4L60-E hard shift from first to second gear

letsbangout

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Hi all. I know this topic has been covered here and many other places on the Internet in depth.. but I'd like to explore a new angle to this if I may..

I have a 99 Yukon with the 4L60-E automatic transmission, and it shifts very hard from first to second. It's not even consistent, sometimes I can go extremely gentle on the throttle and make it shift acceptably, other times it's so firm it jolts the entire vehicle and makes a noticable sound as the whole interior vibrates. I took it to the dealership yesterday, and paid them $100 to simply drive it 2 miles and look at TSBs for the 2000 Yukon. Based on the TSB and their experience with a dozen other transmissions with the same problem, they're 90% sure it's the valve body. I guess the valve body gets worn or the solenoid gets worn and pumps too much fluid?

The obvious solution is to replace the valve body, which is like $440 in parts from Delco, or $100 to $200 if you buy from someone who remans and sells these on eBay. But rather than engaging in any of this, I'm curious if it's possible to simply tell the ECU to use a shorter PWM duration when pumping the fluid only in 1st to 2nd gear?

Specifically, this product:

http://www.autoanything.com/performance-chips/61A3637A0A0A2606874.aspx

purports to be able to control "shift firmness". What I'm curious about is whether it will let you go less firm than the factory setting. Or, perhaps there are other programmers out there that can do this?

Looking forward to comments from anyone who's used this solution to fix this problem, rather than opening the tranny, or from anyone who owns one of these or similar. Thanks!
 

bowtiefreak

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You may want to ask black bear about that....

I had this happen 8 years ago, same problem, same solution of a new valvebody
 

SunlitComet

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The wear will just continue and the programmer eventually won't change things enough.
Part# should be 24221161 for valvebody.
This is really the only permanent solution.

If you have not seen it your self hear is the tsb:


File In Section: 07 - Transmission/Transaxle

Bulletin No.: 01-07-30-023B

Date: March, 2002

TECHNICAL
Subject:
Harsh 1-2 Upshift, SES, MIL, or CEL Illuminated, DTC P1870 Set
(Replace Valve Body)

Models:
1996 Buick Roadmaster
1996 Cadillac Fleetwood
1999-2000 Cadillac Escalade
1996-2000 Chevrolet Camaro, Corvette
1996-2000 Pontiac Firebird
1996-2000 Chevrolet and GMC Light Duty Truck Models
1996-2000 Oldsmobile Bravada
with 4L60-E Automatic Transmission (RPO M30)
Built Prior to January 15, 2000 (Julian Date 0015)

This bulletin is being revised to update VIN Breakpoint Date information and revise the Parts Information table. Please discard Corporate Bulletin Number 01-07-30-023A (Section 07 - Transmission/Transaxle).

Condition

Some customers may comment on a harsh 1-2 upshift and the Check Engine Light or Service Engine Soon indicator is illuminated.

Diagnosis

Typically, these vehicles will have been driven more than 32,000 km (20,000 mi) before this condition occurs.

The scan tool may show a DTC P1870 set as a history code.

A harsh 1-2 shift or DTC P1870, caused by wear in the control valve body, may be difficult to duplicate when the transmission temperature is below 93°C (200°F).

Cause

The condition may be due to wear in the control valve body. This wear occurs in the bore that contains the TCC isolator and regulator valves, and results in poor, or no, TCC apply.

Important :
^ DTC P1870 is a type B code. The conditions for setting the P1870 DTC must occur on TWO CONSECUTIVE TRIPS (ignition cycles, with a drive cycle) before setting a P1870 history code.

^ When the conditions for setting DTC P1870 are met (first trip), the PCM commands maximum line pressure and harsh 1-2 shifts are the result.

^ This may result in a harsh 1-2 shift with no history code if the conditions for setting the DTC required for the second trip are not met, on two consecutive trips (Ignition cycles, with a drive cycle).

^ When the conditions for setting the DTC are met, on the second consecutive trip, a DTC P1870 is stored as a history code.

^ When the P1870 code is stored, the PCM will turn on the Service Engine Soon (SES), Check Engine Light (CEL), or Malfunction Indicator Lamp (MIL).

Correction

Install a control valve body with the revised TCC regulator and isolator valves. Refer to the Parts Information table below. These valves are used in all transmissions produced after January 15, 2000 (Julian Date 0015), and all of the service parts currently available through GMSPO contain revised TCC regulator and isolator valves.
Important : If all of the following conditions are true, it is not necessary to rebuild the transmission or to replace additional transmission components beyond the control valve body.

^ Transmission operation is normal before the transmission reaches operating temperature, or before DTC P1870 is set (no slips, flares, or missing gears).

^ The torque converter is not blue or overheated.

^ The transmission fluid is not burned or has no burned odor

^ The transmission fluid pan contains no abnormal debris (clutch material, bronze, brass, or metal fragments).
 

letsbangout

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You may want to ask black bear about that....

I had this happen 8 years ago, same problem, same solution of a new valvebody

Out of curiosity, how many miles did your tranny have on it when it developed this problem? And was it the high-temperature thing where it throws P1980 and occurs mostly after the tranny is very warm?

Mine, by contrast, happens at all times, both cold and hot, FYI.
 

bowtiefreak

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Mine was when it was hot. It happened with 40,000 miles on the truck. The next tranny lasted 100K till I replaced it with the new motor and it never had a problem....just did the whole new drivetrain.
 

letsbangout

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Mine was when it was hot. It happened with 40,000 miles on the truck. The next tranny lasted 100K till I replaced it with the new motor and it never had a problem....just did the whole new drivetrain.

Thanks for the reply, that's insightful. Everyone who seems to have this problem, from what I recall reading, has it happen at high temps after running for a long time or being on the highway, and it's characterized by overheated torque converters and perhaps gears with broken or bent teeth by way of the heat.

What's interesting is that I can't recall ever reading about anyone having this problem when their tranny is cold, like mine. I'm wondering what the long-term effects are of just letting it lock up hard, while going extremely gentle on the throttle. Another angle I'm exploring is the possibility that the problem could be exacerbated by bad emissions. By that, I mean, I averaged 13.3 MPG between a little city and a lot of highway driving. If the emissions systems were correct, I would think the mean between the EPA estimated city and highway for this truck (14/18 respectively) which would be 16 MPG (or higher!) should be expected. 13.3 is a far cry from 16.. and the reason I'm hot on this is because I read on another forum (maybe I have the URL saved on my laptop?) that someone else had this problem because of a clogged exhaust, and a new exhaust with new O2 sensors did the trick.
 

SunlitComet

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Your unit may be to far worn if you are sure it happens when cold. Letting it keep doing that will accelerate wear on other components. Not to mention maybe break a mount. That fact that your vehicle jolts or shakes that hard justifies shutting it down to it is repaired.
 

letsbangout

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Your unit may be to far worn if you are sure it happens when cold. Letting it keep doing that will accelerate wear on other components. Not to mention maybe break a mount. That fact that your vehicle jolts or shakes that hard justifies shutting it down to it is repaired.

Yeah I think you're right.. besides, that particular programmer only lets you go more firm, not less firm. So with that out of the way.. I suppose it's time to buy a valve body and find someone to install it. The guy I bought the truck from is a mechanic, owns his own shop, and I'm sure he's friendly with someone who will install my part.

I read on other forums that people who have done the valve body swap themselves (which I won't do because tranny work is voodoo to me), had good success in buying remanned units from eBay, like this one:

http://cgi.ebay.com/ebaymotors/G-M-...r_Truck_Parts_Accessories&hash=item1e5f3ba8d6

Do you suppose that's acceptable, or do I need the Delco part at the full $440-ish price? Also the dealership quoted me the repair with a new plate, do I need that as well?
 

cadillacmatt

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my escalade just started doing this if i turn it off for a min it works and i guess the transmission gets hot it starts again
 

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