6.2 TH400/Np208 To SM465/NP205 Swap Questions? Opinions?

[KSSIII]

If everything goes as planned I'll have a 4 speed swapped in my M1009, but I'm a mechanical novice. So It would help a lot to get some second opinions on my plans.

The Truck-
1985 M1009 6.2 Diesel, Shot TH400/Np208, 10 bolt axels 3.08:1 gears 33in tires

Possible Donor truck Candidate- 750$
1979 chevy K10 Scotsdale- 12 bolt rear axle, dana 44 front axle, NP465/205 combo 4 wheel drive, manual trans 350 V8 143900 Miles

I hope I'll find most of the things I need for the swap in the truck.

I under stand I might need
-Flywheel (dual mass? Single mass?)
-Clutch stuff?
-custom made drive shafts?

anything else i'm missing?
would there be a more ideal candidate, that is someone cheap or common?

I might do a NV4500/3500 swap down the road, but for now regarding difficulty level, and budget I gotta go with the Sm465

I plan on daily driving this truck, highway, freeway, city all that jazz, and maybe some occasional off-road.
I'm curious on how everyone feels about this combination 6.2/SM465/3.08/33in tires or close. How do you feel about it for daily driver purposes. Are you able to maintain Mpgs over 20? are you able to keep Safe RPMS over 70?

Thanks Guys

 

[Blazooki]

If all your gonna do is daily drive the truck and occasionally take it off road, then take the $750 you were gonna spend on the K10, buy a rebuilt T400. install and be done. If your thinking the SM465 is gonna be better its not. Its just gonna be different. your doing a ton of work to trade red apples for green apples. no matter what you do your not gonna reliably get over 20 mpg and go faster than 70 mph in a stock 6.2 and a transmission with no overdrive gear. whether its a t400 or a sm465. If you do buy the K10 then I'd swap the axles too. a 6.2/465/205 is gonna wreck those 10 bolts. remember a sm465 isn't a 4 speed. its a 3 speed with a granny first. A 465/205 is way heavier than a t400/208 so your adding a bunch of extra mass to the drive train. The built in cushion you get from a auto trannny and chain T-case is gonna be gone once you go to all gears. and all that torque is going directly into those tiny 10 bolt gears and axle shafts.

 

[obijuank5]

It's going to drive exactly the same. But it will be way more fun to row the gears in a naturally aspirated diesel. I'd swap it because a th400 is a power sucking floor heater.

 

[KSSIII]

It's going to drive exactly the same. But it will be way more fun to row the gears in a naturally aspirated diesel. I'd swap it because a th400 is a power sucking floor heater.

That is exactly my point and if it drives the same I can live with it.

 

[KSSIII]

If all your gonna do is daily drive the truck and occasionally take it off road, then take the $750 you were gonna spend on the K10, buy a rebuilt T400. install and be done. If your thinking the SM465 is gonna be better its not. Its just gonna be different. your doing a ton of work to trade red apples for green apples. no matter what you do your not gonna reliably get over 20 mpg and go faster than 70 mph in a stock 6.2 and a transmission with no overdrive gear. whether its a t400 or a sm465. If you do buy the K10 then I'd swap the axles too. a 6.2/465/205 is gonna wreck those 10 bolts. remember a sm465 isn't a 4 speed. its a 3 speed with a granny first. A 465/205 is way heavier than a t400/208 so your adding a bunch of extra mass to the drive train. The built in cushion you get from a auto trannny and chain T-case is gonna be gone once you go to all gears. and all that torque is going directly into those tiny 10 bolt gears and axle shafts.

To my the standard shift conversion is worth the work if it will drive the same, or better. there's just a whole different feel to a standard shift diesel I miss driving. If I get the K10, I'm considering swapping the axels, but wouldn't it make the car slower and decrease the top speed?

 

[obijuank5]

That truck could potentially have 3.08 gears as well.
Numerically higher (lower ratio)gears will make the truck slower top speed.

Use the calculator at grimmjeeper.com to come to your drivability conclusion and what you consider safe rpm

 

[KSSIII]

That truck could potentially have 3.08 gears as well.
Numerically higher (lower ratio)gears will make the truck slower top speed.

Use the calculator at grimmjeeper.com to come to your drivability conclusion and what you consider safe rpm

In that case, hell yeah

 

[campfire]

First, welcome to CK5. I'm glad to see another member who appreciates the concept of "winter."

Second, read my M1009 thread, I'm doing an TH400-->NV4500 conversion on it right now (link in my signature line).

Third, look up @Richcz28's M1009 thread, he did the TH400-->SM465 swap and has much insight on the swap and its downsides. Link here.

 

[diesel4me]

The flywheel off a gas engine will not work on a 6.2,it "might" bolt up,but the diesels are externally balanced...and the only gas ones that are externally balanced are 400 small blocks and 454's,and both are different than the diesels are..a diesel flywheel for a manual trans is pretty hard to find used and quite expensive new--the dual mass ones are known to be failure prone also..

I swapped a SM465 into my '72 K5 ,that formerly had a TH350/NP205,and it was a week of after work six pm to midnight "shifts" of hard work,to get the pedals in,the tranny,etc,and in the end I hated it--the 3:08 gearing sucked with a SM465,the gear spacing on them is poor,and I regretted doing the swap even mare after a few months and 2 rebuilt pressure plates failed--after installing the third clutch,a diaphram Hayes one instead of the sucky 3 fingered 12" Borg-Warner ones,I swore if it ever gave me trouble again,it was going up for sale..

The TH350 might be a bit weak for a 4x4 used to plow or tow,and a TH400 is kind of a power sucker,especially behind a diesel,but I prefer an automatic for plowing and general "around town" driving..

If I wanted a manual transmission again I think it would be better to just find another truck that has one factory and buy it..it is a lot more involved doing a swap than it appears..its best to have a complete donor truck with the exact parts you need..

 

[campfire]

The SM465 and NV4500 both have a wide gear spacing, and the granny gears make them really 3 and 4 speed transmissions instead of 4 and 5 speeds. Mileage-wise, 20MPG is possible on the highway, but if you want 23-25MPG, grab overdrive while you have a chance. If you're determined to have a manual, the SM465 should be a pretty straightforward swap. Measure the tranny/t-case length ahead of time. It's possible for your new drivetrain to have the same length as your current one (so no driveshaft mods will be necessary ). That makes the swap more fun. But it's also possible for them to not match, so take your measurements ahead of time.


Gearing-wise, I whipped up an excel spreadsheet to allow me to tweak and graph the numbers, because I like doing that. It has come in handy many times. Here are a couple of my rigs, to give you some real-world data points.

 

[campfire]

Flywheel-wise, you need a 6.2/6.5 diesel flywheel (the engine is externally balanced). An SBC flywheel will bolt up but will not balance the engine. Avoid the dual-mass flywheels like the plague, they were a crummy idea when they were new, and GM abandoned the idea after just a few years. All 6.2 engines got single-mass flywheels, and most of the 6.5s did too.

Clutch-wise, the '78 mechanical linkage can be used in your truck, although many folks prefer the hydraulic system that came out in '86 (less fiddling and tuning required). If you ever plan on running an NV4500 or NV3500, go hydraulic now, it will be more fun to set up and the newer transmissions are not set up for mechanical linkages. @Chevy305 did break the rules with a custom bell housing, but IMO it's neither easier nor cheaper than simply running hydraulic if you're starting with an automatic).

Measure 6 times, cut once. If you have no other reason to modify the drivelines, I would specifically measure the length of your current setup and take care to match it. I can say that an NV4500 is within 3/8" of the TH400 you're taking out, length-wise. Exact numbers are in my thread, but IIRC it's about 27.5" from the back of the engine block to the front of my NP208. SM465 cases are not all the same, measure the one you're thinking of buying before you pull the trigger. And being an older tranny with an NP205, the figure-8 output bolt pattern won't match the 6-bolt pattern you currently have, so you'll hafta replace both the tranny and T-case together. Be sure to account for this when you measure the total length.

The short answer is that yes, you can do this, and it has been done many times. And there are lots of folks here who can answer questions. Since mine is currently torn apart, it's pretty easy for me to grab a measurement if you need one.

 

[campfire]

I swapped a SM465 into my '72 K5 ,that formerly had a TH350/NP205,and it was a week of after work six pm to midnight "shifts" of hard work,to get the pedals in,the tranny,etc,and in the end I hated it

It is a pile of work, but it's doable. Pulling the pedals is no fun, everyone seems to agree on that. But it shouldn't be more than an evening or two of your time at worst. You'll prolly spend more time setting up the linkage than you will swapping the nasty pedal bracket.

 

[campfire]

Oh - if you still have your stock 24V starter, you will hafta grind down the nose to gain clearance when you switch to the flywheel. This is super easy, but it's something that I wound up learning the hard way (). GM shipped these engines with transmission-dependent starters. Since ALL CUCVs are automatics, there are no 24V manual starters. If you go buy a 12V replacement from Autozone, they probably only stock the open-nose manual style, as they fit either type of rig. But the starter you have will not fit in its stock form. Pictures in my thread. Read through my thread and Rich's thread before you throw money down on this idea, it's good to know what you're getting into ahead of time. Ask me how I know.

 

[diesel4me]

In my case I had to swap the steering colum and the power brake booster at the same time as installing the pedals (tilt wheel was flopping,and the booster was bad)--so that doubled the agony of lying under the dash for two nights all by itself..

I would probably never attempt another manual swap from an automatic today,being "too old" and phisically un-fit to complete the task...but going from manual to automatic would be easier and make the truck easier to drive in the long run,I might be able to pull off that type of a swap..(but if I had a truck with a manual trans I wouldn't want to get rid of it probably either,I'd live with it being harder to plow with and drive in city traffic)..

 

[campfire]

In my case I had to swap the steering colum and the power brake booster at the same time as installing the pedals (tilt wheel was flopping,and the booster was bad)--so that doubled the agony of lying under the dash for two nights all by itself..

I would probably never attempt another manual swap from an automatic today,being "too old" and phisically un-fit to complete the task...but going from manual to automatic would be easier and make the truck easier to drive in the long run,I might be able to pull off that type of a swap..(but if I had a truck with a manual trans I wouldn't want to get rid of it probably either,I'd live with it being harder to plow with and drive in city traffic)..

Yeah, there's a big gap between "I want a manual tranny" and "I'm willing to put in all the time, work, and money required to make a manual tranny appear in an automatic truck."

 

[KSSIII]

The flywheel off a gas engine will not work on a 6.2,it "might" bolt up,but the diesels are externally balanced...and the only gas ones that are externally balanced are 400 small blocks and 454's,and both are different than the diesels are..a diesel flywheel for a manual trans is pretty hard to find used and quite expensive new--the dual mass ones are known to be failure prone also..

I swapped a SM465 into my '72 K5 ,that formerly had a TH350/NP205,and it was a week of after work six pm to midnight "shifts" of hard work,to get the pedals in,the tranny,etc,and in the end I hated it--the 3:08 gearing sucked with a SM465,the gear spacing on them is poor,and I regretted doing the swap even mare after a few months and 2 rebuilt pressure plates failed--after installing the third clutch,a diaphram Hayes one instead of the sucky 3 fingered 12" Borg-Warner ones,I swore if it ever gave me trouble again,it was going up for sale..

The TH350 might be a bit weak for a 4x4 used to plow or tow,and a TH400 is kind of a power sucker,especially behind a diesel,but I prefer an automatic for plowing and general "around town" driving..

If I wanted a manual transmission again I think it would be better to just find another truck that has one factory and buy it..it is a lot more involved doing a swap than it appears..its best to have a complete donor truck with the exact parts you need..[/QUOTE]

Thank you for you input, I do plan on getting a donor truck - 1979 chevy K10 Scotsdale with a 465/205. I plan on ordering a one Singlemass 6.2 flywheel online, and I'm considering swapping the axels out that truck too. I'm sorry to hear you had a bad time with your swap, I guess i could avoid some trouble by getting a hayes diaphram instead of the borg-wagner diaphrams.

 

[KSSIII]

Yeah, there's a big gap between "I want a manual tranny" and "I'm willing to put in all the time, work, and money required to make a manual tranny appear in an automatic truck."

Thankyou for the sources I will check them out.
I'm pretty set on swaping in the sm465 since it will be less of a hassle, and I've already found a decent donor truck Just gotta get the parts together and make sure I don't screw up.

To clairfy
-I'll bolt up the clutch pedals and mechanisms either mechanical, or a hydrallic one if I can find a donor after 85. that should bolt on directly
-I will order a Single mass Flywheel for a 6.2 manual
?-will I be able to use the same clutch disc/cover and other components?
-Then bolt the bellhousing/tranny/transfercase as a single unit.
?- then the only issues I need to face is the crossmember for the tranny, and drive shaft lenghts correct?

Thankyou for all the helpful information

 

[obijuank5]

M1009 crossmember is the same as the 79. May need to move it to a forward set of holes that are probably there. Shifter holes are not the same. Swap trans humps. Then shafts need built.

Just thought you will be swapping vacuum boost brake pedals to a hydro boost system. You'll need to look into the differences at the pedals between the two. Vac pedals can be made to work on hydroboost. Don't know what it takes though.

 

[campfire]

I plan on daily driving this truck, highway, freeway, city all that jazz, and maybe some occasional off-road.
I'm curious on how everyone feels about this combination 6.2/SM465/3.08/33in tires or close. How do you feel about it for daily driver purposes. Are you able to maintain Mpgs over 20? are you able to keep Safe RPMS over 70?

Thanks Guys

I missed this 33" question earlier. That gear combination will actually be pretty good on the road. The 3.08 gears will cover for the lack of O/D. You'll still have the 3.5-speed transmission, but aside from the wide splits it will be more streetable that it was with the stock 31s. Having lockup on the highway (unlike the TH400), I'd expect mileage above 20MPG if you're a gentle driver.




FWIW, my K10 (shown above) is geared quite a bit more anemically than this, and it will hold highway speed fine. It's not a great tow rig, but it handles driving quite well. I'd actually consider this gearing a little on the torquey side for a street cruiser (the rule of thumb is to cruise at 1800RPM for efficiency, which would make this a 55MPH truck). But you'll be just fine at 75MPH with this combination, gearing-wise. Even 80MPH is only 2500RPM. That's high enough to sound like it's screaming if your exhaust is shot, but it's not a problem aside from the noise.


FWIW, when the K10 is cruising unloaded it hasn't ever gotten less than 21MPG, so it is possible if that's your goal.

 

[KSSIII]

I missed this 33" question earlier. That gear combination will actually be pretty good on the road. The 3.08 gears will cover for the lack of O/D. You'll still have the 3.5-speed transmission, but aside from the wide splits it will be more streetable that it was with the stock 31s. Having lockup on the highway (unlike the TH400), I'd expect mileage above 20MPG if you're a gentle driver.


View attachment 216565

FWIW, my K10 (shown above) is geared quite a bit more anemically than this, and it will hold highway speed fine. It's not a great tow rig, but it handles driving quite well. I'd actually consider this gearing a little on the torquey side for a street cruiser (the rule of thumb is to cruise at 1800RPM for efficiency, which would make this a 55MPH truck). But you'll be just fine at 75MPH with this combination, gearing-wise. Even 80MPH is only 2500RPM. That's high enough to sound like it's screaming if your exhaust is shot, but it's not a problem aside from the noise.


FWIW, when the K10 is cruising unloaded it hasn't ever gotten less than 21MPG, so it is possible if that's your goal.

Awesome! thats great to hear Hopefully I'll get the donor by the end of this next week. but I cant see any pictures youve posted, I click them and they bring me to an error page