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99 Silverado transmission woes

jbrooks26 on Wed September 19, 2007 1:38 PM User is offline

Year: 1999
Make: Chevrolet
Model: Silverado LS Z-71
Engine Size: 5.3

Hey Guys,

My truck is presenting early signs of transmission wear I think. Here is the situation, when accelerating from a stop it feels as if the transmission is slipping occasionally. The engine will rev and then the tranny catches and away we go. This initial slip is the only time it happens and it does not do it at every stop. This is normal acceleration, not road racing by any means. My question is this, I have had a leaky output shaft seal no the transfer case for a few months now and I just haven't had the time to replace it. If the transfer case gets low, could it be causing this slip that I have described? Or am I looking at two separate issues here? Also, is there anything short of replacing the tranny that could be done to remedy this situation? Of course I will try to install my new seal on the transfer case asap. Any suggestions or ideas are very welcome and appreciated. Thanks,

Josh

mhamilton on Wed September 19, 2007 6:35 PM User is offlineView users profile

The transfer case should be just gears... no fluid coupling that would slip from that.

For trans problems, the best place to ask is on the BAT Auto Transmission Forum: http://www.batauto.com/Forums/ -- Transman will be able to give you a very accurate diagnosis.

jbrooks26 on Wed September 19, 2007 8:21 PM User is offline

Thank you, I have posted this there as well. Thanks for the info.

Josh

MrBillPro on Wed September 19, 2007 10:40 PM User is offlineView users profile

If the tranny is slipping trust me you will get a P1870 code and it will say the input rpm's are greater than the output rpm's been there done that 3 months ago on my 98 GMC 1500 had mine rebuilt $1400.00 later all is good.

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Don't take life seriously... Its not permanent.

jbrooks26 on Thu September 20, 2007 9:01 AM User is offline

Nope, I got a P0753, 1-2 Shift solenoid Elec. I have been reading and there can be several causes for this, however with it being so intermittent I tend to believe that it may just be a sticky solenoid. I have posted this over on BAT in the transmission forums, hopefully they can give me a few options. Thanks guys, I appreciate the help.

Josh

NickD on Thu September 20, 2007 9:06 AM User is offline

Quote
If the tranny is slipping trust me you will get a P1870 code and it will say the input rpm's are greater than the output rpm's been there done that 3 months ago on my 98 GMC 1500 had mine rebuilt $1400.00 later all is good.

Ha, that is your payback if you were dragging a 36' long camping trailer, seen a lot of these tiny SUV's hauling some pretty tall stuff at 75 mph+ on the interstate while listening to the groans of the AT when they pass me by.

What AT's have in common with AC's, in AC's can't put in a condenser large enough, in AT's can't put in a fluild cooler large enough either. With all this electronic crap added to vehicles, why can't they add a simple thermistor to the AT to warn the driver his box is running hot? Instead, many have eliminated the dip stick on the premise that you won't pour in the wrong kind of fluid, still can pour in the wrong kind of fluid, just a lot more difficult. And can still check the fluid level, if you don't mind fluid pouring in your face.

MrBillPro on Thu September 20, 2007 10:44 AM User is offlineView users profile

Quote
Originally posted by: NickD
Ha, that is your payback if you were dragging a 36' long camping trailer, seen a lot of these tiny SUV's hauling some pretty tall stuff at 75 mph+ on the interstate while listening to the groans of the AT when they pass me by.



Nick that is why I had him "my buddy" put all heavy duty clutches and drums back in mine. He showed me the factory drum and clutches and what they look like compared to the heavy duty ones there was no comparison in the metal at all, the drum weighed twice as much and was twice as thick, when my tranny shifts now into all gears and even overdrive yes you can feel it a little more but it drops in no messing around. He told me if I have "any" problem he felt so sure about his rebuild for the rest of the life of the truck just bring it back, but that extreme warranty may have a little to do with the fact I am his a/c man.

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Don't take life seriously... Its not permanent.

NickD on Thu September 20, 2007 11:24 AM User is offline

So for 1,400 bucks, did you just drop off your vehicle and pick it up? Sounded like a good price, especially since your buddy added all that good aftermarket stuff, and if you have 4WD, there is a lot of crap in the way just to get at the AT. But what about a better cooler, ha, my buddy only had a one word vocabulary, install a better "cooler", besides all those aftermarket goodies.

HECAT on Thu September 20, 2007 1:08 PM User is offline

Just hanging or adding an auxiliary oil cooler is a very common "old school" approach and may create more problems than good to some of the newer vehicles today.

Of course, there is a need to add more cooling capability when you are stressing the OEM cooling system beyond normal driving conditions such as towing, mountain roads, racing, etc. All the OEM’s recommend that if an auxiliary cooler is to be installed, it should be in the return line between the factory cooler and the transmission and not as a factory cooler eliminator.

Under normal driving conditions, the factory transmission oil cooler system has been engineered to be of the correct size. In conjunction with the engine cooling system, it will provide the optimum cooling balance to keep the transmission fluid at the manufacturer’s most preferred operating temperature.

As we make heat exchanger flushing tools to return the factory trans oil cooling system to OEM performance standards; we talk to technicians that have always preferred to just install an aftermarket air over oil unit in front of the radiator and completely bypass the factory cooler. A sarcastic opinion is that this is done because they understand the inefficiencies and poor engineering issues at the OEM level and can redesign or re-engineer the transmission oil cooling system better.

Remember that the old concept of removing the coolant system thermostat for better engine cooling did not work for every model. Some ran cooler, some had no change, and some overheated. The same issue is occurring with the blanket decision to install air over oil coolers. Some newer systems are now being monitored by the computer for an optimum operating temperature range; installing an air over cooler in this situation can fool the computer to see it as a problem and throw a code. Some it helps, some it hurts.



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HECAT: www.hecatinc.com You support the Forum when you consider www.ackits.com for your a/c parts.

FLUSHING TECHNICAL PAPER vs2.pdf 

NickD on Thu September 20, 2007 3:02 PM User is offline

Have heard, makes sense, and do add an additional cooler in the return line to the AT. A major problem, least for me, is to find which of the two lines is the return line. Logic dictates that after driving the vehicle in city traffic for a bit, the cooler of the two lines should be the return line. But the typical cooler is just a short piece of tubing in the radiator, and with the ETC method of switching on the cooling fans, only after the engine is just about ready to blow it's cork, do the cooling fans work. In this case, the radiator may actually be heating the AT fluid, and the return line will be hotter than the feed line.

Other method would be to disconnect one of the lines and have someone start the engine, but get ready for a hot AT fluid shower so you can tell which way the fluid is flowing. Can go crazy trying to find this basic information in an AT manual.

Speaking about flushing, just about any AT rebuilder that doesn't do the installation will scream at you to flush the cooling lines and cooler, and don't buy just blowing them out with an air hose. Some of these FWD vehicles just have about 3' of tubing including that short piece hidden in the radiator, hard to believe after blowing there would be enough stuff in there to wreck a rebuilt, but you better do it.

The torque converter is what really makes the heat in these things, that slippage converts mechanical energy into heat by compression with as high as a 3:1 slippage ratio when you first hit the gas, but nice when after robbing a bank to get away quick. Towing doesn't help either and in most AT's, do not get torque converter lockup in 3rd gear, and OD won't hack it.

Are these new AT's more robust than the older ones? Back then a quick check for both torque converter operation and full engine power, was to slam hard on the service brakes, parking brakes on with the wheels blocked, put it in gear with a tach connected and see if you can exceed a posted minimum rpm value, even hold it up to 30 seconds. They do not recommend that anymore, you will toast your AT. I feel the latest generation of AT's are not as quite as robust as the older ones for this reason.

MrBillPro on Thu September 20, 2007 3:32 PM User is offlineView users profile

Quote
Originally posted by: NickD
So for 1,400 bucks, did you just drop off your vehicle and pick it up? Sounded like a good price, especially since your buddy added all that good aftermarket stuff, and if you have 4WD, there is a lot of crap in the way just to get at the AT. But what about a better cooler, ha, my buddy only had a one word vocabulary, install a better "cooler", besides all those aftermarket goodies.

Nick I hung around talking to his 86 year old Dad that started the business back in the 40's my Mom has used these folks for 25 years and no not 4 wheel drive just two wheel drive. Yes $1400.00 was I thought also a good price, but when his a/c kills over at his home "or in his case his 3 a/c units" he will call me and I am sure he would rather take care of me now than pay me later my going rate, I know thats what he was thinking because his old Dad told me they normally charge $2200.00 for a rebuild like mine a heavy duty rebuild.

Speaking of oil cooler lines one of mine on my 99 Suburban is leaking "just a very little bit" I never pull anything with it I thought about just taking the oil cooler part off at the oil filter and the hoses and let it be, I did that a long time ago on an old Chevy pickup don't know why it would hurt anything even on these newer cars, but I may just replace the oil cooler lines there only $40.00 each and no big deal to change I see 1.5 hrs. tops.

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Don't take life seriously... Its not permanent.

bohica2xo on Thu September 20, 2007 3:59 PM User is offline

Saab had the right idea with the old 900's. When they added an automatic transmission, they put the heat exchanger in the lower radiator hose. It was a large cooler for a 2L vehicle, so the trans ran cool. If you were flogging the trans hard, the engine temp gauge would show the added heat load. The BW37 trans in those cars usually goes past 200k miles without an issue.

Just adding a heat exchanger is a good plan - that can go wrong. Any heat exchanger should be in series with the OEM unit - regardless of what the supplier says. Placment within the cooling package can be critical in newer cars too. Ford has been putting the oil (engine & trans) coolers between the A/C condensor and the radiator, so adding a cooler to the front of the evaporator could affect the A/C performance...

Automatic transmissions are precision assemblies. Plenty of cool, clean fluid is very important. Regular fluid changes at half the listed service interval can go a long way toward extending the transmission life.

B.

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"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

HECAT on Thu September 20, 2007 5:02 PM User is offline

Nick,

Seems like my web site is temporarily down for updates right now. If interested, when it is back up you can find an extensive list titled "Which line is the return line?" under "Trans FAQ's". Also take a look at "Coolers have teeth?" which is our answer to the fear marketing strategies of some of our competitors. This will show you the internal screen design of today's GM coolers; they make great filters for torque converter clutch materials. If you don't back flush out that flow restricting clutch material and metal debris from the previous failure you can overheat and or contaminate the new unit, you can see why your tranny guy says it must be done. Sounds mysteriously similar to our A/C flushing discussions, doesn't it.

B,

Great point about blocking A/C condenser air flow and the Ford factory air over oil unit you mentioned. In larger RWD models, it also includes P/S cooling and a trans thermal bypass valve to aid in rapid heat up to optimum trans temps. Ford recommends not to flush but to remove and disassemble (bolted stack plate design) to clean. But I am sure you already new that and could tell me more.



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HECAT: www.hecatinc.com You support the Forum when you consider www.ackits.com for your a/c parts.

FLUSHING TECHNICAL PAPER vs2.pdf 

bohica2xo on Thu September 20, 2007 6:19 PM User is offline

Hecat:

You mean the bolted stack lawn sprinkler? Cleaning one that way is fine, as long as you are not trying to make book labor...

Back in the dark ages of 1978 or so, ford was using the stacked plate BorgWarner cooler for aux. transmission cooling in the E & F series. BW went to some length to foolproof the install on an otherwise symetrical cooler. I had a BW engineer working with us on a project where we were using the same cooler. He was adamant about minimum flow rates, and foolproofing. Apparently they knew that the stamped grooves in the plates would trap crud if the flow rate allowed it to stay there. Reversing the flow on the cooler would bring out the worst in it as well. They accepted a certain volume of suspended particles in transmission oil, and did not want to start dropping them out in the cooler. We were advised to use 2ea 12 plate coolers in series, rather than a single large one.

I have since flushed many of these units, and find all sorts of interesting stuff on a reverse flush. I prefer to use tube & fin units for engine oil, based on those experiences.

I was lucky enough to lear a few things from a senior engineer @ Dunham-Bush before he left the game. Heat exchangers are a pain in the backside that you just can't skip.

B.

-------------------------
"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

HECAT on Fri September 21, 2007 8:47 AM User is offline

Quote
Originally posted by: bohica2xo
Hecat:

You mean the bolted stack lawn sprinkler? Cleaning one that way is fine, as long as you are not trying to make book labor...

Heat exchangers are a pain in the backside that you just can't skip.

Lawn Sprinkler...LOL

Heat exchangers...One man's pain in the backside is another man's challenge.

Have a great day.



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HECAT: www.hecatinc.com You support the Forum when you consider www.ackits.com for your a/c parts.

FLUSHING TECHNICAL PAPER vs2.pdf 

NickD on Sat September 22, 2007 8:13 PM User is offline

See that Transman suspects an electrical problem for Mr. Brooks, that reminded me of our problems with a GM truck and a 4L60, maybe it was a 4L61, who cares. Ignition switch, brake switch that engages the torque lockup, neutral safety switch, and the connector were all bare copper contacts and corroded. Took them all apart, cleaned and polished them, and coated with Lubriplate, lasted a long time without further problems, but was a job. Guy would think by replacing all that mechanical stuff with solenoids and a two buck microcontroller, these newer transmissions should be cheaper. Just the other way around.

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