73-87chevytrucks.com
73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: buter1ma on July 24, 2019, 07:46:24 pm
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Just got a 86 c10, 4.3 with 3 on the tree. 425k miles and everything is original. I want to keep it factory/Oem as possible. I am having a hard time find the right info on how/what to swap out the manual trans for auto. I dont want to change out my rear end so I am thinking a TH350 but I am not sure they put that trans on the 86.
Also want to upgrade things such as adding factory power locks, windows etc.
Any help is appreciated.
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In 1986, the transmission used was a TH400 for the non-OD transmission. If you shop for a short tail shaft TH350 you won't have to change the drive shaft at all. You can either search the yards, eBay or buy aftermarket kit for the PW/PDL options. Being a 1986 it will have a hydraulic clutch which is a very desirable thing to sell if you want to go through switching that out and plugging a few holes in the firewall...(very easy to do) I just made a 1987 an automatic. A column from a 1984 or newer for the column shift parts which your 1st/rev shifter linkage is the same I believe. Welcome from the St. Louis, MO area!!! Have a 1986 C10 as well.
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Welcome
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Welcome! If you are interested in overdrive, you can bolt a 700R4 right up to your 4.3L V6. You will need a flexplate, torque converter, and a good transmission (thanks, Captain Obvious). You will also need an automatic steering column, so might as well look for a tilt column. Make sure that you get all the shift linkage from the column to the shift bracket on the side of the trans. Since the 700R4 uses a throttle valve (TV) cable, you will need the bracket on the carburetor linkage for the TV cable. I'm assuming your truck has a carb, since fuel injection appeared in 1987 (someone correct me if this info is not correct for the V6 trucks). Out back, the transmission crossmember from the 3-speed may not work, so you may need one that is correct for the replacement trans. Finally, you will need to ensure that the length of and yoke on the driveshaft are compatible. Likely, you will simply want the driveshaft from the same vehicle as the donor trans, if the bed length is the same as your truck.
If you go the TH350 route, the part about the TV cable does not apply, but the TH350 has a vacuum modulator that requires a manifold vacuum source from the engine. In all cases I have seen, a hard vacuum tube connects from a short vacuum hose on the manifold to a short vacuum hose on the modulator mounted on the trans.
Regarding the addition of power windows, I would recommend purchasing new PW regulators, as those found in the junkyard usually belong there, or don't have much usable life left (my opinion). New regulators are not terribly expensive, and can be sourced just about anywhere auto parts are sold. However, you will want to avail yourself of the junkyard for the door wiring. Switches can be used from the junkyard, or purchased new. Used switches work until they don't, but they are cheap. You will need to cut holes to mount the switches, since they are not the same shape as the holes for the manual window cranks.
Power door locks should be similar in nature. Score the wiring harness together with the one for PW, but buy the actuators new. I have only recently seen the actuators being sold new. You can find them online if you search. (Vile, I checked the site here but didn't see them. Didn't mean to slight you if I missed them.)
Good luck !
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Thanks for the information.
I found a shop that has a TH400 and a column, installed for $1600 with 3 year warranty on the trans. If I do the TH400, do you know if Ill need to change out my drive shaft too? They didn't mention that when I asked about the conversion/pricing.
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Here is a diagram of transmission lengths. The very shortest TH350 will go in your truck with no driveshaft modification. The shortest TH400 looks like it would work, the front yoke is different
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Make sure that installed price includes the electronic kick down switch on the gas pedal with the wiring.
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Whichever trans I do, won’t I need to add a trans cooler or will the radiator have the ports?
Anyone seen a write up or video on how to do this?
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Whichever trans I do, won’t I need to add a trans cooler or will the radiator have the ports?
Anyone seen a write up or video on how to do this?
More than likely your radiator has been replaced and most replacements are for automatics. But if not I would assume that the price quoted would have everything included and an external cooler was part of the deal.
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Here's a slightly "outside," yet related aspect to this topic:
1) Be careful which torque converter you use---you probably can't use one from a v-8:
This is something i'm going through right now----i did not take this into consideration when i did my swap. i think the v-8 converters are too "tight" for the v-6-----as v-6's and 4's generally don't make as much low rpm torque as 8's. i'm having trouble idling normally---i have to set the neutral idle at about 1300-1400 rpm so i can idle at 700 in gear! Combo generally otherwise runs ok, but the idling and low rpm operation is not normal.
Based on my recent research, there does appear to be two(or more) different converters for different engines, as there are different part numbers indicating different stall speeds.
i will report back as i learn more.
Just something to keep in mind if you keep your 4.3.
2) To buters:
i want to back up and ask why do you want to switch automatic?
No right or wrong answers, just curious? Also, you are considering going from 3spd to 3sp auto?
a) what is your diff gear?
3) To Carl:
Which converter did you use for the auto swap?
Would you happen to have any extra TH-400 converters laying around for a 4.3? ;D
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iirc the v-8 converters are norm around 1400 rpms while the v6 are around 1800
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iirc the v-8 converters are norm around 1400 rpms while the v6 are around 1800
Yes, and you pointed this out before i was done with my swap and i kinda blew it off ;)
Like the saying goes----Live and learn...
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P.S.
These videos popped up on my 'Tube feed somewhat mysteriously/conveniently. Can YTube monitor what you are surfing on other sites?
They go in reverse of what you want to do, but still have some useful info:
https://www.youtube.com/watch?v=5LERy3yrTdA
https://www.youtube.com/watch?v=fw-EOS7SZjE
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3) To Carl:
Which converter did you use for the auto swap?
Would you happen to have any extra TH-400 converters laying around for a 4.3? ;D
Actually my recent work done to a 1987 was to take the stick shift (column, NP440, complete hydraulic pedals and reverse light wiring out) and replace it with all automatic stuff so I could re-sell the truck. Sold it as a roller, ready for the next owner to do what they wish with it. I bought the truck for the transmission and related stuff.
In the past I converted a 1979 GMC from a 3 speed stick to a TH350 and had no issuses with the torque converter regarding idle. It was an inline 6, maybe that was the difference Stewart.
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3) To Carl:
Which converter did you use for the auto swap?
Would you happen to have any extra TH-400 converters laying around for a 4.3? ;D
Actually my recent work done to a 1987 was to take the stick shift (column, NP440, complete hydraulic pedals and reverse light wiring out) and replace it with all automatic stuff so I could re-sell the truck. Sold it as a roller, ready for the next owner to do what they wish with it. I bought the truck for the transmission and related stuff.
In the past I converted a 1979 GMC from a 3 speed stick to a TH350 and had no issuses with the torque converter regarding idle. It was an inline 6, maybe that was the difference Stewart.
Yes, i think inline 6's make a decent amount of torque at low rpm.
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Here's a slightly "outside," yet related aspect to this topic:
1) Be careful which torque converter you use---you probably can't use one from a v-8:
This is something i'm going through right now----i did not take this into consideration when i did my swap. i think the v-8 converters are too "tight" for the v-6-----as v-6's and 4's generally don't make as much low rpm torque as 8's. i'm having trouble idling normally---i have to set the neutral idle at about 1300-1400 rpm so i can idle at 700 in gear! Combo generally otherwise runs ok, but the idling and low rpm operation is not normal.
Shifter hits my leg and also it has over 400k miles so if I am doing a trans I might as well make it the way I want. I have the 2.73 rear end. This truck is bare bones, power nothing, no air, not even a dome light or headliner.
Based on my recent research, there does appear to be two(or more) different converters for different engines, as there are different part numbers indicating different stall speeds.
i will report back as i learn more.
Just something to keep in mind if you keep your 4.3.
2) To buters:
i want to back up and ask why do you want to switch automatic?
No right or wrong answers, just curious? Also, you are considering going from 3spd to 3sp auto?
a) what is your diff gear?
3) To Carl:
Which converter did you use for the auto swap?
Would you happen to have any extra TH-400 converters laying around for a 4.3? ;D
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Shifter hits my leg and also it has over 400k miles so if I am doing a trans I might as well make it the way I want. I have the 2.73 rear end. This truck is bare bones, power nothing, no air, not even a dome light or headliner.
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Shifter hits my leg and also it has over 400k miles so if I am doing a trans I might as well make it the way I want. I have the 2.73 rear end. This truck is bare bones, power nothing, no air, not even a dome light or headliner.
Mine is the same however it has a little over 71,000 miles. Mine was PS delete, no radio, nothing extra
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That is exactly like mine. Are you going to be adding on AC, 350 sbc, auto trans, etc?
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That is exactly like mine. Are you going to be adding on AC, 350 sbc, auto trans, etc?
350 SBC, yes. Going with a NP440 4 speed OD stick (rare MY6 transmission) and if I like the way the truck turns out vintage AC. I have high back Suburban buckets with center console.
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Which trans is the better way to go?
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Which trans is the better way to go?
My trucks if at all possible are manual transmissions. I understand manual transmissions and feel I can drive them efficiently and yield better MPG's. If it breaks I have another on a shelf with minimal down time. I also like the fun factor. My choice of this particular transmission is because it is an OD, was a factory option, and the previous owner already cut a hole in the floor because the original column (3 on the tree) was broken and parts were not available to fix it. I really like the uniqueness of 3 on the tree and I eventually found all the parts to put it back on the column but because the hole was already there and I had the transmission, the decision was easy. My hope is to get 20mpg with this set up. I have the tow and go cam so low end torque is better than a stock cam. The only question I have yet to answer is the 2.73 gonna cut it with the 0.73:1 OD effectively giving me 1.99 final ratio with 255/70R15 tires. I am going to install an engine vacuum gauge to know when I should shift out of OD to get the best economy out of it. I know I may have to go up to a 3.42 gear which is just a tad higher gear than came in the 70's 12 bolt square body trucks 2.56 that Stewart has in his.
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i would love to find one of those 4 speed OD trannies. my burb only has the sm465 i haven't taken him on the interstate yet just been driving back roads if i want to go somewhere.
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Which trans is the better way to go?
My trucks if at all possible are manual transmissions. I understand manual transmissions and feel I can drive them efficiently and yield better MPG's. If it breaks I have another on a shelf with minimal down time. I also like the fun factor. My choice of this particular transmission is because it is an OD, was a factory option, and the previous owner already cut a hole in the floor because the original column (3 on the tree) was broken and parts were not available to fix it. I really like the uniqueness of 3 on the tree and I eventually found all the parts to put it back on the column but because the hole was already there and I had the transmission, the decision was easy. My hope is to get 20mpg with this set up. I have the tow and go cam so low end torque is better than a stock cam. The only question I have yet to answer is the 2.73 gonna cut it with the 0.73:1 OD effectively giving me 1.99 final ratio with 255/70R15 tires. I am going to install an engine vacuum gauge to know when I should shift out of OD to get the best economy out of it. I know I may have to go up to a 3.42 gear which is just a tad higher gear than came in the 70's 12 bolt square body trucks 2.56 that Stewart has in his.
With 235/75-15 tires, i turn 1800 at 55 and 2100 at 65. Now with this new converter i have (i swapped from 350C to regular 350 trans), if i'm on flat ground with light/cruising throttle, then the rpms are about the same as if i had lockup. If i start going up a hill or to pass, then the rpms do go up a little---200,300 rpms. Sometimes more if i really floor it.
If you have tow and go cam, maybe you can go down to 1400....lower, without lugging the engine?
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I am leaking fluid at the diff pinion seal and the manual trans output shaft seal. I have dropped the two piece driveshaft and have it on the bench. I want to replace the ujoints and the center support bearing. Can someone point me in the right direction on how to get the center support bearing off and the ujoints?
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Also, how to I know which 3 speed manual trans I have? There are two different seals as options to buy to replace.