut, and they cleaned the MAF sensor.

$2944.55, which is an easy thousand dollars less than my expectation. It's also less than they charged me for the 700 in my '88 which they rebuilt several years ago. That one had wiped-out planetaries.
thanks for the update, the kinda helps seeing how much the going rate for that repair is. my 1996 has, to my knowledge, the same damage. Guess the used 1996 4l60e i have which had brown ATF is going in!! @NickTransmissions could you advise anything on that? I have a used 4l60e from a 96, so it matches what my truck is, and it says PWM on the pump cover. Is there any amount of opening up i can do as someone who hasnt been inside one before can do to see if its worth the time swapping in? And maybe replace anything able to be seen by dropping the pan? I ask because its sitting in the bed of my 1996 and I can lift the thing. So I could take it home and put it on a bench if need be.
 

NickTransmissions

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thanks for the update, the kinda helps seeing how much the going rate for that repair is. my 1996 has, to my knowledge, the same damage. Guess the used 1996 4l60e i have which had brown ATF is going in!! @NickTransmissions could you advise anything on that? I have a used 4l60e from a 96, so it matches what my truck is, and it says PWM on the pump cover. Is there any amount of opening up i can do as someone who hasnt been inside one before can do to see if its worth the time swapping in? And maybe replace anything able to be seen by dropping the pan? I ask because its sitting in the bed of my 1996 and I can lift the thing. So I could take it home and put it on a bench if need be.
Pop the pan off and look at what's on the bottom...Same thing I tell everyone else...If you see black clutch material, metal, lots sand-like matter (either silvery or bronze in color), it's more than likely no good. Brown fluid is not an encouraging sign....

Also, make sure your replacement trans is, in fact, a 1996 unit, not a 1995...The 95s have 'PWM' on the front of the pump but the selector shaft is the same length as a 700R4's or 1993-94 4L60E whereas the 1996 selector shafts are longer to accommodate the manual lever position sensor that's bolted to the case over the selector shaft. Also, the 1995s don't have the mounting provisions for the shift cable bracket where as 1996+ do.
 

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Pop the pan off and look at what's on the bottom...Same thing I tell everyone else...If you see black clutch material, metal, lots sand-like matter (either silvery or bronze in color), it's more than likely no good. Brown fluid is not an encouraging sign....

Also, make sure your replacement trans is, in fact, a 1996 unit, not a 1995...The 95s have 'PWM' on the front of the pump but the selector shaft is the same length as a 700R4's or 1993-94 4L60E whereas the 1996 selector shafts are longer to accommodate the manual lever position sensor that's bolted to the case over the selector shaft. Also, the 1995s don't have the mounting provisions for the shift cable bracket where as 1996+ do.
The trans does have a MLPS and it has the output speed sensor bracket on the tailshaft in the right spot, apparently a 1995 didnt have that in the same side (driver iirc?) I also confirmed by looking at its stamped code since the tag is no longer on the case. The brown was a slight exageration, you could see it was red. But more like what Dexron II looks like after 20k of normal use red not "this is ******" red. Obviously its not dexron II so there is that.. lol. I checked the fluid by removing dipstick tube and sticking my finger in it (it wasnt sealed on that well) which means it could also potentially be dirt contamination.
 

NickTransmissions

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The trans does have a MLPS and it has the output speed sensor bracket on the tailshaft in the right spot, apparently a 1995 didnt have that in the same side (driver iirc?) I also confirmed by looking at its stamped code since the tag is no longer on the case. The brown was a slight exageration, you could see it was red. But more like what Dexron II looks like after 20k of normal use red not "this is ******" red. Obviously its not dexron II so there is that.. lol. I checked the fluid by removing dipstick tube and sticking my finger in it (it wasnt sealed on that well) which means it could also potentially be dirt contamination.
Hope it works....
 
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