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Discussion Starter · #1 · (Edited)
hi, i had posted about the two shift patterns. well i had no responses, so i went to a&b tansmissions who installed the tranny 3 years ago. they put a scanner on it and came up with p0748. line pressure control solenoid. in the last 3 years i have had no issues with the tranny. 2 weeks ago bill heath personally installed his newest computer. shifting was hard, firm and fast. then the next day it was still nicer than stock but not as hard, firm and fast as when bill drove it. on a 50 mile drive i stopped at a light and upon shifting the hard, firm and fast shifting was back. this happened a second time and yet a 3rd with driving some distance, anywhere in between 10-50 miles, it was not as i leave the driveway but some miles into the drive on all occasions. it was also on different days and when i shut the engine off to run into a store i restarted and drove off with it going back 2 the better than stock but not as good it had two minutes before. a&b told me when they install new tranny's they do so with a shift kit. ya right. never felt like it had any shift kit. i put a shift kit in an 81 t-bird and it noticeably changed things so i have an idea what it can do. leaves me wondering what kind of shift kit a&b put in. is it possible this may be tripping a code. the tranny shop doesn't know if the computer is causing the code or it's an internal fault. i like the hard, firm and quick shifting and wondering should i open up the tranny and put a transgo shift kit in or what. also what might it cost to replace the solenoid and is it easy to do. my backyard mechanics level says i can do it. i did the t-bird. just never replaced a solenoid on a tranny..... Ed

1. Fluid level okay while running, warm, level surface. YUP
2. Speedometer reading correctly YUP
3. Shifting normal/hard YES AND NO
4. Shifting into OD okay? YUP
5. Any service engine light: yes/no NO
6. If SES light on, what codes do you have? LIGHT NOT ON SCANNED P0748
7. Model year: 98 GMC DUALLY
8. Describe symptoms: HAS TWO DIFFERENT SHIFT PATTERNS
9. Does the engine come up to full temperature? YUP
10. Any service work recently done that may contribute to your issues. NEW HEATHS COMPUTER, HO INJECTORS
 

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Have you called Bill to see if he may have had this problem with anyone else? To bad it isn't OBD-1, at least then you could pop the old chip in it.
 

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Discussion Starter · #3 ·
i talked with bill today, he says nothing in their computer program would trip the code. i believe that to be true or he would damage his golden reputation. he feels the line pressure solenoid may be getting a command from the computer to do things it has never done before and a minisule piece of crud may have dislodged clogging the valve. he kindly offered to send a new computer with stock shifting firmness. i will tke it to the shop that installed the tranny and ask them for advice. i certainly don't need to pay for a new solenoid if that does not fix the problem. and once they start getting into it as far as fixing goes where does it end. anyone know how difficult fixing this on my own would be. where is the solenoid or valve. i am now considering taking bill up on his offer and doing a transgo, but bill "THE 6.5TD EXPERT" advises to stay with stock shifting and let his computer do the work.
 

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