# Should I convert to a manual trans?



## mehtwo (Nov 14, 2010)

My '86 Chevy ¾ ton transmission took a dump Friday. It has a TH400, I changed the filter last Saturday because reverse was having issues. Now it slips excessively in the 3 forward gears and reverse is just fine. Since I'm not really using this pickup for work right now, I thought about either 1.)rebuilding the existing TH400 trans, 2.)swapping in another TH400, or 3.)making a 4-speed (with a granny or compound 1st gear) pickup out of it. I have an '85 manual trans parts truck and all I'll have to do is replace the clutch, pressure plate, and throw-out bearing as well as the pilot bushing. Even the driveshaft will swap over.:thumbup: And yes this swap will use the hydraulic clutch setup. I wanted to do the 4-speed conversion before I got it on the road the first time, but I wanted to see how the TH400 trans would do. 

It has a 350 4-bolt main, 4.11:1 rear end with 89,7** original miles. What do you think? I plan on doing the conversion in a couple of weekends if I go the manual transmission route. I should be able to do this since this is a lot easier than what I've been doing to my '54 chevy project. Here's the pic of the culprit:


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## Randy Bush (Mar 7, 2011)

Being you have another truck to rob all the parts from guess it would not be to bad to do just time mostly. Lots of things to change around.


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## mehtwo (Nov 14, 2010)

Well if I rebuilt the TH400 myself that would be time as well, I'm still weighing out both options.


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## Randy Bush (Mar 7, 2011)

Me personally I would keep the auto. hanging pedels to change , steering colum , floor pan to change /modifiy , clutch master cyl to install. Seems to be a short life on that trany . Guess it is all in what you are wanting to get out of it.


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## mehtwo (Nov 14, 2010)

I don't think the filter was ever changed in its life....:whistling


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## Randy Bush (Mar 7, 2011)

That could for sure do it. Never much cared for the TH 400. Years ago when I was doing mechanic work I did replace them with 350. Now if you could figure out a way to put a C6 in there you would have a pretty bullet proof trany.:thumbsup:


Correction : was the TH700R4 that I did not care for.


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## bruces (Aug 19, 2012)

the th400 is a pretty easy and cheap tranny to rebuild yourself ,and cheap if a shop did it for you .


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## JT Wood (Dec 17, 2007)

I'd go th400:thumbsup:


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## mehtwo (Nov 14, 2010)

Randy Bush said:


> That could for sure do it. Never much cared for the TH 400. Years ago when I was doing mechanic work I did replace them with 350. Now if you could figure out a way to put a C6 in there you would have a pretty bullet proof trany.:thumbsup:
> 
> 
> Correction : was the TH700R4 that I did not care for.


The 700r4 was a weak contender, that's what I have in the ½ ton 'Burban. A C6 eh.....hmmmm....If I go that route I might as well replace the rest of the truck with Ford parts. I've always thought it would be cool to have a ¾ ton Ford with a 300 six and a 4-speed manual trans with a 4.10 rear end. I was especially fond of the 1980-1986 style even though the 1987-1996 would do. :thumbup:


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## hdavis (Feb 14, 2012)

Manual all the way:thumbsup:

And you already know why, so just do it.


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## mehtwo (Nov 14, 2010)

hdavis said:


> Manual all the way:thumbsup:
> 
> And you already know why, so just do it.


Can i ask, how old are you?


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## TimelessQuality (Sep 23, 2007)

I think I'd price a rebuilt 400... 

If it's outrageous, do the manual swap, otherwise, do the 2-3 hr replacement.

The manual job would be a lot of hours.


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## mehtwo (Nov 14, 2010)

I realize the time to do the conversion, I figured a couple of weekends at best. I think I'll sleep on it.....:yawn:


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## mehtwo (Nov 14, 2010)

I do appreciate the input, I'll know what decision to make by this weekend. :thumbsup:


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## hdavis (Feb 14, 2012)

mehtwo said:


> Can i ask, how old are you?


About as old as your picture - older than most on here. Had a F100 straight 6 three on the tree - great truck, would have been better with a 4 speed. 80s trucks with manual trannies are tough to find, I'm always looking for something older that can be restored. Salt / rust kills them up here.


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## mehtwo (Nov 14, 2010)

I'm 34 and when I was younger, i would have nothing but a manual trans. Since 2005 I've had a few auto pickups, but the manual trans still appeals to me...


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## hdavis (Feb 14, 2012)

mehtwo said:


> I do appreciate the input, I'll know what decision to make by this weekend. :thumbsup:


Maybe your tagline will help


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## woodchuck2 (Feb 27, 2008)

I myself would rebuild the TH400 and stuff it back in.

Bit off topic and coming from a ford guy but the TH400 is the strongest tranny out there from the big three back in those yrs. The TH400 from the diesel was the most preferred for drag racing, the sun gears were cut differently making them stronger. The TH400 also has more internal shaft supports than the C-6 and would hold up much better to tranny flexing and stress. The C-6 is also a great tranny and if i remember the AOD trannies were just as strong, in fact some internals from the AOD were used in the C-6 to change the gear ratio for 1st and 2nd for better launches and is why some drag racers would swap in the C-6 over the TH400.


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## ckcad (Oct 22, 2012)

woodchuck2 said:


> I myself would rebuild the TH400 and stuff it back in.
> 
> Bit off topic and coming from a ford guy but the TH400 is the strongest tranny out there from the big three back in those yrs. The TH400 from the diesel was the most preferred for drag racing, the sun gears were cut differently making them stronger. The TH400 also has more internal shaft supports than the C-6 and would hold up much better to tranny flexing and stress. The C-6 is also a great tranny and if i remember the AOD trannies were just as strong, in fact some internals from the AOD were used in the C-6 to change the gear ratio for 1st and 2nd for better launches and is why some drag racers would swap in the C-6 over the TH400.


What he said. Idk much about ford stuff but the th400 is a proven tranny.

To the op: do a rebuild on the 400 and dual feed the direct clutch. Also throw a th350 pump bearing and whatever spacers you need to get the proper end play and this will save you from thrust loading the case from the helical cut gears. This is part of the problem woodchuck2 is talking about. Throw a transgo kit in there while your at it. I think they might even make a dual feed kit for the 400 so u dont have to do any of the drilling etc. Don't drill the valve body hole to big though or you will defeat the purpose of a shift kit. And use bw high energy clutches. Make sure to flush your lines to with transmission line cleaner if u don't all the debris in there will cycle through your new build.


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## smalpierre (Jan 19, 2011)

Drop that turbo 400 back in there and be done with it in a weekend instead of jerking around with a manual shift conversion.

My thinking goes like this - if you want a manual tranny, get a truck that's equipped from the factory. Same goes for 4wd.

I want a crew cab 12v cummins 4x4 auto. I don't think they made them, so they're all conversions. To do this, I'll take a running 12v 4x4 auto, and a truck with a donor body and merge. No way I'd take my gas 2wd and try to convert to diesel 4x4.


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## mehtwo (Nov 14, 2010)

plummen said:


> Well is it running yet?



Yep, since this morning. After driving the 'burb all this time I'm sure going to miss the overdrive. :sad:


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## VinylHanger (Jul 14, 2011)

560 bucks? I couldn't even get a used junkyard one for that.

Yep, the lack of overdrive is annoying. It always feels like you need just one more gear. They are pretty bulletproof though.


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## woodchuck2 (Feb 27, 2008)

Too bad you did not live closer. I have been eye balling a CCLB dually from Cali that is for sale in Conn. Truck has no rust, 454/TH400 with a gear vendors overdrive. 6 new tires on Alcoa wheels and air bags in the rear. He just dropped the price to $2800. If i can get the money from customers i will buy it, yank the overdrive unit and air bags and resell it. Here is the link to the truck: http://glensfalls.craigslist.org/cto/3650359823.html 

They must be hard up because the price has dropped from $3500 since a couple days ago.


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## mehtwo (Nov 14, 2010)

woodchuck2 said:


> Too bad you did not live closer. I have been eye balling a CCLB dually from Cali that is for sale in Conn. Truck has no rust, 454/TH400 with a gear vendors overdrive. 6 new tires on Alcoa wheels and air bags in the rear. He just dropped the price to $2800. If i can get the money from customers i will buy it, yank the overdrive unit and air bags and resell it. Here is the link to the truck: http://glensfalls.craigslist.org/cto/3650359823.html
> 
> They must be hard up because the price has dropped from $3500 since a couple days ago.


In the future, I want to yank out the TH400 in my '86 dually and put a SM465 4-speed with a Gear Vendors Overdrive or a NV4500 5-speed. As for my '86 3/4 ton, I think I'll leave it alone.


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## SAW.co (Jan 2, 2011)

560 is good I spent a 'G' on rebuilding my 5 speed
Including clutch and all the perks.


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## Blast Off (Jul 15, 2012)

Something that seemed to be missed in this thread is that the crankshaft in your truck would very unlikely be machined for a pilot bearing. You would have to remove your crank and have the end machined to fit one, otherwise there is no way to center the clutch assembly. You can go from MT to AT without much trouble, going the other way is just not worth it unless it's a muscle car.


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## TimelessQuality (Sep 23, 2007)

I swapped in a manual for an auto on a 304 with no problem. I think the pilot was in the flywheel...


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## Randy Bush (Mar 7, 2011)

Blast Off said:


> Something that seemed to be missed in this thread is that the crankshaft in your truck would very unlikely be machined for a pilot bearing. You would have to remove your crank and have the end machined to fit one, otherwise there is no way to center the clutch assembly. You can go from MT to AT without much trouble, going the other way is just not worth it unless it's a muscle car.


This is not true on most older engines, can't think of one chevy or ford that was that way. Do believe there was a few dodge engine that way tho


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## Blast Off (Jul 15, 2012)

Randy Bush said:


> This is not true on most older engines, can't think of one chevy or ford that was that way. Do believe there was a few dodge engine that way tho


My bad then, most of my experience is Mopar and Olds which are typically not machined for pilot bushing unless it was a manual transmission car.


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## mehtwo (Nov 14, 2010)

Blast Off said:


> Something that seemed to be missed in this thread is that the crankshaft in your truck would very unlikely be machined for a pilot bearing. You would have to remove your crank and have the end machined to fit one, otherwise there is no way to center the clutch assembly. You can go from MT to AT without much trouble, going the other way is just not worth it unless it's a muscle car.


If you look closely enough, you will see it. Click on the bar above the pic for a bigger image. :thumbsup:


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