Is anyone else experiencing this with the transgo kit under almost none to light throttle? It didn't do this before the shift kit. Now it has a loud clunk with the 2-3 shift, but only under none to very light throttle. It's a 2001 Silverado with the 4L60E.

 

Looking at your signature, I see you have the billet servos. IMHO, the billet servos are overkill, and the 2nd gear piston acts as the 3rd gear accumulator, which may be the cause of your clunk.

 

I was thinking that, but it did not do that when I had the billets in before the shift kit. Under acceleration it doesn't do this. It's only when i'm coasting downhill and it shifts from 2-3.

 

I installed my transgo and corvette servo today and I have the exact same clunk in the 2-3 under light throttle. Has anyone figured out if this is normal after a shift kit install.

Thanks,
-Brandon

 

I'm suspecting it may be the slip yoke. There is a tech service bulletin out about driveline clunk related to this, but most complaints have been from the 1-2 shift. I have noticed mine doing this on the 1-2 sometimes also, only when i'm rolling down a hill and the transmission shifts with no resistance. I think the shift kit makes this clunk more apparent since it is shifting harder and faster. I'm going to try greasing the slip yoke and see if it gets better. There is a nickel-plated replacement yoke available but i'm sure it costs a pretty penny from the stealership. They priced me one (but had no idea if it was the updated one) for $227

 

It looks like we have the "2-3 upshift or 3-2 Downshift Clunk noise"

I called Lyndon (Westers) and he said he would be able to reprogram my tune in order to correct this. I will let you know once I receive my ECM.

A/T - 2-3 Upshift or 3-2 Downshift Clunk Explanation

File In Section: 07 - Transmission/Transaxle

Bulletin No.: 01-07-30-042A

Date: December, 2002

INFORMATION

Subject:
Information on 2-3 Upshift or 3-2 Downshift Clunk Noise

Models:
2003 and Prior Light Duty Trucks
with 4L60E or 4L65E Automatic Transmission (RPOs M30, M32)

This bulletin is being revised to add the 2003 model year as well as information about 3-2 downshift Please discard Corporate Bulletin Number 01-07-30-042 (Section 07 - Transmission/Transaxle).

Some vehicles may exhibit a clunk noise that can be heard on a 2-3 upshift or a 3-2 downshift.

During a 2-3 upshift, the 2-4 band is released and the 3-4 clutch is applied. The timing of this shift can cause a momentary torque reversal of the output shaft that results in a clunk noise. This same torque reversal can also occur on a 3-2 downshift when the 3-4 clutch is released and the 2-4 band applied. This condition may be worse on a 4-wheel drive vehicle due to the additional tolerances in the transfer case.

This is a normal condition. No repairs should be attempted.

 

Gotta love GM for saying everything is normal!! FYI there is a nickel-plated slip yoke available for around $225 at the stealership that is supposed to help stop this also. Here's the tech service bulletin (it says during taking off or stopping, but i'm sure it applies to shifting as well)......

Clunk, Bump or Squawk when Vehicle Comes to Complete Stop or Accelerating from Complete Stop (Replace Rear Drive Shaft Nickel-Plated Slip Yoke )
1999-2002 Chevrolet and GMC Extended Cab Short Box Pickup Models (Silverado and Sierra)

with 4L60-E (RPO M30) or 4L80-E (RPO MT1) Automatic Transmission and Automatic 4WD (RPO NP8)

Condition
Some customers may comment on a clunk, bump or squawk noise when the vehicle comes to a stop or when accelerating from a complete stop.

Cause
A slip/stick condition between the transfer case output shaft and the drive shaft slip yoke may cause this condition.

Correction
Replace the rear drive shaft slip yoke with a new nickel plated slip yoke, P/N 12477702 (1500 Series) or 12477704 (2500 Series). Follow the service procedure below.

Raise the vehicle on a hoist. Refer to Lifting and Jacking the Vehicle in General Information (SI2000 Document ID # 349918).
Reference mark the propeller shaft to the pinion flange connection.

Important
Do not pound on the propeller shaft yoke ears. Never pry or place any tool between a yoke and a universal joint.


Remove the bolts and the yoke retainers from the pinion flange.
Slide the propeller shaft forward and out of the rear pinion flange.
Lower the rear of the propeller shaft and pull the drive shaft out of the transfer case.

Notice
Never clamp propeller shaft tubing in a vise. Clamping could dent or deform the tube causing an imbalance or unsafe condition. Always clamp on one of the yokes and support the shaft horizontally. Avoid damaging the slip yoke sealing surface. Nicks may damage the bushing or cut the lip seal.


Support the propeller shaft in a line horizontal with the table of a press.

Important
Remove the front slip yoke and the universal joint together. The new nickel plated slip yoke comes with a new universal joint.


Disassemble the snap rings by p inching the ends together with a pair of pliers.
If the ring does not readily snap out of the groove in the yoke, tap the end of the cup lightly in order to relieve the pressure from the ring.



Place the universal joint so that the lower ear of the yoke is supported on a 30 mm (1-1/8 in) hex head socket or a 27 mm (1-1/16 in) socket.



Place the J 9522-3 on the open horizontal bearing cups. Press the lower bearing cup out of the yoke ear.
If you do not completely remove the bearing cup, lift the cross and insert the J 9522-5 between the seal and the bearing cup you are removing. Continue pressing the bearing cup out of the yoke.
Rotate the propeller shaft . Press the opposite bearing cup out of the drive shaft yoke.
Remove and discard the slip yoke and universal joint.
Inspect the retaining ring grooves for dirt, corrosion, or pieces of the old ring.
Inspect the bearing cup bores for burrs or imperfections.
Clean the retaining ring grooves. Corrosion, dirt, rust, or pieces of the old retaining ring may prevent the bearing cups from pressing into place or prevent the bearing retainers from properly seating.
Install the new nickel-plated slip yoke and universal joint, P/N 12477702 (1500 Series) or P/N 12477704 (2500 Series).
Remove the bearing cups from the universal joint.



Assemble one bearing cup part way into one side of the yoke. Turn the yoke ear toward the bottom.
Assemble the cross into the yoke so that the trunnion seats freely into the bearing cup.



With the trunnion seated in the bearing cup, press the bearing cup into the yoke until the bearing cup is flush with the yoke ear.
Install the opposite bearing cup part way into the yoke ear.
Ensure that the trunnions start straight and true into both bearing cups.
Press the opposite bearing cup into the yoke ear while working the cross all the time in order to inspect for free unbinding movement of the trunnions in the bearing cups.

Important
If there seems to be a hang up or binding, stop pressing. Inspect the needle bearings for misalignment in the bearing cup


Press the bearing cup into the yoke until the bearing cup retainer groove is visible over the top of the bearing cup.
Assemble the bearing retainer in the retainer groove.
Continue pressing until both retainers can be snapped into place.



If the retainer is difficult to seat, the yoke can be sprung slightly with a firm blow from a soft-faced dead blow hammer.
It may be necessary to lubricate the snap ring with a slight amount of chassis grease so that the snap ring seats in the bearing cup groove.
Install the slip yoke onto the output shaft in the transfer case.
Align the reference marks on the pinion flange and the propeller shaft.
Install the yoke retainers and bolts. Tighten
Tighten the yoke retainer bolts to 25 N·m(19 lb ft).

Lower the vehic le.
Parts Information
Part Number
Description
Qty

12477702
Yoke Asm., Prop Shf Slip (w/Ujt) (Nickel Plated) (1500 Series)
1

12477704
Yoke Asm., Prop Shf Slip (w/Ujt) (Nickel Plated) (2500 Series)
1


Parts are expected to be available from GMSPO October 15, 2001.

Warranty Information
For vehicles repaired under warranty, use:

Labor Operation
Description
Labor Time

F0060
Slip Joint, Propeller Shaft - Replace
0.6 hr



GM bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer". They are written to inform these technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a job properly and safely. If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or tha t your vehicle will have that condition. See your GM dealer for information on whether your vehicle may benefit from the information. WE SUPPORT VOLUNTARY TECHNICIAN CERTIFICATION

 

I went to the dealership today and they don't belive that replacing the slip yoke will correct the 2-3 shift clunk. They said that normally the slip yoke will correct a clunk from a dead stop or when you come to a stop. Let me know if you try and replace the slip yoke, for now I'm going to wait and see what Lyndon can do and see if that corrects my clunk.

-Brandon

 

Reprogram.....should do that anyway after a trans go shift kit.

 

I have a similar-sounding "clunk-clunk" on my 2-3,
with no shift kit but modified trans params. But it
feels like it's more in the rear end; odd thing is that
it seems not to be there on the 1-2 or 3-4.

Unfortunately I do not see anything that offers
fine-grained control of the release / apply trans
sequencing, just shift time and pressure and points.

What sort of programming do you think would affect
the "clunkage"?

 

If it were constant on take offs or at least every few take offs and associated with the 2-3 shift Id say its the slip yoke, bc the 3 Ford super duties we have do that when the slip yoke isnt greased enough. But since this happens MAINLY on the 2-3 shift, it sounds like an internal problem, like the bulletin says, with the band and the clutch pak. You may be able to lessen the problem with tuning the shift sequence, but i believe the only real fix would to be upgrade the 2-3 clutch pak. But thats just what I would recommend from seeing some of the things I have with the 4L60E and its 'TYPICAL' problems! Best of luck, and let us know what happens. JP A.R.D.

 

I've got a beefed up 4l60 in my Z-28 and it clunks bad on the 1-2 shift. New tranny mount didn't fix it and torque arm is tight. Just started after tranny was beefed up. Multiple mechanics can't figure it out and said "maybe" it's the exhaust.

 

IMO it's the servo banging around in the case. Added line pressure will cause this, so just a shift kit or just changing line pressure will make it worse, some transmissions do it stock.
On the servo there are lugs that contact each other and cause the clunk noise, they are there to act as stops. I've seen servos out of transmissions with bad clunking shifts and these lugs are a bit more beat up but not to the point that it's of any worry at all, to me anyway.

The reason some vehicles do it and some don't is because one of line pressure, also because the band adjustment is not very critical, vehicles with tighter bands clunk less. At least in my builds I tend to shim the band on the tight side and don't have much of a problem with noise.
There is a big window for factory band adjustment specs so a lot end up on the loose side. Since travel is somewhat long it usually doesn't cause shift problems.