Author Topic: 86 c10 4.3 Radiator Swap w/ V8  (Read 5512 times)

Offline 75gmck25

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Re: 86 c10 4.3 Radiator Swap w/ V8
« Reply #15 on: November 26, 2019, 06:53:36 AM »
The TH400 is a very good transmission, but overkill for your application.  Its stronger than a TH350, but has more parasitic loss (loss of HP due to internal friction).   Its more appropriate for heavy duty use, such as racing, towing, mudding, etc.

The TH350 was used with all variations of 350 engines, including 3/4 ton 4WD's like my '75 K25, so it is definitely strong enough for anything but very extreme conditions.  TH350's are usually cheap to buy, and relatively easy to rebuild and/or upgrade.   

Another option would be the TH700R4 overdrive.  They were introduced in the '82 trucks, but you want to get a later version after they upgraded them for more reliability.  Also make sure you get the TV cable adjusted right on a TH700R4, or you will shortly have major problems.  Low rear end gears (3.73?) and a 700R4 would help make that V6 feel powerful.

Bruce

Offline buter1ma

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Re: 86 c10 4.3 Radiator Swap w/ V8
« Reply #16 on: November 26, 2019, 07:17:54 AM »
I did not know that about the TH400. I have thought about the 700R4 but I have the 10 bolt rear end gearing (2.72), so Ill never use the over drive. Plus I heard the 700R4 aren't as robust as the 350/400.

Offline zieg85

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Re: 86 c10 4.3 Radiator Swap w/ V8
« Reply #17 on: November 26, 2019, 09:37:22 AM »
FWIW the TH350 short tail shaft is your best bet.  In 86 GM had already phased out the TH350C and the standard 3 speed automatic became the TH400.
1985 C30 Custom Deluxe Ext. cab 5.7L TH400 3.21 
1985 C20 Scottsdale 7.4L 4 speed 3.21
1986 C10 under construction
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Offline Stewart G Griffin

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Re: 86 c10 4.3 Radiator Swap w/ V8
« Reply #18 on: November 28, 2019, 08:55:02 AM »
I will have a donor steering column from a suburban with tilt, cruise, and delayed wipers. By the time I am done with it, it will look like a custom deluxe but have the comforts of a Silverado.

Why do you say "yes they did come behind 4.3's   Not sure why, but they did"?

Probably because of this:
FWIW the TH350 short tail shaft is your best bet.  In 86 GM had already phased out the TH350C and the standard 3 speed automatic became the TH400.

i always thought it was odd that the TH-400 came behind the 4.3----totally overkill---sort of  like using a sledgehammer to crack peanut shells.

Then i thought about it, and i think GM stopped producing the TH-350/350C by 81?   Gm still wanted to offer a 3-speed auto with the trucks and the only one left in production was the TH-400?

2) Now about your radiator question:
Yes, again, the upper and lower coolant hoses from the v-6 should plug directly into the v-8 radiator outlets.  No need to buy different hoses.    The heater hoses should also plug right in.

For an auto trans to work with a v-8 radiator, then you either need to get the hard-metal trans cooler lines (or make your own) for the v-8 radiator -OR- and i think this is easier, get rubber or steel braided lines:
https://www.jegs.com/c/Fittings-Hose/181705/10002/-1?N=1181705&Ntt=trans+cooler+lines&Tab=SKU

a) If you go stock metal lines, i'm not sure if TH-400 and TH-350 use the same exact lines, so you may have to go trans specific.

b) Irregardless of a), i'm pretty sure you need to go chassis specific.  For example lines from a monte carlo likely will NOT fit a truck

So, you can see why i think going flexible rubber  or steel braided line  is much easier, cheaper and faster.   If you decide to go this route, we can help you.   There may even be a kit that i haven't found.

Offline buter1ma

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Re: 86 c10 4.3 Radiator Swap w/ V8
« Reply #19 on: November 30, 2019, 07:48:29 AM »
The thought was buying a radiator from rock auto for a 5.7 that comes with trans cooler ports. Then I won’t need the external trans cooler. Then it should just be standard lines from transmission to radiator.

Offline Stewart G Griffin

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Re: 86 c10 4.3 Radiator Swap w/ V8
« Reply #20 on: November 30, 2019, 08:56:41 AM »
The thought was buying a radiator from rock auto for a 5.7 that comes with trans cooler ports. Then I won’t need the external trans cooler. Then it should just be standard lines from transmission to radiator.



Next, how are you going to operate the shift selector on the auto trans?
« Last Edit: November 30, 2019, 09:12:28 AM by zieg85 »

Offline buter1ma

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Re: 86 c10 4.3 Radiator Swap w/ V8
« Reply #21 on: December 05, 2019, 06:36:52 PM »
I am getting a steering column out of a suburban.

Offline zieg85

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Re: 86 c10 4.3 Radiator Swap w/ V8
« Reply #22 on: December 05, 2019, 07:37:54 PM »
If your column is still in good condition it is worth quite a bit.  Those purist, old school like the 3 on the tree.  I gave up my search after about 6 years of looking to find a good column 84-87 with linkage.  I just couldn't find one at any cost.  Replacement parts were NLA as my truck was converted to the 3 speed floor shifter after the shift collar broke on my 86.  I wanted to go back stock but opted for a 4 speed instead and replaced the column accordingly.
1985 C30 Custom Deluxe Ext. cab 5.7L TH400 3.21 
1985 C20 Scottsdale 7.4L 4 speed 3.21
1986 C10 under construction
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Offline buter1ma

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Re: 86 c10 4.3 Radiator Swap w/ V8
« Reply #23 on: December 21, 2019, 07:11:41 AM »
I have decided to just go with the TH350 short tail as my transmission instead of the TH400. Also, Ill be picking up a 350 SBC that has been rebuilt but has been sitting for a long time. Going to tear it down and see what needs to be done or not done.

Offline buter1ma

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Re: 86 c10 4.3 Radiator Swap w/ V8
« Reply #24 on: December 22, 2019, 07:29:52 AM »
Ok, I am a noob. The more I learn the more I change my mind. Now I am thinking 700R4....

I am like a kid in a candy store lol.

Offline 75gmck25

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Re: 86 c10 4.3 Radiator Swap w/ V8
« Reply #25 on: December 23, 2019, 06:25:44 AM »
Let me complicate your decision even a little more - take a look at the 200R4 overdrive also.   It has better low gear spacing than the 700R4 (which has big jump from 1st to 2nd).  Its the same length as a TH350, so its sometimes used to replace a TH350 without needing to change driveshaft length.

Bruce

Offline zieg85

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Re: 86 c10 4.3 Radiator Swap w/ V8
« Reply #26 on: December 23, 2019, 09:43:27 AM »
this may help
1985 C30 Custom Deluxe Ext. cab 5.7L TH400 3.21 
1985 C20 Scottsdale 7.4L 4 speed 3.21
1986 C10 under construction
https://www.facebook.com/groups/248658382003506/

Offline JohnnyPopper

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Re: 86 c10 4.3 Radiator Swap w/ V8
« Reply #27 on: December 23, 2019, 08:20:57 PM »
If you're in it this deep go for an overdrive, you won't regret it, but you might be sorry if you stay with a 3-speed.  ;)
1957 Apache 3100 235 Inline 6, 3 on the tree
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Offline VileZambonie

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Re: 86 c10 4.3 Radiator Swap w/ V8
« Reply #28 on: December 24, 2019, 07:30:09 AM »
Zieg, post that image in the tech section for reference.

Unless you just putt putt around town, a 3 speed just won't cut it these days.
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Offline buter1ma

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Re: 86 c10 4.3 Radiator Swap w/ V8
« Reply #29 on: December 24, 2019, 08:08:55 AM »
That is why I am going to go to the 700r4. It might be more then I need but if I decide to use it more on expressway or change my rear gearing. The overdrive will be already there already.

I ended up getting that 350 engine on Saturday. Going to start tear down after Christmas.