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Couple basic 205 questions :)

Russell

Russell

3/4 ton status
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Rocky View County, AB
Hey guys!

I've got my married SM465/NP205 combo just about ready to install here, but I've got a few basic questions to ask :)

1st, the combo came out of a 3/4 ton truck with 3.73 gears. The transfer case has one of those little reducer / accelerator thingers on the speedometer output. Since I've got a 3/4 ton with 4.10 gears, can I just remove that thing and call it good?

2nd, directly related to 1st, the little plastic gear inside of the case is apparantly shot, he gave me a new gear, but I haven't the foggiest how to install it, can anyone direct me to a link with some directions?

3rd, the shifter for the transfer case is very sloppy. I cannot really tell what gear is what, and both the shifter, and the little rod between the shifter arm and the transfercase are extremely sloppy. Is there a replaceable bushing a guy can buy for them?

4th, I want to ask a few questions about the operation of the transfercase. This is my first transfercase that a guy has to shift himself, everything else has been a push button type with automatic hubs. A guy cannot shift a 205 on the fly, correct? You have to come to a dead stop, then shift it, and continue in 4x4, right? Will I damage anything if I leave my hubs locked in while travelling on roads that are very slippery? I don't want to have to continually get in and out of the truck at stop signs if I cannot get the truck to move in 2wd.

5th, what is the maximum speed I am able to go in 4x4? Most of my driving is done on roads that are well travelled, and usually are pretty good. The speed limits on them are 50 mph, and I am wondering if I'd be pushing the 4x4 too hard if I put it into 4x4 to get up an icy hill or something, and didn't want to pull over to disengage the 4x4.

6th, when a guy disengages the 4x4, all you gotta do is stop, shift the transfercase, then unlock the hubs, correct? No backing up or anything required right? What is it when I hear about people having to back up to relieve binding or whatever?

Thanks for answering my seemingly extremely basic, and simple questions, but this is my first manual shift 4x4, and I don't wanna mess anything up, lol
 
You can leave you hubs locked while in 2WD, I do this during the winter and when I'm off-road heading to the wheeling spot, that way if I get a crazy idea and stuck myself before I even get where I'm supposed to be, I can kick it into 4WD.

Yes you need to be stopped to engage 4WD. Most transfer cases you can disengage from 4HI while driving. I did this often with my NP208 (feel free to correct if you can't with an NP205). Leaving the area I was wheeling in, I'd just kick the case out of 4HI into 2HI and drive to the car wash so I can spray out the underside of the truck, check for damage I didn't know about, and clean up the hubs so I can disengage them.

4HI, max I'd go is 35. Only instance that happens is if I'm on the back roads after a good rain, or there's heavy snow/ice. Logically you don't run 4WD on asphalt... bad idea.
 
Alright, it'd be great if I could just shift outta 4HI into 2HI without stopping. Only time I'll really badly need 4x4 is to get started off stop signs, cause everyone always spins their tires, and its next to impossible to get started without a 4x4, lol
 
you can use 4x4 hi at any speed not a good idea on dry pavement ok tho on snow/dirt/gravel
 
I just looked in the GM factory manual from my '79 with a SM465/NP205. There is NO RESTRICTION on driving speed in 4HI. In 4LO it says not to exceed 45MPH, probably just to keep you from blowing your engine.

The NP205 is a beastly transfercase, and you would be hardpressed to break it. It is this beefy because it is gear driven and very simple. The gears are not synchronized, which is why you have to stop to put it in gear, and it may help to give the clutch a little release or try to shift in that instant before the truck comes to a stop. Again, this is because it is gear driven, if the gears line up tooth to tooth it won't engage, just run into each other. You will find this happens similarly with the unsynchronized "LOW" gear in the 1st gear position on your SM465.

To get out of 4WD I usually have to back up. Do it in a straight line, slowly, while pushing on the transfer case lever for best results. There is no differential between the two axles like in a full-time 4WD transfer case. This causes binding and pressure on the drivetrain while driving in 4WD, and will make it difficult or impossible to shift out, without releasing the pressure (backing up). Have you ever "pennied" a door, where you push the top of the door in and stuff pennies in to put pressure on the bolt of the doorknob latch? It's like that. You won't budge it.

The SM465/NP205 combination is very strong, and you will most likely break everything else before this stuff starts to sweat. I run a built up 454, 40" Boggers, 14bFF rear end, and my transfer case and transmission are always happy. It is always good to drain it out and put synthetic or synthetic blend gear oil in it though, to increase life and lubrication.
 
Sorry I forgot to answer some of your questions.

You will damage nothing driving in 2WD with the hubs locked, besides your gas mileage (and actually the owner's manual insists you do this 10 miles per month to lubricate everything).

If you've always had automatic 4WD, this will be very new, and seem clumsy. When in 4WD, because of the binding I explained, your front end will "hop" when turning tight corners on pavement or high traction surfaces. This is normal and won't hurt anything except wear your tires more.

Yes, the transfer case shifter is wiggly. If you look under there and see the linkage you'll understand why. It has some play so that it can work the two independent shift rail as if they were one. I can never tell what I'm in either, I push it all the way to 4HI, and start counting clicks each time.

I forget what amount of change the speedometer adapter makes, but I severely doubt you'd just be able to remove it. Both sides of it are not the same thread either. To take it apart, just drill out the heads of the rivets and replace them with machine screws and nuts when you're done (use stainless steel).

Anything else?
 
Nope! That about covers it!

It looks like I'm gonna have to rebuild that 465 right away though. The PO told me it slipped outta gear sometimes, and yeah, I can see why, lol

The gear that is closest to the rear of the tranny up on the main shaft is very loose. It has some major play, and you cannot actually get the transmission into low gear without the gear impacting the reverse idler.

I've got a very nice 2wd 465, so I am hoping I'll be able to exhange gears between the two, and rebuild the tranny right away. Only thing I imagine I'd need would be new shift forks, cause while the 2wd tranny has some plastic material left on it, there is very little. The 4x4 shift forks are actually have the metal worn down too, no trace of plastic anywhere in there, and the metal is worn a good 1/16"

I suppose there is a possiblity I might need a new mainshaft too, assuming the 2wd and 4x4 mainshafts are different, and that there is a possiblity that this super loose gear may have damaged the mainshaft.
 
I just read some other stuff (the little owner's manuals from my '76 and '79 Blazers) and it says that theoretically you can shift from 2HI to 4HI and back at any speed, even with a NP205. So you may not damage it, but in practice it won't let you do it. But so I guess you don't have to worry about hurting anything.
 
The sun visor said the same thing about my NP208... it grinded when I tried to shift while rolling at 10 MPH. Never tried to go from 2HI to 4HI afterwards.

4HI to 2HI works at any speed though :)
 
If the hubs are locked it's easy to go from 2HI to 4HI and back with a 205. I've never had a problem doing it, even at up to 25 mph. Had it up to 55-60 mph in 4HI a few times, also no big deal. On snowy roads it'll disengage easily enough without backing up...I just lift my foot off the gas as I shift out of 4HI (while moving).


I think I'd probably just find another SM 465. They are a dime a dozen and it's pretty easy to find them in good shape.

Rene
 
Well, if I can find one for a dime, I'd gladly just get a used one, but we'll see if that is a possiblity, lol
 
tRustyK5 said:
If the hubs are locked it's easy to go from 2HI to 4HI and back with a 205. I've never had a problem doing it, even at up to 25 mph. Had it up to 55-60 mph in 4HI a few times, also no big deal. On snowy roads it'll disengage easily enough without backing up...I just lift my foot off the gas as I shift out of 4HI (while moving).


I think I'd probably just find another SM 465. They are a dime a dozen and it's pretty easy to find them in good shape.

Rene
Click to expand...

iirc, it's a 32 spline 465. Not very common.

For the people who say not to drive on pavement in 4Hi, have you ever done it? I've done it countless times with no problems. :confused:
Maybe if you have 3:73's up front and 4:56's in the back.
 
atho said:
iirc, it's a 32 spline 465. Not very common.

For the people who say not to drive on pavement in 4Hi, have you ever done it? I've done it countless times with no problems. :confused:
Maybe if you have 3:73's up front and 4:56's in the back.
Click to expand...

He said it came from a 3/4 ton truck. The only 32 spline 205's would have been in K30's as the 3/4 ton's got 208's in the time frame that 32 spline 465's were out. If it is a 32 spline 465/205 combo it almost certainly didn't come from a 3/4 ton.

My 'assumption' was that it was a 10 spline 465/205 as they did come in the pre-'81 3/4 tons and are pretty common.

I have driven on dry pavement in 4HI, and it's no fun in my truck. The manual tranny doesn't mitigate the bind very well and it just feels creepy. I know the weak link is the tires traction and that that's where the bind will release...it just feels wrong to do it. :crazy:

Rene
 
I'll backup what Rene said about shifting on the fly with the 205. I have shifted it from 2wd to 4HI while moving approximately 25-30 mph with no problems what so ever. The owners manual even states that you can shift into 4lo on the fly, but that you have to expect your RPM's to double. It is true that the 205 is unsychronized, but when the hubs are locked in, the front driveshaft is spinning the gear and 4wd engagement ring at the same speed so they just couple and uncouple very easily (maybe easier than setting still).

Also, the only time that you may need to back up only when unlocking the hubs. This helps to disengage them if they are in a bind .
 
tRustyK5 said:
He said it came from a 3/4 ton truck. The only 32 spline 205's would have been in K30's as the 3/4 ton's got 208's in the time frame that 32 spline 465's were out. If it is a 32 spline 465/205 combo it almost certainly didn't come from a 3/4 ton.

My 'assumption' was that it was a 10 spline 465/205 as they did come in the pre-'81 3/4 tons and are pretty common.

I have driven on dry pavement in 4HI, and it's no fun in my truck. The manual tranny doesn't mitigate the bind very well and it just feels creepy. I know the weak link is the tires traction and that that's where the bind will release...it just feels wrong to do it. :crazy:

Rene
Click to expand...

Good assumption, it is a 10 spline unit, sorry for not posting that earlier. My 32 spline case it a divorced unit, that will either eventually be put in with an NV4500, or be sold, and put a 208 doubler in for overdrive instead.

I know that the 10 spline unit is considered the weaker of the two, but I won't be bagging on mine on the trail, its a work truck / nice dd, not a trail beater, thats what the K5 will be for when I find one :)

Another question here. When I first got the tranny, I tried shifting it into all the gears, and rotated the input shaft, and output shaft on the transfercase. Everything shifted into gear ok, less not getting full engagement due to some seriously worn out shift forks, but nothing seemed to grind like it does when I am trying to shift it on the bench here. Does the adapter, or transfercase bolted to the back support the rear most gear on the output shaft somehow, or is it actually damaged and in need of replacement?

I know I can't use the output shaft from the 2wd, being a 35 spline output, but less the shaft itself, the rest of the materials should be the same right?

Will I have problems mix and matching gears from the two trannies? Only thing I'd need to fix that problem would be a new set of bearings, some gaskets, and a press right?
 
When I had mine out I noticed that it made a gear "grinding" noise when I rotated the output shaft. It was more like the gears were meshing, but not making very good contact.

In the truck no problems.

I believe both of the bearings on the rear receive some support (to stay in place) from the adapter.
 
Hmm, that'd make the most sense. Cause with that gear flopping around like that, I cannot possibly imagine that the PO wouldn't have noticed it. He just confirmed that less than the normal 2nd gear slip out, and occasionally first (both explained by the extremely worn out shift forks) that the transmission had no problems at all. It is only when I shift into low on the bench that I have any problems with the reverse idler striking the rear most gear.

I'll put the transfercase and adapter back onto the back of the transmission, and see if that helps me at all...

Also, what is the best detergent a guy can use to remove all of the gear lube from the inside of the case? I already drained it, pulled the filler, and drain plugs out, along with the PTO covers, and I was hoping there was some sort of a cleaner I could use to get all the black sludge out of the caseing, and all the grease off the outside of the casing, so I could paint it all before I put it into the truck.
 
well, I put the adapter and transfercase back on, still flops around. I'm thinking replacement may be cheaper than rebuilding, esspecially if I have to buy a press, and rent a bunch of funky tools.
 
Too bad, sorry to hear it.

I kept my eyes open for later trannies because of the fork wear issue. With the 10 spline stuff though you are out of luck unless you want to pull and swap stuff.

I've found later 465's for $50 from private individuals, difference is night and day between the '74 that was in there and the '85 I replaced it with. :)
 
Nothing to pull yet, hasn't even made it into my truck yet...

I can't seem to find any 4x4s around here. Lots of 2wd SM465s, dirt cheap, but not a single 4x4, either 10 or 32 spline...
 
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