1993 Suburban Shudder

Here I am posting again. This site is extremely addicting. 93' 350 5.7 liter, automatic transmission, 4X4. When driving around 40 MPH +, maintaining a consistent speed, I feel the car kind of shudder, or pulse. Then when I let off the gas pedal I feel a distict shudder, worse sometimes than other times. This has always been the case since I have owned it (1.5 years) and running seafoam through it eliminated the shudder while driving at lower speeds (5-30 MPH). Is this some type of drive line problem? A rear-end problem? Transmission problem? My transmission shifts fine except for a semi-frequent (50% of the time) hard shift from 1st to 2nd. Shift is smoother if i let up on the gas before it shifts. Also acceleration is kinda sluggish in 1st gear as opposed to the rest. Like I said these things have always happened since i have owned the thing, hasnt got any better or worse. I am just wondering if any of you have had the same type of problems. Thanks for looking, and replies are very much appreciated.

~Suburban Freak~

1993 Suburban, 5.7 liter 350, auto, 4X4
Firetruck red, glossy black fender flares, yeah it's a head turner
deepest sounding stock exhaust i've ever heard
friends call to cruise the streets, or to help them get unstuck!

I have the exact same problem with my 93 burb, around 35-40 mph the engine just pulsates at a consistant speed and just like yours it kinda coughs on decel.

I added sea foam and that helped for about 20 mins then it started doing it again, I changed the plugs and that helped but again it stated acting up, I have no idea what it is, Im not going to go out and buy a crap load of parts just to find out what the deal is but if you find out let me know, good luck.

It is possible that this is TCC (Torque Converter Clutch) lockup issues with the 4L60E tranny. The TCC Apply Valve or TCC Regulator Valve can wear in the valve body and the Torque Converter Lockup causes the shudder.

//2000CAYukon

Hmm...makes sense to me. And I'm assuming to eliminate it I would need to buy a new torque converter? Does this situation of a possible worn out valve increase the chance of ruining my transmission or drivetrain? I don't want to spend money i don't have right away but if it is slowly ruining my transmission then it should be taken care of. Thanks for the reply this has been driving me nuts.

Hmm...makes sense to me. And I'm assuming to eliminate it I would need to buy a new torque converter? Does this situation of a possible worn out valve increase the chance of ruining my transmission or drivetrain? I don't want to spend money i don't have right away but if it is slowly ruining my transmission then it should be taken care of. Thanks for the reply this has been driving me nuts.

This is a fairly common issue with the Valve Body, not the Torque Converter itself. The tranny does not have to be removed to repair.

The pan is dropped and the valve body is removed and then repaired.

//2000CAYukon

As said valve body is one of the main problems.

Check engine tune up also. The engine has to be running good for the transmission to work good.

Next service the transmission filter and fluid.

I am not much on additives but in the TCC shudder case on that year a bottle of Lube-Gard {red} transmission additive helps a lot of them.

But stay away from strong chemical or other additives.
Good luck MT.

Wow you guys thanks for the info it's really helpful. I've read a little bit about the 4L60E transmission and its problems and the valve body is mentioned more than once. I suppose this is an expensive repair? Maybe I'll stop by my transmission shop and ask them about it. Also I will service the tranny and filter, and add some lube-gard. Also, would the harsh 1st to 2nd gear shift be something screwy with the valve bodies? Shifts fine through all other gears. Also 1st gear seems a little sluggish to me. Sometimes it even feels like its shifting late but that might just be a pshycological thing :screwy: Anywho i really appreciate all the info and ill keep you posted on what happens.

Harsh 1-2 may be valve body acumlator servo pistons and springs and sometimes spacer plate or even transmission weak.

The valve body repair is more labor than parts.
Good Luck. MT
www.sonnax.com
info@sonnax.com

1993Suburban - Does your truck shift out of overdrive alot while going up hills on the highway? even small hills? Mine is constantly in and out of OD on the highway and was wondering if the above info would relate to mine as well.

Well this morning I bought Lube-Gard transmission protectant. Poured the whole bottle down the filler tube as it directs in the instructions. Wow is all i can really say. The first thing i noticed right off was actual peppy-ness while accelerating, something that seldom happens with the burb. Second, I could hardly feel it shift into 2nd, which is again, something that seldom happens while driving the burb. Much much smoother shifting, and absolutely no pulsations. When i let off the gas pedal there is not so much as a hiccup. I have driven it all over town today running some errands and performance continues to improve. I suppose i lucked out, i was half expecting my tranny to go out or act weird. So far so good and hopefully it stays that way.

Well this morning I bought Lube-Gard transmission protectant. Poured the whole bottle down the filler tube as it directs in the instructions. Wow is all i can really say. The first thing i noticed right off was actual peppy-ness while accelerating, something that seldom happens with the burb. Second, I could hardly feel it shift into 2nd, which is again, something that seldom happens while driving the burb. Much much smoother shifting, and absolutely no pulsations. When i let off the gas pedal there is not so much as a hiccup. I have driven it all over town today running some errands and performance continues to improve. I suppose i lucked out, i was half expecting my tranny to go out or act weird. So far so good and hopefully it stays that way.

Glad to hear it helped it and all is well.
I would still drop the pan and put a new transmission filter in it.
Good luck
MT

1993Suburban - Does your truck shift out of overdrive alot while going up hills on the highway? even small hills? Mine is constantly in and out of OD on the highway and was wondering if the above info would relate to mine as well.

His problem was a TCC clutch shudder.
Yours is a kicking in and out problem.
Is it actually droping out of OD or just the lockup droping out.
The lockup drops or changes RPM 200-300 and a gear change changes rpm 500-600 rpm.
When yours drops down shift to no 3 gear and see if you can feel a change or if it changes rpm any.

Shifting down or lock up droping out can be caused by engine running problem or weak power.
And possiable worn valve body or eveen pressure switches on valve body.
Check you engine running up to par first.
Cat stopped up or tps sensor and engine miss and fuel and air filters and fuel pressure.
Check for any transmission and engine codes.
Has transmission ever been serviced?
How is the fluid and fluid level?
MT

I had that same issue with stuttering, then with power problems. Went through the gamet of possible fixes, cat converter, fuel filter, EGR, turned out to be my mapping sensor! Just a $60 fix. Runns GREAT now! Power restored, and no stu-stu-stuttering! Run a check on that before you invest in too much

Good info, but this a 14 year old inactive thread.

:grinyes: Yeah, I saw that after I posted that! But figured id leave it in case someone else has that problem.. newbee to the forum, hope it doesnt show!! Ha!

Your good, no issue.

[quote] Yeah, I saw that after I posted that! But figured id leave it in case someone else has that problem.. new bee to the forum, hope it doesn't show!! Ha! [quote] Maf seal breaksdown on old GM engines. the Map sensor voltage is 1.2 volts dc at idle RPM .