GM 700-R4 questions.....

Alan Roehrich · 08-05-2010, 12:19 PM

Thanks Rob. I never can seem to remember it all. I always forget some of the stuff I should remember, no matter how much I remember.

Rob Petrie E395 · 08-05-2010, 04:29 PM

Quote:

Originally Posted by Alan Roehrich

Thanks Rob. I never can seem to remember it all. I always forget some of the stuff I should remember, no matter how much I remember.

Hey I forget more than I can remember LOL! I just work on alot of trucks being in farm country and if you could see some of the stuff that comes into my shop you would know why I remember the older stuff better than the newer stuff. Some days I would kill to do a oil change on a nice new one.

ss3011 · 08-05-2010, 08:01 PM

This is a cable operated transmission, and shifts based on road speed and throttle cable position. As an engine loses power, when it is old and worn out, or out of tune, you have to step on the throttle more to get the vehicle down the road. Sometimes we have seen this happen if the catalytic converter gets plugged. Many times these old vehicles are so weak, the throttle position needs to be opened so high that all the upshifts feel delayed, the fourth gear shift is at a higher mile per hour then you are going. Does the transmission shift into overdrive if you backoff the throttle but downshifts back into 3rd if you step back into throttle , to maintain road speed ? Same could be happening with the TCC. There is a throttle position load release for TCC. So once the TP is higher than a calibrated number, say 30% then TCC will not come on.

Greg Reimer 7376 · 08-06-2010, 10:44 PM

I have a 91 Chevy Silverado 1500 pickup,350,TBI,700R4, and it did that. Brake light switch worn out. It kept the TCC and the cruise control from working. Replaced it, truck is fixed. Try that first.

Greg Reimer 7376 · 08-07-2010, 11:12 PM

I just had another thought regarding the issue your S-10 Blazer has. It seems that the computer PROM in the GM computer is probably expecting to see a drop in engine RPM after 50 or so MPH,and it doesn't see it. If the torque converter clutch is not applying,it's in a mode of less than 1:1. It's a pretty loose converter, so the discrepancy is being seen between the vehicle speed sensor(which also runs the speedometer), and the engine speed sensor, which is picked up probably by the tach signal in the distributor. The person who suggested that you test the torque converter clutch apply solenoid for proper operation made a good suggestion.The diagnostic trouble code(DTC) would be caused by that excessive engine RPM at that road speed and that seems to all make sense. Identify the DTC, and that should make a proper diagnosis probable. Since you indicated that it was an intermittant condition,then got worse, it's probably something like that. If the trans fluid is all brown,smelly, and full of big particles, then that was probably the result.Good luck with your project!!

ss wannabee · 08-08-2010, 08:20 PM

Thanks for all the responses...Unfortunately, work and family issues took up most of my spare time this weekend and had little time to investigate. I DID manage to get a hold of a GM service manual for the vehicle...and it has diagnostic troubleshooting charts which
mentioned most of the stuff you've said. Looks like I can electrically test the solenoid and
brake switch through the ALDL connector with a test light...and I'll do so. BTW, the Blazer
doesn't have antilock brakes...I think they came a year or two later. The trans fluid seems ok in color and smell on the stick...What I might do is just CHANGE the solenoid anyway along with the filter and fluid. I bought the piece some months ago...but I'll check the resistance Rob..just to see...I saw that the GM manual says the sol. is "junk" if it measures LESS than 20 ohms,,,,maybe the working "spec" is 20-30 ohms? Alan...you mentioned a "stacked shift" situation...YES this vehicle has done that...ALSO intermittently for the last 10 years or so....sometimes loading up the vehicle so badly that I'm forced to downshift. That's one reason why I'm leaning towards solenoid replacement. The Blazer is driven in the overdrive position..it works fine...no need for manual shift.

ss wannabee · 08-08-2010, 08:45 PM

Forgot to mention but the tech at the garage next to work has been too busy to scan the vehicle. So I tried the "old-school" method with a paper clip and counted the flashes. What I got was Code 32...which is an EGR system malfunction. I watched through 3 or 4 cycles to make sure it was the only code....It was....NOT sure if the scan tool could "find" more...but it can give engine temp,TPS voltage, and other stuff that might be relevant. I'll still try to have that done. I don't think this is related to the trans problems but.....I want to point out that this code "sets" ONLY when I attempt to drive the Blazer on the highway...and the engine rpm is over 3,000...heading to 4,000 when the overdive doesn't work. When the o.d. is working properly, I don't think the engine speed goes over 3 grand...and I highway drive at the speed limit...I "baby" the vehicle...Whoever mentioned "easing" up on the throttle to get overdrive...I've tried that recently...NO results lately...although it has worked in the past.... I don't think the converter is clogged...perhaps the opposite....NOW it's time to try some things.....Thanks again, Guys!

08-05-2010, 12:19 PM	#1
Alan Roehrich Veteran Member Join Date: May 2006 Location: Murfreesboro TN Posts: 5,113 Likes: 1,571 Liked 1,821 Times in 413 Posts	Re: GM 700-R4 questions..... Thanks Rob. I never can seem to remember it all. I always forget some of the stuff I should remember, no matter how much I remember. __________________ Alan Roehrich 212A G/S

08-05-2010, 08:01 PM	#3
ss3011 Senior Member Join Date: Feb 2002 Location: Southeast Michigan Posts: 909 Likes: 70 Liked 239 Times in 114 Posts	Re: GM 700-R4 questions..... This is a cable operated transmission, and shifts based on road speed and throttle cable position. As an engine loses power, when it is old and worn out, or out of tune, you have to step on the throttle more to get the vehicle down the road. Sometimes we have seen this happen if the catalytic converter gets plugged. Many times these old vehicles are so weak, the throttle position needs to be opened so high that all the upshifts feel delayed, the fourth gear shift is at a higher mile per hour then you are going. Does the transmission shift into overdrive if you backoff the throttle but downshifts back into 3rd if you step back into throttle , to maintain road speed ? Same could be happening with the TCC. There is a throttle position load release for TCC. So once the TP is higher than a calibrated number, say 30% then TCC will not come on.

08-06-2010, 10:44 PM	#4
Greg Reimer 7376 VIP Member Join Date: Nov 2008 Location: Glendora,Calif. Posts: 1,136 Likes: 172 Liked 705 Times in 219 Posts	Re: GM 700-R4 questions..... I have a 91 Chevy Silverado 1500 pickup,350,TBI,700R4, and it did that. Brake light switch worn out. It kept the TCC and the cruise control from working. Replaced it, truck is fixed. Try that first.

08-07-2010, 11:12 PM	#5
Greg Reimer 7376 VIP Member Join Date: Nov 2008 Location: Glendora,Calif. Posts: 1,136 Likes: 172 Liked 705 Times in 219 Posts	Re: GM 700-R4 questions..... I just had another thought regarding the issue your S-10 Blazer has. It seems that the computer PROM in the GM computer is probably expecting to see a drop in engine RPM after 50 or so MPH,and it doesn't see it. If the torque converter clutch is not applying,it's in a mode of less than 1:1. It's a pretty loose converter, so the discrepancy is being seen between the vehicle speed sensor(which also runs the speedometer), and the engine speed sensor, which is picked up probably by the tach signal in the distributor. The person who suggested that you test the torque converter clutch apply solenoid for proper operation made a good suggestion.The diagnostic trouble code(DTC) would be caused by that excessive engine RPM at that road speed and that seems to all make sense. Identify the DTC, and that should make a proper diagnosis probable. Since you indicated that it was an intermittant condition,then got worse, it's probably something like that. If the trans fluid is all brown,smelly, and full of big particles, then that was probably the result.Good luck with your project!!

08-08-2010, 08:20 PM	#6
ss wannabee Senior Member Join Date: Jun 2005 Posts: 663 Likes: 0 Liked 7 Times in 7 Posts	Re: GM 700-R4 questions....are Thanks for all the responses...Unfortunately, work and family issues took up most of my spare time this weekend and had little time to investigate. I DID manage to get a hold of a GM service manual for the vehicle...and it has diagnostic troubleshooting charts which mentioned most of the stuff you've said. Looks like I can electrically test the solenoid and brake switch through the ALDL connector with a test light...and I'll do so. BTW, the Blazer doesn't have antilock brakes...I think they came a year or two later. The trans fluid seems ok in color and smell on the stick...What I might do is just CHANGE the solenoid anyway along with the filter and fluid. I bought the piece some months ago...but I'll check the resistance Rob..just to see...I saw that the GM manual says the sol. is "junk" if it measures LESS than 20 ohms,,,,maybe the working "spec" is 20-30 ohms? Alan...you mentioned a "stacked shift" situation...YES this vehicle has done that...ALSO intermittently for the last 10 years or so....sometimes loading up the vehicle so badly that I'm forced to downshift. That's one reason why I'm leaning towards solenoid replacement. The Blazer is driven in the overdrive position..it works fine...no need for manual shift.

08-08-2010, 08:45 PM	#7
ss wannabee Senior Member Join Date: Jun 2005 Posts: 663 Likes: 0 Liked 7 Times in 7 Posts	Re: GM 700-R4 questions..... Forgot to mention but the tech at the garage next to work has been too busy to scan the vehicle. So I tried the "old-school" method with a paper clip and counted the flashes. What I got was Code 32...which is an EGR system malfunction. I watched through 3 or 4 cycles to make sure it was the only code....It was....NOT sure if the scan tool could "find" more...but it can give engine temp,TPS voltage, and other stuff that might be relevant. I'll still try to have that done. I don't think this is related to the trans problems but.....I want to point out that this code "sets" ONLY when I attempt to drive the Blazer on the highway...and the engine rpm is over 3,000...heading to 4,000 when the overdive doesn't work. When the o.d. is working properly, I don't think the engine speed goes over 3 grand...and I highway drive at the speed limit...I "baby" the vehicle...Whoever mentioned "easing" up on the throttle to get overdrive...I've tried that recently...NO results lately...although it has worked in the past.... I don't think the converter is clogged...perhaps the opposite....NOW it's time to try some things.....Thanks again, Guys!