1996 Suburban Tranny Weirdness

Ok all I purchased myself a 1996 suburban from a friend for cheap. The engine runs good and has new fuel injectors, cylinder heads, gaskets (cylinder head, intake gaskets, etc.) and is all tuned up with new plugs and wires, etc. 4 wheel drive, 5.7 liter engine, half ton. My problem is that when the car shifts into second gear, it will shift and then the rpms will shoot up, it will acclerate to 3rd gear eventually, but when it reaches higher speeds (over 35 MPH) it will jerk, like it is shifting in and out of overdrive or something. I realize a transmission rebuild is the most probable solution. However some people I have talked to (like my transmission shop) seem to think it could possibly be a sensor problem. Also, the person i bought this from had it at a friends house being worked on. He was the person who did the engine work and has been trying to figure out the supposed tranny problem. He was saying he messed with the catalytic converter, or some components related to it, and got it working much better. However as the man who did the work speaks spanish and i do not, i have not got any details (yet) on the work he did with the catalytic converter. The vehicle operates great in 1st gear (before it shifts into second), just like normal, shifts and drives in all gears, and also in reverse. I appreciate any comments or suggestions/ideas on the subject. Thanks!

My burb is doing the exact same thing and has been irritating me for months now. I cant seem to pinpoint the problem. The only code I can pull from it is an O2 low voltage on bank 1 & 2 sensor 1 and after clearing the codes the only way they come back is under heavy acceleration or when I am climbing a steep hill. I know the O2 sensors have alot to do with the ECM and drivetrain switching them into safe mode when there are any problems. This triggers the transmission to stay in third (AAMCO told me this) in order to get you home. Other than that the truck runs great except for the symptoms you posted about and the fact that I cant climb any steep hills without an almost complete loss of power and major shaking. Sorry I couldn't be that helpful on the cause of your problem but if you do find the solution to it PLEASE post back so I know what to do with mine.

Ok all I purchased myself a 1996 suburban from a friend for cheap. The engine runs good and has new fuel injectors, cylinder heads, gaskets (cylinder head, intake gaskets, etc.) and is all tuned up with new plugs and wires, etc. 4 wheel drive, 5.7 liter engine, half ton. My problem is that when the car shifts into second gear, it will shift and then the rpms will shoot up, it will acclerate to 3rd gear eventually, but when it reaches higher speeds (over 35 MPH) it will jerk, like it is shifting in and out of overdrive or something. I realize a transmission rebuild is the most probable solution. However some people I have talked to (like my transmission shop) seem to think it could possibly be a sensor problem. Also, the person i bought this from had it at a friends house being worked on. He was the person who did the engine work and has been trying to figure out the supposed tranny problem. He was saying he messed with the catalytic converter, or some components related to it, and got it working much better. However as the man who did the work speaks spanish and i do not, i have not got any details (yet) on the work he did with the catalytic converter. The vehicle operates great in 1st gear (before it shifts into second), just like normal, shifts and drives in all gears, and also in reverse. I appreciate any comments or suggestions/ideas on the subject. Thanks!


There is a brake band, inside the trasnmission, that must hold during 2nd and 4th gear operation. It sort of sounds like the 2/4 band is not holding well enough. Especially as you describe the way the motor revs while in 2nd gear. Usually, excessive 2/4 band clearance will effect OD operation first. Then as it gets worse/worn, 2nd gear developes problems. Hard to tell with out driving it though :)

Ok well there is some new news. I went and drove the thing, and the SES light is on. I noticed it kinda runs a little rough and when up to higher speeds it tends to miss occasionally. The only code i pulled from it was p1345. I believe that is crankshaft/camshaft sensor location? Something along those lines. Is this a timing problem? I took it into the tranny shop and they said it just needs a rebuild, which I was expecting anyway. However how much affect does engine timing have to do with the tranny? It seems that for the tranny to operate correctly it needs a properly functioning engine, however the tranny has 152,000 miles on it and is probably due for a rebuild. Any experience with code p1345? The engine has new plugs, wires, cap and rotor.

Codes should be address first for sure. P1345 CKP/CMP Correlation. Is usually a problem with the distributor. Sometimes, simply out of time because someone set timing wrong, or loose. One would have to moniter computer data with a graphing scanner, to see if the sensors are dropping out intermitantly. And set timing with scanner as needed.

This can effect shift schedual/timing. Not really make the trans slip. But if timing was really late then low engine power output can happen also. And with low power, alot of people can think thats a trans slipping

The tranny shop should have been able to tell you a little bit about what parts where failing inside of it. Because a transmission isn't "one part". Next time, after they drive it or diagnose, have them explain whats not working in it. Or don't give them the time of day. Its not that hard to explain the individual working parts inside the trans, if you know how it works :)

Ok i have some news to shed some light on the situation. I talked to the owner about when it started acting up, this happened EXACTLY after his mechanic friend fired it up for the first time after installing new cylinder heads, gaskets, etc. This also includes the transmission problems. He said the transmission was working perfect before he had his friend do the work. I am willing to bet something wasnt put back together correctly. However the big question is what that something would be. I will take the car into the deal to get the code taken care of hopefully soon. Any ideas on what the dealerships charge to hook up their handy scanner and time the engine? Also the man who did the work on the vehicle ended up messing with the exhaust system and cat. converter, which may also be causing problems, besides the obvious exhaust noise. Any ideas on what might not have been hooked up or installed right that would make the tranny inoperable? The work that was done was new cylinder heads, gaskets, new fuel injectors, intake gaskets, etc. Also one thing that bugs me is the radio turns on and off sporadically like there is a short in the wire. Also there is a clicking in the dash that is sporadic too and whatever that clicking is powers the speakers on and off, because i can hear the speaker "fuzz" or whatever you want to call it when the speakers get power but no signal. Any ideas are GREATLY appreciated. Thanks!

With all the parts off the top of the engine having been messed with. It sounds like something wasn't put together correct. It may take a few or many hours of diagnostic time to figure out what the last person in there messed up. It can be very difficult, or very easy, to find the problem a previous tech has installed into the vehicle that he worked on. Its just too hard to tell without being in front of the car. I would expect to spend no less than 3 hours diagnostic, to locate previous repair problems. And if its less? That will be a blessing.

I think you should try to find an independent repair shop, that can be recommended by some local friends, family or businesses. A shop that is excellent with electronics, diagnostics and stays up to date on latest technology. And can explain the fundamentals of the work he is doing for you. Your problem may be buried deep into the previous repairs. You need to expect that. Especially if the last owner had some "mechanic" do the work. Obviously, the mechanic wasn't qualified to diagnose his own repair work:) Thats the difference between a parts replacer and someone who understands theory of operation.

Yes, a dealer is usually good, the techs are good, the service writers and politics are a different story.

I would make sure the car is good before going on to the radio for now :)

Ok all i have some more new news. I twisted the distributor counter clockwise only a few degrees, and then started the truck. wow! It ran MUCH smoother. I unplugged the negative battery cable to reset the computer and bingo! the SES light is off. Would it be a good idea to get the distributor seated with a scanner or is it probably fine if the computer doesnt complain about it? The engine runs darn near perfect now except i would like to get the crappy autolite plugs out of it and put in some good AC-Delco's. Unfortunantly the transmission issue is still there HOWEVER the situation has changed a little. NO MORE jerking/transmission slipping behavior, it feels fine now. Transmission operates fine when the gear shift selector is in 2nd and 1st gear, and reverse. Overdrive and 3rd gear is a different story. As soon as the truck hits 20 MPH, (when the gear shift selector is in Overdrive or 3rd) the RPM's will still shoot up, and if you put your foot into it it will accelerate up to 30 MPH (with the RPM's above 3000) exactly when it hits 30 MPH the RPM's will go down to normal (just a hair above 2000) When the transmission shop looked at it, they said the 3/4 clutch was bad and it needed a rebuild. However their tech only drove it for a minute and a half around the block before giving me their diagnosis. Also if there was a bad 3/4 clutch wouldnt it be inoperable completely? Like completely neutral out after hitting 20 MPH instead of just revving but still accelerating? Also wouldnt it do the same thing when the gear shift lever is in 2nd and 1st? The truck goes into see a mechanic what was reccomended to me by a friend on friday, and we will see what the verdict is. Have any of you experienced any of these problems i just mentioned? Or any ideas? ANY help or ideas are very much appreciated. Thanks!

Update: Ok i took it into the mechanic and he set the distributor with his scanner, he recommended a transmission shop to take it into so off i went. They drove it and we found out a few things. Once it hits 20 MPH it shifts down to 1st, then after 30 MPH it shifts into either 2nd or 3rd. Did not shift into Overdrive. They said this rules out a bad 3/4 clutch. They suspected a solenoid at first but are not sure how to diagnose it without taking the pan off and putting a scanner on it. It is scheduled to go to the tranny shop on wednesday so I will keep you all updated for anyone interested.

Shift Pattern 1-2-1-3

Sounds like someone will have their work cut out for them :)

Make sure:

GM bulletin, #6671-03A. Ground Kit GM part #12167310 is in place in VCM.

The tranny shop should know what this is.

I m brand new to this and am looking for something on my 97 burb, but found ur thread interesting and wonder what the last wd was. Mine had some problems after i bought it (fortunately i bought a used warranty which covered all the repairs). i had to be quite persistent as the dealer was trying to put it off on other things which were not covered. what it turned out to be was a combination of a bad valve body and the sun gear (which had somewhat exploded). i was getting that big jerky shift like u. i found that when i came to a stop (or if i was rolling down hill off an exit, for ex, i wd shift to neutral and do this), turn truck off, count to 10 (like resetting computer, as i was getting a chk eng lite or something-its been a bit so i forgot), then start up, and the big jerk shift wd stop, until i hit the highway again. it made no sense but after paying the $100 copay (they tried to get me to pay for 3 visits but fortunately the mgr was really nice and realized they had not corrected the original prob), they replaced those to parts, along w/some seals, etc, and it was like new. unfortunately they never listened to me on the 4-wheel drive and i didnt follow thru well and tho i cant pinpoint it i feel like soemthing is not right w/that. but thats a diff tale.
anyways sorry for rambling but am interested in what the final wd was on ur tranny.

Sorry it has been so long on the reply, i havent seen a computer for a while. Well the transmission shop concluded that the 3/4 clutch is burned out. This will come to a total bill of $1995.99 plus tax, also i think i will opt for the extended warannty. I will have the tranny rebuilt. My tranny shop uses a few aftermarket parts, such as a trans-go shift kit, heavy duty valves, and there were a few more other things that i cant remember right now. The manager told me the 4l60E is a weak transmission in these trucks, and that the aftermarket/heavy duty parts they put in the rebuild will help bullet-proof it. Hopefully this is true, and the rebuild will last at least as long as the original (152,000). I'm not a huge fan of aftermarket but i think in this case it is worthwhile, am i correct? The price of the rebuild sounds pretty typical compared to other posts ive seen. Anyway i thought i would give you the final word. Hopefully the truck gets in the shop next week, i just need to get finances in order.

I jsut got on to look up some things on a tahoe i am working on and for my 97 suburban brakes when i saw ur tranny prob. I bought mine used fr a dealer and i must say that even tho the used warranty i bought was costly, the tranny repair paid for it.
my problem would started when i woulod be coming off the highway and after stopping at the exit, when it shifted fr 1-2, bam, it was a harsh harsh slam into gear. when i took it into the dealer the 1st time, they told me it was a sensor, but that for whatever reason, sensors were not covered under the warranty! i was a bit ticked. then they told that i had a coolant leak, and that was coming fr the intake manifold, but good news was it was covered, after paying the $100 co-pay (i forgot the term).
well, 2 things came out of that. 1) my coolant leak which i didnt notice before was still happening, and turned out to be the heater control valve, which i ended up replacing myself, and 2) after some experimenting, i figured if it was a sensor, and it seemed to shift ok when i first started up, when i wd exit fr highways, i wd put into neutral, turn off while coasting, count to 10, restart, and voila...it shifted ok.
well, at some point something went bad in the tranny, and it stopped shifting...i cant remember, like i had 1-2, or 3-4? anyway i took it in, and they said that the sun gear had exploded, that was covered. Now i had told the customer service guy all the details, incl the original problems, etc. Unfortunately he did not relay all that info to the mechanic. Well, after replacing the sun gear, i still had problems and brought it back (i dont think i even got down the road). This time i talked to the mechanic directly (having been a former mechanic until my back went out in 12/88...i should have just done that to start with...but i had never dealt w/dealers before on such things as i used to rebuild trannys etc but i dont have the equip for that so...), anyway when i told the mech all the stuff he said "boy, that sure would have been nice to know before when i had the tranny out. you have a bad valve body assembly, and i cd have done that all on the same ticket. but now i think they are going to charge u 2 copays..."
well, i was not a happy camper. they sd they would look into things and call the warranty company. bottom line is, they repaired it all, and didnt chg me anything...i think they saw that i was in there before and they didnt fix it. so since i was having the same problems and maybe the valve body might have been the initial problem all along...
needless to say i was pleasantly surprised after all the stories i had heard fr customers when i was a mechanic about dealers, and soem of my delaings with them when i sent customers to them for warranty work (i once had the AG office...this was back in WI where i am from and hope to get by next yr...call me about warranty work i sent a person over to the dealer to take care of...i told them it was not even a point of a manufacturer's warranty...it was a 5 yr emmissions control warranty mandated by the Feds...i told them they should know that...i guess the dealer was trying to make them pay for it...altho i must say this for dealerships (tho pls dont mistake this for condoning their cheating ways)...when it comes to warranty work, the manufacturers essentialy only reimburse them pennies on the dollar...in a sense. that is, you know what a labor rate manual is-gives u the time it should take to do each job on a given vehicle. well, the is a warranty rate which is insanely less than the normal rate. so say the rate manual (i think its called something else but it has been a long time) gives u 6 hrs on a Volvo heater core (yes...i think it was at least that...ever try to replace one? despite liking volvos, it was totally insane how they put their heater cores in...let alone trying to replace them). Well, the warranty rate might only be 2-4 hrs, and when u add that up over time that is a lto of money you lose out on, b/c you ar estill paying ur mechanic hourly but only getting 1/2 the money back. it still doesnt jsutify trying to get it out of the customers (beleive me, this was not an isolated incidence...its a game for them...u can imagine how many times they do this and the customer doesnt know or complain about it...that's the problem w/these stats about customer satisfaction the companies like to use...its based, or used to be based, kind of on a RPN (reverse polish notation...like some of the calculators) system. take 100 customers, and if no one complains then that means customer satisfaction. however, the real stats are that when customers are upset, with a dealership for instance, they dont go back. thus, there is no report of problems or complaints. great system.
anyway sorry for rambling on. i have ADHD and i caught ur problem there and hope the rebuild takes care of it.

I had this same problem with my 1996 suburban..rpm's kept going up and down at highway speeds....it went away after changing all of the universal joints