Author Topic: TH400 not shifting correctly  (Read 2617 times)

Offline RAD77C10

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TH400 not shifting correctly
« on: January 07, 2017, 01:02:13 AM »
1977 C10 350CI - TH400, Last week I drove it to the store, I took off normal from the stop sign & the engine rev. & barely more. Did the same 2nd & 3rd, If I shift it 1st, 2nd, then 3rd manually it slips but not as bad. The truck has 29000 miles on it now, but it sat for a long time. I've had the truck about a year & put about 1500 miles on it. Would a clogged filter do this or do you think it's something else?

Offline VileZambonie

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Re: TH400 not shifting correctly
« Reply #1 on: January 07, 2017, 12:53:04 PM »
Did you check the fluid level?
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Offline RAD77C10

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Re: TH400 not shifting correctly
« Reply #2 on: January 07, 2017, 03:07:05 PM »
Yes I did, in Park on level ground. It's good.

Offline VileZambonie

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Re: TH400 not shifting correctly
« Reply #3 on: January 07, 2017, 03:12:00 PM »
With the engine running right? If so yes you should drop the pan and check to see if the filter and pickup tube (and o-ring) are in tact.
,                           ___ 
                         /  _ _ _\_
              ⌠ŻŻŻŻŻ'   [☼===☼]
              `()_);-;()_)--o--)_)

74 GMC, 75 K5, 84 GMC, 85 K20, 86 k20, 79 K10

Offline RAD77C10

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Re: TH400 not shifting correctly
« Reply #4 on: January 07, 2017, 03:37:30 PM »
Yes running. The pickup tube & o-ring, does the o-ring keep the tube in place? When the o-ring rots, the tube drops?

Offline RAD77C10

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Re: TH400 not shifting correctly
« Reply #5 on: January 09, 2017, 12:39:00 AM »
What is the best TH400 filter to get? Any brand of pickup tube o-ring? Delco, Wix, Fram? What is a good trans. pan gasket?

Offline gunrac

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Re: TH400 not shifting correctly
« Reply #6 on: January 09, 2017, 08:47:37 AM »
1977 C10 350CI - TH400, Last week I drove it to the store, I took off normal from the stop sign & the engine rev. & barely more. Did the same 2nd & 3rd, If I shift it 1st, 2nd, then 3rd manually it slips but not as bad. The truck has 29000 miles on it now, but it sat for a long time. I've had the truck about a year & put about 1500 miles on it. Would a clogged filter do this or do you think it's something else?

29000?..... Are you certain this is the original milage? If so, I'd have to lean toward the seals. A lot of rubber in their. But for 20 bucks, try a filter kit. Pay close attention to what is in the bottom of the pan.
When you first start up after sitting overnite, is there a brief sign of oil smoke, that goes away shortly afterwards?
 
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Offline RAD77C10

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Re: TH400 not shifting correctly
« Reply #7 on: January 10, 2017, 12:20:26 AM »
Yes there is, those valve guide seals? A friends Grandfather bought it new in Dec. of 1977, when he sold his farm. The 1966 Chevy C10 he traded in, had 34000. The Grandfather died 3yrs. later. My friend Dad then got it, & drove it once a month two the store. 20 yrs. later, his Dad gave it to him, & he didn't need it. So it sat on the side of the house, used it to pickup a Christmas trees & a run to the dump a couple times a year, then his son drove it to high school for two years. I paid $3000.00 for the truck & a promise never to sell to anyone else, & when I'm done with the truck he'll buy it back at market value. It has surface rust on the top of the truck, the only rust thru is the hood. it has sat 3 miles for the ocean. It still has the original exhaust grate in the end of the tail pipe. If its not raining this weekend, I'll change the filter & o-rings. Thanks

Offline gunrac

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Re: TH400 not shifting correctly
« Reply #8 on: January 10, 2017, 04:41:45 AM »
Yes there is, those valve guide seals?
Most likely, sounds like it done to much setting around an dryed out your rubber.
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