marthyh

Hi all the way from Holland.Need some advice.

Just got a 1998 Z28 and I find that it shifts quite hard(firm) from 1st to 2nd gear.
It is a real push in the back when cruising at traffic speed.Not really comfortable.

When I really step on it ,the shifts up is so hard that the back tends to break-out.Even with asr...

Is this normal ?

Or can I do something about it ?

For the rest I love it!!!Just have it for 10 Hours.

Many thanks

Martin

5_02ls1

iTrader: (20)

sounds like a shift kit or someones upped line pressure via a tune or an hpp3 or other programmer.....mine does that on the 2-3 shift...lol1-2 is a smokeshow...lol

marthyh

Which programmer you'd recommend to correct?

Already have made acces to obd with pcmscan.

Starion

iTrader: (5)

How many miles does it have on it? Mine had 76k and it shifted hard like you're describing when I got it. A tranny flush with new fluid took care of it. If you see no mods at all on the car then I would think there's less of a chance it has a shift kit.

WS6NIGHTMARE

iTrader: (7)

If it has a shift kit, all you can do about it is take it out. Flush it anyway just so you know where you stand on maintenance.

marthyh

It is completely stock,as far as I can see,difficult to get performance parts over here, with 74k KM (46k Mi).

So clean ATF ,what type and how to flush?

zzz28

check the trans mount mine did the same. it use to feel like a hard shift then after about a year it got worse and worse. my trans mount was in 2 pieces so id check for cracks in the trans mount.

staringback05

iTrader: (8)

check and see if the tranny's ever been rebuilt they might have slipped a trans go in there....if so you cant change hardware with a tuner in the way you want to...

also like stated check the tranny mount....and fluid levels

angel71rs

Other thing it can be is the infamous P1870 getting ready to set. Wear in the valve body for the valve that controls the TCC pressure causes slippage. Computer ups the pressure to try to compensate, one result being harder shifts. Eventually ends up setting P1870 when slippage becomes excessive. If P1870 does set, and you let it go for too long, can burn up TCC in torque converter requiring it's replacement. TransGo shift kit has a special valve they say fixes/prevents this from happening. That's one of the reasons I installed the TransGo SK as soon as I bought my Z. More info:

TSB # 01-07-30-023A
Harsh 1-2 Upshift, SES, MIL, or CEL Illuminated, DTC P1870 Set (Replace Valve Body)
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, 1999 (Julian Date 9015)
This bulletin is being revised to update the Parts Information.

Please discard Corporate Bulletin Number 01-07-30-023 (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. These valves are used in all transmissions produced after January 15, 1999 (Julian Date 9015), 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

SamhainZ28

iTrader: (28)

i had the same problem when i bought my 2000 z28, the guy before me removed the engine control fuse, located in the fuse box under the hood. The fuse controlled all of the o2 sensor heaters and the MAF sensor. it also controlled something in the transmission, my car would shift hard as hell on 1-2 like i had a shift kit, (which is what the guy said it was) after i replaced the fuse the car shifted perfectly without a problem. start there first before you drop the pan to see whats going on.

nasty z

My car does the same thing. I'm going to change the trans fluid this week, and hopefully it will stop. If it doesn't how bad is it to drive on the situation stated above? Any idea how much to fix?

Starion

iTrader: (5)

One interesting note in this thread is that each of us who have/had hard shifting all have a 1998. Maybe coincidence, or possibly it's more common with this particular year.

I had a BG flush done, but I don't know whether that's available in Holland. If you search on trans flushing you'll hear tons of differing opinions on whether it's good or bad. Since your mileage is low I personally wouldn't hesitate to flush it. With 46k on the clock, it's highly likely that it's still the original fluid.

Fresh fluid made a HUGE difference in shift quality with my car. Everybody loves firm shifts at WOT, but not necessarily at part throttle.

If I'm in your shoes, it's a good maintenance item at the very least so you know when it was last done. I would bet money that it will fix your shift quality issues. When you do it, make sure you insist on replacing the fluid with Dexron 3, non-synthetic ATF.

Some people just drop the pan, change the filter, and refill. If you go that route keep in mind that you're only changing like 1/3 of the total fluid. The tranny holds something like 15+quarts.

Congratulations on your new toy.

marthyh

Thanks very much all ;gives me something to go on.
great help ,
will have the car in the shop next week and let you know what happens,
Cheers

loodaman37

yea mines a 98 too and its been doin the same thing, only hard on 1-2 shift at barely any throttle and it gets me every time; feels like someone giving u a hard push from behind. I guess ill change the tranny fluid and see what happens gl with urs

RPM WS6

iTrader: (3)

Moving to Auto Trans section....

defcon(ls)1

iTrader: (1)

I also get the same with my 1998 T/A with 29,500 miles. The part-throttle shifts (both cold and warm) have a distinct lumpy nature from 1-2. 2-3 and 3-4 are fine. Also 1-2, 2-3 (didn't try 3-4) are excellent at WOT with crisp barking of the tires in 1-2. I did a fluid change (however not a flush) but no improvement.

marthyh

Did a fluid change 300mi ago now,the oil was deteriorated with black residue under in the pan.(no flush).No large metal particles...
Right after this refreshment, not much change in shift quality.

Must say gradualy gets better now.Only 1of 5 1-2 shifts is rough.
Want to change fluid again soon,good or not?

Also notice some play in the driveline at shiftpoints,what can that be or how to find out?

SteveC

I have a Transgo shift kit (#3 washer), coupled with a Superior Billet "Super 2-4 servo", and my 01 Z28 shifts very hard and crisp from 1st to 2nd.

The firmer the shift, the less slipage, I know why my setup shifts this hard, you should find out why yours does too. If there is a shift kit or aftermarket servo, all is well, if not, there maybe an underlining problem. Slipage equates to heat, and transmission wear, my digital trans temp guage tells me that all is well.

SteveC

defcon(ls)1

iTrader: (1)

Well I just did a trans flush (31k miles on entire car) and used I believe 14 quarts of Mobil 1 Synthetic ATF and it fixed it for sure.

ChocoTaco369

TEXTBOOK DIRTY MAF SENSOR!

Go to the autoparts store and get a can of MAF cleaner. I bet your MAF is dirty. When your MAF sensor gets dirty, it causes the transmission's line pressure to go through the roof and causes harsh shifts. This can lead to burnt clutches, so do this maintenance ASAP.

I'm willing to bet it's not a shift kit OR an aftermarket tune, but a simple dirty MAF sensor.