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1995 Suburban transmission problems

04-30-2005, 03:28 PM
I have a 1995 Turbo diesel Suburban, depending on the day it will not shift out of first gear, this problem can be started or fixed by turning the engine off and restarting it. I just had a brand new transmission put in and it is doing it again after having it out 2 times, any ideas whats causing this?

05-01-2005, 11:18 AM
I'm not too familiar with diesel units,but I will offer a couple suggestions.Is the speed sensor functioning properly?Second,is the vaccum pump functioning on the engine?The diesels may use a boost pressure sensor to inform the computer when to do the shifts in the tranny.Similar function as the map sensor in a gas engine to measure manifold pressure.I hope this will be helpful because it appears that the problem is not the tranny.

05-01-2005, 11:26 AM
I don't know about the speed sensor, I have had problems with the gauges also, it started with the speedo jumping back and forth say 5 mph so when I am at 60 it would go to 55 then 65 and then stabilize again, then at one point all my gauges went dead while I was driving and then I hit a bump and they came back on again. This seemed to get worse when the trany problems started, I don't know if this was a coincidence or what it was. Also my fuel gage seems to be jumpy now to.

How do I check vaccum pump and the speed sensor

05-01-2005, 11:44 AM
Reading your recent post,I would check your electrical connections.Battery,starter and grounds.Electrical problems can cause many driveability problems.Make sure they are clean and tight.Above the left rocker cover there is a soleniod that controls vaccum to the turbo.You can disconnect the vaccum lines off the soleniod and with the engine running,you should feel vaccum on the hose that comes from the vaccum pump.I hope this will aid you even more.

06-13-2005, 01:35 PM
I also have a 95 "burban", and have same problem...SOMETIMES it will not shift into overdrive, guages go dead, tach goes wild, speedo goes from 0 to real fast even the shift indicator light goes out......problem can usually be fixed by stopping, turning everything off, letting it sit for a min. or two, turning key on, but "not starting" pump gas to floor several times, start engine and go......sometimes I have to do this a couple of times ...this is a 350 gasser also, not a diesel....any thoughts??



***all connections are good...

06-13-2005, 07:05 PM
There should be two ground straps that are along the right frame rail just before the firewall.Are these straps in place and secure?It sounds to me that it is an electrical issue.I know you stated that the connections are good,but when things like you descibe occur this is where I go first.What about the computer connections?Clean and secure?The only other suggestion that I have is that within the wiring harnesses,some wires get crimped together and it could be possible one of these could be causing you problems.I refer to this because I worked on a 99 pick-up for two days with instrument cluster guages not working all the time ,only to find out that some wire from the cluster was not making a proper connection within a designated splice within the wiring harness.This is what the verdict was from the GM dealer.Since then there has been no problems with the guages.I hope this will be of some assistance and others will be able to help.

06-14-2005, 03:07 PM
Thanx Chuck...willl check out the straps...seems like I've checked everything else....sigh....
Thanx again

06-16-2005, 07:10 PM
I have had this problem once, the fault was a conector pin on the harnes on the car, that is mounted on the transmission (left rear side of transmission 4L80E). The "she" pins in the conector did not have enough tension,

06-17-2005, 07:30 AM
These problems could also be symptoms of your ignition switch going bad and not sending power to the tranny at times

06-23-2005, 07:53 PM
Well, a GMC shop in Graingeville Idaho has it now....wonder how much THIS will cost!! Any gusses.....Thanx to all... :crying:

06-29-2005, 06:20 PM
OK...News.... received a call today, and there was a wire grounding out to the block by the starter,,,,AND the ignition switch was bad also!!!!!

Still have not had the nerve to ask whet this is going to cost me....but will keep all interested, posted..

Scott email me


07-23-2005, 11:08 PM
Ok, here's the deal guys, I need some of your opinions.
I took the truck back to AAmco after having the same problem and they openly admitted that "the problem all along was the ignition switch"
What should I do and what should I expect? The truck was misdiagnosed and I need to be reimbursed for the Transmission.
What do you guys think?
Please refer back to the original post.

02-02-2006, 09:49 PM
Guess what.You are not the only one to find out that your ignition switch is the cause of tranny problems.My 99 suburban just started to act up with the tranny.Tach and speedo didn't work,check guages lamp on,service engine soon lamp on,no shift indicator and poor transmission perfomance.A collegue at work fixed a pick up in which the shift indicator wasn't illuminated and poor tranny preformance.Ignition switch was the problem.So with my problems that is directly where I'm headed.There is a fuse in the dash side panel #20(PRNDL) that gets ignition power to feed solenoids in the tranny and provides power to the check guages lamp.If this doesn't get power from the ignition switch,no power to the shift solenoids.This info maybe little too late,but maybe it will help someone in the future.

02-18-2006, 03:43 PM
Hi Eddy. I have had this problem with my 95 Diesel for years. I am no mechanic, just a Mom but do want to tell you that you have to wait for the glow plug light to go off before starting the engine. My husband has always told me that when the engine is warm that I do not have to wait for the glow plugs, but taking his advice this getting stuck in first gear happened all the time. When it did I would have to come to a complete stop, turn the engine off and then restart giving the glow plug light time to go out and also giving it just a second before putting it in gear. With the stereo on, the kids in the back seat and my mind on the tasks at hand; I have found myself half way down the road - engine screaming. Probably not a nice thing to do to your truck. Could it be just a matter of timing? Waiting that extra moment has worked for me.
PS: Nice to know someone who also has a diesel suburban, I have never seen another on the roads around here. Is yours a 3/4 ton?

06-03-2006, 11:47 PM
We'll I have taken AAmco to small claims court and won. The settlement was a joke but at least Aamco has another bad mark against them, I will NEVER, EVER take any vehicle I own back to them, AAmco is a joke!!!!!!! They call themselves the experts, expert scammers maybe.

This is a good forum and a great place to get answers, I will start here the next time I have troubles with my truck.
Alice, yes my truck is a 3/4 ton, too bad diesel is so expensive now, still better than regular gas I guess. I always wait for the glow plugs to heat up before I start the truck.

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