Hi, this is my first post. I have a ’95, 4x4, 4dr, automatic transmission, Blazer, with 138k miles. The problem I’m having is the following; When I’m cruising around 50-55, the trans lunges. The trans is shifting properly through all the gears from 1st to 4th, but it feels as if it wants to shift into OD but it doesn’t. The tach shows that the revs are fluctuating and the speedometer also fluctuates. If I place the shift selector on the “D” instead of the “OD” it doesn’t do the fluctuating. But the revs stay high and the fuel economy suffers greatly. The fuel pump assembly was replaced due to a rusted broken fitting. I’ve checked the fuel pressure, and it’s as is supposed to be, I have installed new spark plugs and wires, and have replaced the fuel filter (the old filter was clean) hoping to make this go away. The injector system was replaced about a year ago as it had a broken fuel injector hose. The trans fluid is at its proper level. I believe the problem is with the transmission. Is there a relay that controls the converter? If so, where is this relay located? Pictures of the location will help greatly. Is there a schematic of this electrical system? Can someone help by printing said schematic and showing it on this page? I have a 1999 automatic trans I took off a ‘99 Chevy SS S10 with 66k miles due to a broken shell. Will any of the parts of this transmission fit the 95 blazer trans? Any help from you guys is well needed. I’ve been reading this forum for quite a while and have searched for trans problems, and have read almost all the back posts searching to see if anyone has had this problem previously and no one has. At least I didn’t find any post that did. One came close to having the same problem and a relay controlling the converter was mentioned. This is why I’m curious about the relay. Thanks in advance and sorry for the lengthy post.

 

This sounds like TCC shudder to me... There is a TC solenoid that controls the lockup of the TC... I'd have to do some digging to find more information than that... Let me see what I can find. Hopefully Hanr3 will jump in with some insight.

 

Welcome to the site.

Like swart said, could be just a slipping torque converter lock up. What controls it, your puter controls it. Granted the puter gets info from various sensors, like TPS, VSS, brake switch, temp sensor, and MAP sensor. None of which are attached to the tranny, except the VSS.

Could it be a tranny problem, yep, however, lets make sure we rule out the engine first.
Get your MAP sensor tested. Make sure your vacuum lines are not leaking. The torque converter will lock up once the computer gets the signal from the MAP sensor that the vacuum is just right. The acuum will change with engine rpms. A leak in the vacuum system will prevent the torque converter from locking up, or moving into and out of lock up.

Even though you may not have a CEL (check engine light) on, go to autozone and have them check to see if any codes have been set.

Make sure your tranny has the proper amount of tranny fluid in it. Check it with the engine running after 20 minutes of driving. Park on a flat surface, leave the engine running, and check both sides of the dipstick, wipe, and check again. Make sure your within spec on the dipstick. If not add as needed. If you see fluid on the dipstick but are low, add 1/2 bottle at a time and check it again. Drive it first. Make sure it goes through all gears. then stop and check. Do this as many times as it take to get the proper amount of tranny fluid in it.

When was the last time you had the tranny fluid changed? How many miles?

'97 and '00 4L60E tranny share many similar parts. All of the clutch packs will interchange, and most of the internal parts with a few exceptions. The exceptions are parts that must be matched sets, so if you change one of them you must change all of them. There is one noticable difference between the '97 and '00 trannies. The '97 has the bellhousing as part of the tranny case, while the '00 the bellhousing is seperate and removeable. The removeable bellhousing must be removed before you install the pump, otherwise you will ruin the pump rubber o-ring in the process.

The last thing it could be is a worn out torque converter, although you don't mention any of the other signs for that. That is why I think your problem lies in the engine (a sensor) or low tranny fluid. Post up until we get this resolved.

 

One more thing. well two more things. Where I type '97, change that to '95. It still applies.

Lastly,
The tranny has 4 forward gears, 1, 2, 3, and 4th gear or commonly referred to as overdrive. 4th gear and ovverdrive are the same thing. Please don't confuse torque converter lock up with a gear. It is something completely different. The torque converter can lock up in 3rd and 4th gears, and on some of the newer trannies 2nd gear. Since you seem to be having the problems with it in 4th gear, I suspect a vacuum leak, MAP sensor, or TPS. If it was the torque converter lock up, it should do the same thing in 3rd gear.

Do you have a tach? If not, do this. Get up to speed on an open road. Radio off, windows rolled up so you can hear the engine. You should hear it drop in rpms through each gear, and finally when the torque converter locks up. When you think you have torque converter lock up while in 4th gear, lightly tap the brakes. This will instantly unlock the torque converter and th engine rpms should go up a couple hundred rpms. You will see it on the tach, and you should be albe to hear it in the engine.

Do this test as well, again up to speed on the open raod (no cars around you). Manuall shift through the gears, from 1st to 4th. Then back down again.

Post up what you find out.

 

Greetings. First, thanks for the welcome. And thanks for your quick replies. I really appreciate your help. This thing has been bugging me for quite a while. Your suggestions are great and I will follow them. Ref the trans fluid, I’ve checked the trans fluid constantly since I first noticed the problem and have maintained the level. Two months ago I changed the 3 way vacuum valve at the transmission because it was sucking up trans fluid. The fluid was accumulating at the vacuum tank and inflating my vacuum hoses. The comp system was last checked about a month ago and no codes were present. Tomorrow I’m taking it to the tech again to have another run with his computer. I will keep you abreast of what I find. Question, if the MAP sensor is bad, won’t it show as a fault in the codes? Also where is the VSS located?
Sorry for the delay in answering, but I was a little busy today. You know one of those days were every jump should be a skip but turns into a hurdle. Anyway, all things worked out for the best. Now, I can spend more time on the blazer problem. Again, thanks for your help.
[sm=icon_cheers.gif]

 

No, you may not get a fualt code with a dirty sensor. I think you need to clean your MAP sensor and replace your vacuum lines. The vacuum system is one system and runs to many places. The vacuum ball is only one of them, it also runs to your MAP sensor, and heat-a/c controls. Pull your MAP sensor out and clean it. I would also replace all the vacuum lines with new ones. Tranny fluid in the hoses will attract and hold any dirt that gets into the hoses (read you will fight this problem for a long time).

The VSS is located on the tranny (2wdr) or t-case (4wdr). '87 and prior it is located on teh back of the speedometer, in the dash.

 

Hola. Greetings. Today I did a couple of checks as you suggested. On my way to the tech I did the shifting through the gears both auto and manually. All shifts were good, at 4th, when I tapped the brake the rpm did go up. The surging happens at 50 –55 mph and the rpm fluctuate from 15k to 17k. The surging occurs when it’s in 4th. If I manually down shift to 3rd from 4th the surging goes away but the rpm stay high. The surging is more pronounced when going uphill or when under load. At the tech the readings from the sensors were negative. There was one historic code-misfire of 1st cylinder-, which is why I changed the spark plugs and the cables last weekend. Tomorrow I’m checking all the vacuum hoses for any leaks. I’ve done this in the past, when I replaced the 3 way vacuum valve at the transmission. I’ll do it again to make sure there are no leaks. Question ref the VSS, what does it look like, do you have a picture? Does it have 3 vacuum hoses connected to it? If it does this is what I replaced a couple of months ago. I will replace all the other vacuum hoses as soon as I can. For today this is all I have. Tomorrow I will remove the MAP and clean it out. I will keep you informed as I make any checks that will help in getting rid of this problem. [sm=smiley20.gif]

 

OK what your discribing by the surging sounds like the torque converter is locking in and unlocking for some reason. Teh 200rpm jump indicates its unlocking. Could be as simple as a dirty MAP sensor, or it could be as bad as a failing torque converter. Clean it first and see how that goes. Since the surging is more pronounced uphill, or underload I suspect it is operating normally. When you give her more gas to climb the hill, or pull the load the torque converter should unlock, adn if you keep pushing the gas peddle it should downshift into 3rd gear. Give that a try and see if that happens. Now when your crusiing on flat ground and no load, does it surge? If this problem just started, as in it didn't used to happen, we need to look at other facotrs, ie air filter, spark plug gap, rotor etc.

I found a pic that might help.
Clcik here for pic

In this pic the VSS is electronic. That means the reluctor and gear are located inside the t-case and the only thing coming from it is two wires. Look in the top of the pic, notice where the long output shaft of the t-case is? See the black wiring harness where hte long part connects to a smaller part which connects to teh main part of the t-case? (wish I could put an arrow on it for you) That harness is the VSS harness. Look on the bottom half of the pic, see the 3hose connector, and see the black wiring harness next to it. That black harness is for the push button shifting of this t-case.

 

Greetings. I checked out the MAP sensor and it wasn’t clogged up. It did have a little carbon around the little hole that goes into the manifold, but I looked into this orifice and could see that it was clean. When you said to clean the MAP this is the place that had to be cleaned, right? Another thing, while driving and going up hill with a load, if I step on the gas the trans does down shift into third and it stops surging. The surging occurs on flat ground as well. This problem did not start just recently it’s an on going thing. Which is making me crazy. I haven’t changed the vacuum hoses yet. Before I do I’m going to check all of them to make sure none are plugged or leaking, also I want to measure how many feet I’m going to need. I didn’t do this today as I was checking out the MAP. Also I was installing an updated sound system in the Blazer. Reference the picture for the VSS, I see the sensors, and appreciate you posting the picture. Thanks. Anyway, I’m beginning to believe that the problem lies with the vacuum. I’ve been looking for a schematic on how the vacuum hoses are supposed to go in the system and have not found any. I have a Chilton manual and it only shows the routing of the emission hoses. The vacuum problem is of course a suspicion on my part, but it’s about the only thing that needs to really be checked. Question, would any of the sensors on the engine cause this if they were malfunctioning? If so, which would be the culprit? If I’m too inquisitive I’m really sorry, but you seem to have a handle on the workings of this vehicle. And as I’ve read through the posts on the forum, you are the one that answers most of the questions having to do with problems of this vehicle. I don’t mean to place a burden on you and I really appreciate your patience and help. Thanks.

 

There should be a vacuum diagram in the engine compartment, unless it is too faded to read. I also think Autozones website has them. Look in the repair section. Swart might also be able to posst up a vacuum diagram for you.

Your doing fine. I am about out of things to check though. I hope swart can jump in here and tell you more about the MAP sensor, like how to clean it, and how to test it.


Post up what you find out on the hoses. You don't need to replace all of them, just the ones that are stiff, brittle, show signs of swelling or cracking.

I know this is going to sound strange, and I am not entirely why it fixed the problem. However on my sons Ranger he was also having a surging problem, a surging problem just like yours. On his truck we found that if he runs at least 89 octane gas the surging problem goes away. Since we discovered that, he has been running 89 octane gas and has not had any more surging problems. His was doing the same as yours, exactly the same as yours. Give it a shot, run a couple tank fulls through and se what happens.