Difficulty in rebuilding a TH350 - Chevelle Tech
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post #1 of 13 (permalink) Old Nov 5th, 00, 6:18 PM Thread Starter
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Join Date: Nov 1999
Location: sacramento ca
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On a scale of 1 to 10 how hard would it be to rebuild a TH350.And what special tools if any are needed.I have the ability of a 8.5 or so.The only thing I have never tackled is a rear end(Ihave never had to) and the mysterious automatic transmision.So any insight would be helpful.I presently have a Th400 So i was wondering if I should go to the recycle yardand get a 350 or stay with my 400 so Please help
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post #2 of 13 (permalink) Old Nov 5th, 00, 7:07 PM
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I didn't find rebuilding a 350 to be all that hard my first time, just take great care in checking out how things come apart and take pictures. I had to do it 5 or 6 times until I had no pieces left since I didn't pay close enough attention when it came apart. I got an Illustrated Parts Breakdown from a book at the library, but I should have bought the Chevy Tranny book.

Depending on what engine you have, I would stay with the 400. Stronger engine, and a swap to a 350 will require modifications.

Good luck to you, and if you need any help on the way, this place is the right place to ask.

(oh yeah, and by the way, the rating would be a 6 on my scale, way below dismounting a tire with no tools, and way above putting gas in it! )

70 Impala Sport Coupe (283)"Green Goddamn!"
63 Oldsmobile Dynamic 88 (394)"Hoopty"
61 Chevy Stepside Pickup (350)"The Pickle"
49 Plymouth Special Deluxe (427)"The Mayflower"
77 Chevy Blazer (350)"The Moo Machine"
66 Chevelle (I wish, still looking)

[This message has been edited by ledsled (edited 11-05-2000).]
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post #3 of 13 (permalink) Old Nov 5th, 00, 9:44 PM Thread Starter
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The only thing about the 400 that I dont like is the fact that it takes 50 more horsepower to turn than a 350.And the whole thing about an electronic kickdown has me bothered.I have been running this combo(383 and aTH400) in different projects for 3 years and have yet to hook up the kickdown.Will it make a seat of the pants difference?

Also this goes to show you how much I know about transmissions,Iput type f in my 400.Doooh!!! I didnt know the difference until my buddy came over and saw the bottles on my workbench.How much will this hurt my tranny?One more thing ,if I got a video on how to rebuild my 400 do you think I could do it. Thanks fella
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post #4 of 13 (permalink) Old Nov 6th, 00, 12:32 PM
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Get Ron Sessions' bokk on rebuilding the TH350. He takes you through the entire process. Well worth the $20 or so.

Pat Kelley
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post #5 of 13 (permalink) Old Nov 6th, 00, 2:37 PM
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50 hp more? More like 10-12. Someone on this site gained .08 in 1/4 going to a th350 from th400. Will not "feel" a difference between the two.

70 Chevelle 15.01 @96
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post #6 of 13 (permalink) Old Nov 6th, 00, 3:53 PM
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I put together an OD transmission that I did not take apart. It took some time, but I figured out how the whole assembly went together without any pictures just so I knew I had everything.

The transmission is not much harder than a motor, in my opinion. There are just more parts.

You have to keep things clean and not skip any steps. For example, if the book says you need a pump alignment tool, get it or get someone to do that step.

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post #7 of 13 (permalink) Old Nov 6th, 00, 5:15 PM Thread Starter
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Ok guys I think I am going to go for it.Any performance mods that you would recommend?
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post #8 of 13 (permalink) Old Nov 6th, 00, 7:33 PM
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Ron Sessions' Turbo 350 book has some great performance tips, including running extra clutches, and telling you where you may want heavy-duty parts. Highly recommend that book!
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post #9 of 13 (permalink) Old Nov 6th, 00, 7:55 PM
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I am running type F in my TH350 also, B&M recommends their fluid B&M trick shift or type F....I dont know if its the flow characteristics for shifting,or if it takes the heat better or what, but if B&M recommends it, I will use it

Bob West
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post #10 of 13 (permalink) Old Nov 7th, 00, 12:31 AM
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Rebuilding a TH 350 is not hard, I would say the degree of difficulty is on the same level as rebuilding a later model carburetor, just a few more parts.

The Ron Sessions book is a big help if you've never done it before. Another good trans book to have believe it or not, is a Haynes manual # 10360 titled 'General Motors Automatic transmission overhaul' This is one of those $20 books that you can pick up in an auto parts store. The photos in this book (there are over 1000) and a lot of the info in it is from B&M. It covers the turbo 350, 400, 2004R and 700R4.

One more thing to consider is that a turbo 350 or 400 will need some of its bushings changed. To do the job right its best to replace the whole set, for that you'll need a bushing driver kit for automatics. Unfortunately these are not cheap, I paid over 400 bucks for mine and it's a smaller kit. If you're going to do this more than once, then it's a good investment, the one I got covers the four transmissions above plus some ford and chrysler trannys.

Finally, is some thing wrong with your turbo 400? if so wouldn't you want to rebuild it? it's a tougher trans, it doesn't take 50 more horsepower to turn than a 350 and Sessions also has a turbo 400 book (nice cover photo BTW) Hooking up the detent switch is no big deal and putting type F ATF in it won't hurt any thing, only big difference between Type F and dexron is coefficient of friction, in other words the dexron is a little more slippery. With type F only difference you may notice is slightly firmer shifts.

Keep the 400, just my opinion.
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post #11 of 13 (permalink) Old Nov 7th, 00, 9:11 AM
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In the back of most HOT ROD, SuperChevy, Chevy Hi Performance magazines, there is an ad for a video tape on how to rebuild a tranny from start to finish for ~ 29.95. I think that would be very helpful. I've been thinking of doing the same on a 700R4 I've got but the thought of installing it and it not working and taking it back out bothers me !

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post #12 of 13 (permalink) Old Nov 7th, 00, 6:38 PM Thread Starter
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Hpx2x426 thanks for all the info! I think I am going to keep the 400 and just rebuild it.The reason I think that I need to rebuild it is because I was racing a buddy when I was spinning the tires pretty bad in 1st gear then it shifted into second.I thought it was spinning the tires again.WellIwent back to see how long it spun the tires before it actually hooked up,no second gear tire marks!So this leads me to beleive that the tranny was slipping in second gear.

Iwas looking at the rebuild kits on ebay and they are 51.00.But if I am going to have this thing apart I want to put heavy duty clutch plates and band in it.Looking at B&M's website last nite It wouldnt be that much to upgrade.30 for the clutch plates and 30 for the competition band.So if I do that what parts can I use from the kit that I buy on ebay?Or would it be cheaper to just buy everything separately? Thanks for all the great replys! I LOVE this place!!!!!!
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post #13 of 13 (permalink) Old Nov 9th, 00, 7:11 AM
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Go with the book unless you have a TV VCR in your garage); And typeF is the way to go for a performance trans firmer shifts is what it's all about.And run a cooler...FRED

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