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Turbo 350 Trouble in 85 gmc

3K views 7 replies 5 participants last post by  ronb 
#1 ·
ok im starting to get fed up with these turbo 350s although i never had one rebuilt or ever attempted to rebuild one ive gone threw 3 of them already in my 1985 GMC 1/2 ton 2wd 350 mild motor. the last trans i blew did not leak or anything would not go forward or reverse when it blew it started slipping and catching then it just wouldnt go now more and made a slight vibration in gear although i checked the fluid and it was still pink i pulled the pan off and at the rear of the valve body there are 3 valves it looks like and the first one from the left looks like a half of valve showing me it cracked in half

if i wanted to rebuild the transmission myself what special tools would i need and how much would it cost me ?

also
any 1 in the new jersey area have a 350 turbo long tail they might be selling?


thanks in advance guys

joe
 
#3 ·
in my opinion a lot of transmission failure could have been prevented if the cooling would be better, over here in europe where we have more stop and go and higher highway speeds all american cars witk A/T are equiped with an extra trans cooler since the dealers where getting tired of swapping transmissions. since this is your third there might be something wrong with that, or maybe you just had bad luck with a couple of used items. but at least check your cooling.

regards Bas
 
#4 ·
The TH-350 is a tough transmission and can be built just about as strong for racing as the TH-400.

Rebuilding a trans does take some specialized tools but if you're local trans shop is willing to replace the bushings for you for a few bucks you can save yourself the purchase price of the tools. All you'll really need are three 5" C clamps and a pair of snap ring pliers besides your normal tools.

First get a good manual on the TH-350 and then spend the money for the rebuilding video. I can't stress this enough. The video is worth its weight in gold when it comes to rebuilding one of these transmissions. A rebuild kit will cost you about $150 and should include everything you will need with the exception of any hard parts that might have damaged.

While you're at it you might as well install a shift kit and a good trans cooler. Heat is the main enemy of your trans and the cooler it runs the more abuse it can take before breaking.

The TH-350 like all automatic transmissions is a pretty complicated piece of machinery and requires someone who can keep everything organized. When disassembling the trans put all small parts in zip lock freezer bags and label them. It’s the only way to keep everything together. Also be very careful when cleaning and rebuilding the valve body. Many of the valves are multi piece assemblies and if you get the parts mixed up you will never be able to get it back together correctly.

Now that I've scared the hell out of you don't be afraid to tackle rebuilding one. Just keep things organized and take your time and you should be fine. And by all means get the video.

Good luck.

Centerline
<a href="http://www.hotrodsandhemis.com" target="_blank">http://www.hotrodsandhemis.com</A>
 
#5 ·
i second that i've rebuild about 12 of them , did not dare to, but i also bougt a manual and a video while i was on a trip in your country, since then i just tried one, did everything slow and took a lot of space took keep track of all the stuff that was coming out, but it worked.

since we don't have many specialized shops here i had to make some tools for the bushings, but once you done it once it will be easy.

goodluck

Bas
 
#6 ·
received your pm, 700R4 is a direct bolt in for the long shaft 350, but the 700R4 is not a heavy duty trans, in stock form they work well but do not like full throtle take off, 3rd gear clutch weak. 350 not that hard to rebuild, but for the first timer seek help. GOOD LUCK.
 
#7 ·
when i got the truck the trans was shot already and i just finished it in my alley way. the second and 3rd trans i blew from normal use and occasional spinning the tires and as far as torque convertors go i used the one i got with the junkyard transmissions that i bought also a factor i left out i never bled out the cooler lines for either of them so im sure there clogged with clutch material i took it off today along with the lines and sure enough theres clunks of stuff in there which led me to believ fluid prolly didnt even circulate through so i junked it and the lines im gonna get a whole new set up and some braided lines and mount it to the inner frame found a nice 400hp trans on ebay for $525 shipped with a 1 yr exchange warranty so thats prolly my best bet and ill also be adding a trans temp guage!!!!


i really appreciate all your help and im keeping the old 350 and gonna tackle taking it apart piece by piece and learning how to rebuild them i can get cores from my uncle who owns a junkyard round here so ill build em and sellll em i rebuilt a a4ld o/d trans in a ranger but that was simple just thought the chevy might need diff tools
 
#8 ·
Joe; I do not recomend you buy that tranny on e-bay! you do not know what you are getting? If you do? doe`s the seller also waranty the installation and removal and shipping charges(both way`s)?You could get your 350 rebuilt for that kind of money by a pro and probably installed for you? the right way!
 
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