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My Suburban wont shift!!!


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Dubbstar's Avatar
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September 15th, 2009, 2:29 PM   #1  
My Suburban wont shift!!!

I have a 1990 GMC Suburban with a THM700-R4 tranny in it. It shifts from first to second just fine but wont shift into third or fourth. Reverse is ok too. Fluid and filter were changed about 1500 miles ago. no leaks. Any suggestions on what could be the problem?

 
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September 15th, 2009, 3:06 PM   #2  
Posted By: Dubbstar I have a 1990 GMC Suburban with a THM700-R4 tranny in it. It shifts from first to second just fine but wont shift into third or fourth. Reverse is ok too. Fluid and filter were changed about 1500 miles ago. no leaks. Any suggestions on what could be the problem?

welcome dub,..ahhhh the wonderful 700r tranny.....couple questions

1.did it shift into 3rd 4th smoothly before the fluid change/fliter

2.so have you tried to really get on her to make it change?

3.do you hear any strange whinning when in drive?


red

 
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September 15th, 2009, 4:08 PM   #3  
yea it shifted fine before the fluid change. I was able to get it to shift into 3rd by agressively manually shifting it on a test run after I posted. I was unable to check for 4th though. I havent heard any whining.

 
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September 15th, 2009, 4:23 PM   #4  
dub do you know if the shop flushed it or just changed fluid/filter?

 
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September 15th, 2009, 4:25 PM   #5  
I'm just getting the most obvious thing out of the way first. Sometimes it takes a while to completely refill the tranny properly after a filter change.

Have you checked the fluid level lately?

 
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September 15th, 2009, 6:08 PM   #6  
Knowing what kind of trans it is and the age I can guess the mileage is high, the trans is probably done. Check the kick down cable make sure it is attached to the throttle body. If it does not have a kick down cable then there is a switch on the gas pedal assembly. I have only seen the switch 1 time (must be kind of rare) (if I remeber right it was not a 700) on a older Chevy flat bed pick up. I think it cause similar symptoms. If above checks out fine (including the fluid level as stated above) then you need a trans.

 
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September 15th, 2009, 6:11 PM   #7  
I changed the fluid and filter myself. I know about 4-5 quarts gets left in the torque converter, but I put an extra magnet in the pan and dumped 6 new quarts of blood in it. The transmission was shifting beautifully for about 1500 miles, until last night. I pulled over at a citgo and the first thing I checked was the trans. fluid and it was ok.

 
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September 15th, 2009, 6:22 PM   #8  
MD,will debris in the clutches cause this problem?

 
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September 15th, 2009, 6:38 PM   #9  
Posted By: myotherchevyisablazer MD,will debris in the clutches cause this problem?
I do not do any internal trans work so I can not say. However if you are getting to will a flush help, then the answer is no. A flush usually will not fix a problem because by the time it occurs the damage is done.

 
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September 15th, 2009, 7:16 PM   #10  
Alright so here is the latest update on my transmission problem..... I just happen to have one tempermental bowtie! haha! Taking myotherchevyisablazer's advise I decided to really show her whos boss. I put it in overdrive and then put the pedal to the floor. 1-2-3-4 just like that. So, im guessing that maybe it was something with the kickdown cable. Is there a way to adjust that? I know it cant be she just didnt want to come home last night. Could this be a sign of a future problem?

 
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