1983 Chevy Silverado shift issues (search completed) - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Cochise · 08-13-2014, 03:58 PM

Good Afternoon, long time poster, first time reader. My transmission shifted terrible from 2nd to 3rd on my 1 hour trip home when I bought my truck, also my tranny leaked like a siv. I went ahead and replaced the front and rear seals and pan gasket thinking I'd be able to solve the problem of me overheating the tranny because of leakage. I thought if I fixed the leaks, the tranny would not run hot and I wouldn't lose 3rd gear. I did all of that and it feels like it slipped, so I thought, replace the modulator valve. I did that and it still did the same thing as before. I read about turning the set screw in the modulator valve a certain increment in certain directions, STILL with no change. IT WILL kick down for me, but with regular driving the rpm climbs and the tranny slips pretty bad. It shifts fine from 1-2, so I think it's something else. Does anybody have any ideas? Also, I still have a tranny leak from the speedo cable. I put silicone around where the "O" ring is thinking the leak would stop, but it hasn't What is that part called so I can get it from the parts house?

775stepside · 08-13-2014, 05:42 PM

Sounds like your 3-4 clutches are bad. I have rebuilt a couple of these transmissions. Usually the 1-2 are easy as they are at the top of the trans and 3-4 and reverse are at the bottom. I'm pretty positive your clutches are bad.

Can you shift it manually? If you can then you have an electrical problem, if you can't then it's in the guts. It's also good to check the valve body as the holes will wear out where the check balls seat.

donut · 08-13-2014, 06:22 PM

Does sound like fried clutches, though I don't see mention by the OP of 4th gear.
Do you know what's in it for a transmission?
How does the fluid look and smell? little dark, smell burnt?
You replaced the pan gasket, how much "gunk" was in the bottom of the pan?

If it were me, I'd be budgeting for a re-build. Either by me or a local shop. If a shop does it, they should re-seal the speedo gear also.

Cochise · 08-13-2014, 07:08 PM

Thanks for the responses. I'm sorry I didn't mention which tranny I have is the 350. I had my mechanics do seals, pan gasket and filter because I thought it was because of heat like I said. I know it's in 3rd gear because if I hammer it the tranny will kick down. I was hoping it was something easy, apparently not

08-13-2014, 03:58 PM	#1
Cochise Junior Member Join Date: Apr 2006 Location: Rogers, AR Posts: 298	1983 Chevy Silverado shift issues (search completed) Good Afternoon, long time poster, first time reader. My transmission shifted terrible from 2nd to 3rd on my 1 hour trip home when I bought my truck, also my tranny leaked like a siv. I went ahead and replaced the front and rear seals and pan gasket thinking I'd be able to solve the problem of me overheating the tranny because of leakage. I thought if I fixed the leaks, the tranny would not run hot and I wouldn't lose 3rd gear. I did all of that and it feels like it slipped, so I thought, replace the modulator valve. I did that and it still did the same thing as before. I read about turning the set screw in the modulator valve a certain increment in certain directions, STILL with no change. IT WILL kick down for me, but with regular driving the rpm climbs and the tranny slips pretty bad. It shifts fine from 1-2, so I think it's something else. Does anybody have any ideas? Also, I still have a tranny leak from the speedo cable. I put silicone around where the "O" ring is thinking the leak would stop, but it hasn't What is that part called so I can get it from the parts house?

08-13-2014, 05:42 PM	#2
775stepside Registered User Join Date: Mar 2014 Location: Elko, nevada Posts: 286	Re: 1983 Chevy Silverado shift issues (search completed) Sounds like your 3-4 clutches are bad. I have rebuilt a couple of these transmissions. Usually the 1-2 are easy as they are at the top of the trans and 3-4 and reverse are at the bottom. I'm pretty positive your clutches are bad. Can you shift it manually? If you can then you have an electrical problem, if you can't then it's in the guts. It's also good to check the valve body as the holes will wear out where the check balls seat.

08-13-2014, 06:22 PM	#3
donut Registered User Join Date: Aug 2009 Location: S.C. Posts: 1,593	Re: 1983 Chevy Silverado shift issues (search completed) Does sound like fried clutches, though I don't see mention by the OP of 4th gear. Do you know what's in it for a transmission? How does the fluid look and smell? little dark, smell burnt? You replaced the pan gasket, how much "gunk" was in the bottom of the pan? If it were me, I'd be budgeting for a re-build. Either by me or a local shop. If a shop does it, they should re-seal the speedo gear also. __________________ '86 C-30 dually, 454/tbh400 '73 K-20 350/350/205 (sold ) I'm kinda like duct tape- no real purpose, but handy to have around.

08-13-2014, 07:08 PM	#4
Cochise Junior Member Join Date: Apr 2006 Location: Rogers, AR Posts: 298	Re: 1983 Chevy Silverado shift issues (search completed) Thanks for the responses. I'm sorry I didn't mention which tranny I have is the 350. I had my mechanics do seals, pan gasket and filter because I thought it was because of heat like I said. I know it's in 3rd gear because if I hammer it the tranny will kick down. I was hoping it was something easy, apparently not

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