GMC tranny rebuild

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  #1  
Old 08-24-05, 06:50 PM
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GMC tranny rebuild

97 Jimmy 4X4 4.3L 97,000
I need a tranny rebuild. I've gotten a couple estimates with very different parts needed.
1)includes a corvette servo , 13 vane pump $1600
2)uses old pump and servo the rest seems to be the same $900
Are these common upgrades? Are they neccesary? Is it worth the difference in price? I appreciate any input.
 
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  #2  
Old 08-25-05, 08:56 AM
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Location: Michigan
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upgrades

Hi, A 1997 GMC Jimmy is a Pulse Width Modulation transmission and should have the upgraded pump already. As far as the Corvette servo I don't believe this will be a necessary upgrade for your application either. I would suggest installing an updated sun shell as these commonly break causing a loss of reverse, second and forth gear. There is a shell available in the "aftermarket world" that is designed to correct this problem. I put this in my own truck as well as all of my customers. These also have a common problem with a code 1870 for a transmission component slipping. This is reffering to the torque converter clutch slipping and can be corrected with the "proper" type of "shift kit" that will replace the valve in question. I would highly recommend installing this at the time of repair. In contrast repairs for this transmission in my area will run upwards of $2000.00 for a complete job including removal and installation. And the upgrades I have described. I hope this helps.
 
  #3  
Old 08-25-05, 10:07 AM
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Originally Posted by jaws
Pulse Width Modulation transmission

I am not familiar with that term for labeling a transmission, but a lot of things on cars are pulse width modulation and have been for years.

Is this technique used to measure shaft speeds in order to know when to change gears, or is this technique used to control electrical motors that control the hydraulics.
 
  #4  
Old 08-25-05, 04:06 PM
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Thanks for the input. Actually the cheaper estimate includes the sun shell. I don't know where I'm going to take it.
 
  #5  
Old 08-26-05, 06:38 AM
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P.w.m.

Hi Shottys

The 4L60-E transmission uses 2 electric shift solenoids to control transmission upshifts and downshifts. It also uses a pressure control (force motor) solenoid that controls hydraulic line pressure and a Pulse Width Modulation (PWM) solenoid to control the fluid acting on the converter clutch valve that conrtrols the TCC apply and release. The Pulse Width Modualtion system is used for a gradual apply of the Torque Converter Clutch as opposed to the previous method of a solenoid that just turns it full on and full off with a bit more harsh application. If they slowly apply the torque converter it is less noticeable therefore smoother. Hope this answers your questions.

Good luck with your transmission repairs Dan75321
 
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