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post #1 of (permalink) Old 08-07-2000, 10:57 PM
Zooman
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Transmission won\'t shift to 3rd!Help

I finally fixed the brake problem today so I took my truck for a rip down the road but it wouldn't shift to third. I tried doing it on the column but no luck.
Any ideas? The tranny is a th350 on a 78/80 pickup with a 350. Next weekend I am going to change the filter and fluid, I am hoping this will do it.
How do you test the module or what ever it is that comes off the passenger side of the tranny and has a vaccuum line that runs to the carborater.
I would really appreciate the help.

Zooman

[img]/wwwthreads_images/icons/crazy.gif[/img]<font color=blue>78 Chevy 3/4 in the rough</font color=blue>
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post #2 of (permalink) Old 08-08-2000, 01:17 AM
**DONOTDELETE**
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Re: Transmission won\'t shift to 3rd!Help

pull the line off the trans. near the trans if fluid runs out of vacum line modulator is bad, also you should have strong vacum on line hope this helps!

88 1500 4X4 6 in. SUPERLIFT, 35X12.50BFG AT

post #3 of (permalink) Old 08-08-2000, 09:08 AM
Zooman
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Re: Transmission won\'t shift to 3rd!Help

Thanks for the help. I pulled off the vacum line and there was no oil. How do I test for vacum and where do I test.
Thanks

Zooman

[img]/wwwthreads_images/icons/crazy.gif[/img]<font color=blue>78 Chevy 3/4 in the rough</font color=blue>
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post #4 of (permalink) Old 08-10-2000, 10:21 AM
Zooman
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Re: Transmission won\'t shift to 3rd!Help

Does anyone know a good transmision site that deals with th350's?

Zooman

[img]/wwwthreads_images/icons/crazy.gif[/img]<font color=blue>78 Chevy 3/4 in the rough</font color=blue>
post #5 of (permalink) Old 08-14-2000, 02:09 PM
**DONOTDELETE**
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Re: Transmission won\'t shift to 3rd!Help

If when you drop the pan you find a pile of metal up by the bell housing your problem is BIG. Those chunks of metal are the forward sprag. What is happening is you get a 1st and 2.5. Your not really in second but your not in 3rd. when the sprag goes it will let the foward drive drum rotate backwards and it sort of gets you between gears.If indeed this is what happend then more than likly the foward drive drum is damaged and a good chance the pump has some damage also. A TH350 is a pretty easy tranny to work on. I was flat broke and decided to try rebuilding mine last year (same symptoms) and it was easier than I thought. J.C.Whitney, Jegs and summit all sell rebuild kits. Your looking about $100 for the rebuild kit that includes seals, steels, and clutches. The add what the price of what other parts were damaged. I hit my local Tranny shop and they sold me a used foward drum, sprag and a rebuilt pump for $75. Bring the busted parts. GM uses a foward drive drum that was very simular in a lot of trannys and they will work fine. Some ran on less clutch and you can use the old piston and then it will take the same clutches as before.
The 2 big problems that you will find when rebuilding on is if the seal is still soft on the pump that your going to have a heck of a time poping it loose. The tranny shop has a slide hammer deal to pop them out. The second is you need a compressor tool to dissassemble and assemble the pistons. I was able to get creative with a harmonic ballancer puller and a few 3/8 bolts.
If you don't find the pile of parts then you may have a problem in the valve body and it may be just a matter of cleaning it out.

Grim-Reaper
http://www.grimsk5s.coloradok5.com
post #6 of (permalink) Old 08-15-2000, 09:42 AM
Zooman
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Re: Transmission won\'t shift to 3rd!Help

Thanks for the input Grim. You would never guess but the truck was actually in 4low. When I took the truck for another test drive I drove nice and easy and could feel it shift 3 times. So I new that it had to be in 4low. Also when I went to change the tranny filter I realized that I don't have a th350, I have a th400(great news).
Thanks again for the help, nice web site by the way. I am also building a web site at coloradok5 to.

Zooman

[img]/wwwthreads_images/icons/crazy.gif[/img]<font color=blue>78 Chevy 3/4 in the rough</font color=blue>
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