Best combination for Highway Driving \transTcase

[roxxx]

I am gathering parts for my 4x4 short box
It has the the 4 speed with a 205 I plan on dropping in a nv4500 or 700r4
either way i am looking a lighter t case what would be the best combo ?

[obijuan]

you want an auto or a standard? either way you choose, 241 is the tcase of choice.

[snj8198]

Originally Posted by obijuan

you want an auto or a standard? either way you choose, 241 is the tcase of choice.

i agree, and since you already have the third peddle...

[franken]

In a 4x4 not sure why weight is a factor.
NV4500, 241 and 205 is magic.
I'm wondering about pushbuton 4x4 for lack of a better term.

[roxxx]

Originally Posted by franken

In a 4x4 not sure why weight is a factor.
NV4500, 241 and 205 is magic.
I'm wondering about pushbuton 4x4 for lack of a better term.

Not as in how heavy the t Case is just meant lighter Duty

[snj8198]

Personally i would look for an NV4500/241 combo and be done with it. I say this because a 6 bolt round pattern NP205 is very rare and an AA adapter to the 8 bolt 205 is getting way expensive:

http://www.advanceadapters.com/produ...kit-replsm465/

If the vehicle is being used for hill climbing, mudding or high horsepower wheeling where the drive train would see a lot of shock load then of course 205 is the way to go. But for daily driving, work, and heavy towing the 241 is plenty strong and capable and no expensive adapter. I've been finding them here for between $100-200. Since it would be out of the vehicle I would go through it with a master rebuild kit and slip yoke eliminator:

http://www.jbconversions.com/products/np241/rebuild.php

And if there is any other 241 parts you need:

http://www.nationaldrivetrain.com/transferlist.php

The only choice you need to make is whether you want to run a hydro or mechanical clutch. If you have the knowledge and capabilities run the hydro and get a good clutch.

[roxxx]

Originally Posted by snj8198

Personally i would look for an NV4500/241 combo and be done with it. I say this because a 6 bolt round pattern NP205 is very rare and an AA adapter to the 8 bolt 205 is getting way expensive:

http://www.advanceadapters.com/produ...kit-replsm465/

If the vehicle is being used for hill climbing, mudding or high horsepower wheeling where the drive train would see a lot of shock load then of course 205 is the way to go. But for daily driving, work, and heavy towing the 241 is plenty strong and capable and no expensive adapter. I've been finding them here for between $100-200. Since it would be out of the vehicle I would go through it with a master rebuild kit and slip yoke eliminator:

http://www.jbconversions.com/products/np241/rebuild.php

And if there is any other 241 parts you need:

http://www.nationaldrivetrain.com/transferlist.php

The only choice you need to make is whether you want to run a hydro or mechanical clutch. If you have the knowledge and capabilities run the hydro and get a good clutch.

Thank you
that's exactly what I am thinking, I wont be towing with it just highway and the odd off road trail creeping Great links to
now just gotta find the proper drop on the T-case

[snj8198]

They are easily found in the '88-'92 3/4 and 1 tons. Im not sure on the 1/2 tons. ask around here, perhaps someone will chime in on if the np241 was used behind the Getrag 5 speeds or not. If so then that opens up your search options.

[DirtyLarry]

I agree with obijuan and Steve, a 241 is a good choice. The best year to find is an ’88-’89 from behind a square body Blazer or Suburban with a TH400 or SM465 that way it will already have 32 splines and has a cable driven speedo. You will need a 32 spline tcase if you go the NV4500 route.

If you go the 700R4 route you will need a tcase with 27 splines from behind….well, a 700R4 or even a TH350. Don’t overlook 208 transfercases either as they are not that bad. From what I understand a 208 is basically the same as a 241 but without an internal oil pump.

I’ve done two NV4500 swaps, one with a NP205 and one with a 32 spline NP241. The 241 was the easiest as was a direct bolt on with no adapters needed. A 241 from anything else other than a '87-'91 square body will do you no good because the front drive shaft output will be on the wrong side....so don't bother pulling one from an IFS truck.

For my ’78 K10 I used the similar kit that Steve linked above but I would not recommend it. In fact, I am redoing my NV4500/205 combo right now to remove the figure 8 205 with the AA kit in favor of a round pattern 205. Long story as to why I am doing this but I will update me NV4500 swap thread once things really get moving.

Here is the 241 screwed onto the NV4500 in my Suburban.


Thread on the Burb…. The NV4500 swap is on page 5

[roxxx]

Originally Posted by DirtyLarry

I agree with obijuan and Steve, a 241 is a good choice. The best year to find is an ’88-’89 from behind a square body Blazer or Suburban with a TH400 or SM465 that way it will already have 32 splines and has a cable driven speedo. You will need a 32 spline tcase if you go the NV4500 route.

If you go the 700R4 route you will need a tcase with 27 splines from behind….well, a 700R4 or even a TH350. Don’t overlook 208 transfercases either as they are not that bad. From what I understand a 208 is basically the same as a 241 but without an internal oil pump.

I’ve done two NV4500 swaps, one with a NP205 and one with a 32 spline NP241. The 241 was the easiest as was a direct bolt on with no adapters needed. A 241 from anything else other than a '87-'91 square body will do you no good because the front drive shaft output will be on the wrong side....so don't bother pulling one from an IFS truck.

For my ’78 K10 I used the similar kit that Steve linked above but I would not recommend it. In fact, I am redoing my NV4500/205 combo right now to remove the figure 8 205 with the AA kit in favor of a round pattern 205. Long story as to why I am doing this but I will update me NV4500 swap thread once things really get moving.

Here is the 241 screwed onto the NV4500 in my Suburban.


Thread on the Burb…. The NV4500 swap is on page 5

Thank you

[argonaut]

Originally Posted by DirtyLarry

For my ’78 K10 I used the similar kit that Steve linked above but I would not recommend it. In fact, I am redoing my NV4500/205 combo right now to remove the figure 8 205 with the AA kit in favor of a round pattern 205. Long story as to why I am doing this but I will update me NV4500 swap thread once things really get moving.

Larry,
I am curious to see your story as to why you are ditching the AA kit, and also your method for using the round pattern NP205.

I myself opted not to go with the AA kit for my figure 8 NP205 after studying the schematic;nIstead I picked up a round pattern NP205 with plans to do some minor machining and reinforcing to the stock NV4500 adapter.

Sorry if I'm thread jacking. I didn't realize and early NP241 would bolt up without any mods. I may look at that option also. I'm curious to see what total length is with the NP241 versus the NP205 mated direct like I'm planning.

[obijuan]

for a round pattern 205 to the nv4500 you just swap out input gears in the 205. there are two types. the short input is 32 spline from 1984 and older. the longer input gear is exclusive to the round pattern. shortening the input gear basically elminates the need for the AA spacer, however clearance is needed for the shift rail. little bit of fancy grinder work and it will be just fine.

and you cant just cut down the long input gear.

a 241 is a direct bolt up, and are you using the stock tcase or has it been slip yoke eliminated?

[DirtyLarry]

Well, if you recall I wasn’t real thrilled to use the figure 8 205 in the first place with the AA kit but I could not find a round pattern 205 at that time. All the round 205’s were going for huge money, if you could find one, so I settled on the 27-0031 AA kit and a figure 8 27 spline 205. That kit requires the rear of the NV4500 mainshaft to be hacked off just behind the large 31 spline cog (I think that 31 spline cog is for a damper on some vehicles that use one). In any event, by cutting off the tailend of the mainshaft you do away with the nut that is famous for coming loose causing the 5 gear problems. AA’s answer to hold 5th in place after the tail is cut off by using a bolt together collar.

My first NV4500 lasted 200 miles (one trip to Denver and back), which was no surprise as I got it used knowing it had an issue. We found that one had the 5th gear nut backed off but hoped by tightening it by way of the AA kit that would resolve that transmissions problem….nope, the damage was too bad. So, I got another NV4500. The second one was not a reman, but a BRAND NEW 2006 Silverado NOS transmission. I’ve been running that one now for close to 20,000 miles and 5th gear is screaming just like the typical NV4500’s that have 5th gear problems when the nut comes loose allowing the 5th gear to knurl the mainshaft.

It is my personal opinion that the AA kit 27-0031 which requires the tailend of the mainshaft to be cut off then uses a bolt on collar to hold 5th gear in place does not hold it tight enough, just like if the nut was loose. I spoke to AA and they say I am full of hot air. Okay, maybe I am but I am not going to toast another NV4500 with their questionable kit.

That said, I am using a 1985 round pattern 205 I bought from member Ryanroo this past spring. This 1985 205 has a slip yoke and the long 32 spline input. I have a short 32 spline input on the way to me from ORD as we speak and I am using the rear portion from a different 205 to convert it to a fixed yoke. It is getting treated to all new bearings and seals while it is in pieces right now. Not using any adapter between the NV4500 and this 205. Basically, it will be bolted together just like now the NV4500 and 241 are in my burb.

I also have a new mainshaft, 5th gear, nut, etc. to have installed in my NV4500 so I can screw this all together the way I should have done it 3 years ago.

This is how it looked the other day after I gutted it in preparated for sand blasting. It’s all painted now just waiting to go back together once the short 32 spline input and modified shift rails arrive. You can see the long 32 spline input gear over there close to the Super Swamper.



The NV4500/32 spline 241 in my Burb was a piece of cake. It was a complete bolt for bolt swap where only cutting the trans tunnel required any real creativity. Even the transmission crossmember went back into the same exact location. The drive shafts didn’t need to be tweaked either. Someday I may to a SYE on it but, it is more of a cruiser /light wheeler. Don’t really feel a SYE is really needed on it.

[argonaut]

Basically you need to do three modifications to the stock NV4500 4wd adapter to work with a round pattern NP205 with a short 32-spline input shaft swapped in:

1) notch the mating flange at the 3-o-clock position to provide clearance for the rear output shift rail on the NP205
2) bore the female pilot area inside the mating flange another ~1/4" deep to clear the NP205 input seal housing.
3) notch a small relief at the mating flange to provide clearance for the idler shaft nut

So far I think that is it. I'm also planning on fabricating some sort of steel brace on top of the adapter that will bolt between the flanges, at the existing bolting locations, to carry a portion of the tension load of the heavy NP205 directly from the transfer case housing to the transmission housing.

Then again I'm not sure what the weight differences is between say a NP241 or NP208 and the NP205. Need to look that up.


I decided against the AA adapter because I want to retain the factory damper, which guarantees 5th gear retention. And I'd rather not have another adapter sleeve with external seal and internal sealing RTV all of which is susceptible to failure sooner or later.

[snj8198]

Originally Posted by argonaut

Basically you need to do three modifications to the stock NV4500 4wd adapter to work with a round pattern NP205 with a short 32-spline input shaft swapped in:

1) notch the mating flange at the 3-o-clock position to provide clearance for the rear output shift rail on the NP205
2) bore the female pilot area inside the mating flange another ~1/4" deep to clear the NP205 input seal housing.
3) notch a small relief at the mating flange to provide clearance for the idler shaft nut

So far I think that is it. I'm also planning on fabricating some sort of steel brace on top of the adapter that will bolt between the flanges, at the existing bolting locations, to carry a portion of the tension load of the heavy NP205 directly from the transfer case housing to the transmission housing.

Then again I'm not sure what the weight differences is between say a NP241 or NP208 and the NP205. Need to look that up.


I decided against the AA adapter because I want to retain the factory damper, which guarantees 5th gear retention. And I'd rather not have another adapter sleeve with external seal and internal sealing RTV all of which is susceptible to failure sooner or later.

Hi Argonaut,

I have a round pattern 205 direct mounted with a 32 spline short shaft. Im curious why i didn't run into steps 2 and 3 as you explained.

[argonaut]

Originally Posted by snj8198

Hi Argonaut,

I have a round pattern 205 direct mounted with a 32 spline short shaft. Im curious why i didn't run into steps 2 and 3 as you explained.

It would be great if they are unnecessary. Do you have any photos of your installation?

[DirtyLarry]

Originally Posted by argonaut

Basically you need to do three modifications to the stock NV4500 4wd adapter to work with a round pattern NP205 with a short 32-spline input shaft swapped in:

1) notch the mating flange at the 3-o-clock position to provide clearance for the rear output shift rail on the NP205
2) bore the female pilot area inside the mating flange another ~1/4" deep to clear the NP205 input seal housing.
3) notch a small relief at the mating flange to provide clearance for the idler shaft nut

So I wrapped up the round pattern 205 rebuilt last night and snapped some pictures.

Jason is correct on 1 and 3. Not sure about 2 yet until I get 1 and 3 done.

Here are some pictures of what needs to be modified per Jason’s 1 and 3 for a round 205 with a short 32 spline input to be bolted to a NV4500.








I mic’d the bearing retainer and retainer recess in the NV4500 cover and it appears it will be direct fit. Won’t know for sure until after I modify the rear cover for the shift rod and idler nut clearance.


Beauty shots of the freshly rebuilt round 205. I put all new bearings, seals, new speedo gear, new ORD shift rails with the front wheel drove mod and converted it from a slip yoke to a fixed yoke using pieces from one of the other 205’s I had laying around.




I hope to have time to start modifying the NV4500 rear cover later tonight or tomorrow night. I'll keep ya'll posted.

Wow, we really got off topic on Roxxx’s thread but I guess this was something we were all curious about . I’ll update my NV4500 thread once I get thrashing on the truck itself. Probably won’t be until after Christmas.

As far as Roxxx goes....a NP241 or 208 would still be the best for a driver/moderate offroadster.

[obijuan]

You sure about 2 and 3?

[DirtyLarry]

Originally Posted by obijuan

You sure about 2 and 3?

I’m wondering the same thing. Never heard of either. Guess, I’ll find out in a few weeks when I go back together with my round 205 with a short 32 spline input to a 4500.

[argonaut]

Well thats based on my research. I've seen a few examples of this done with drivers drop units using the didge adapter but only actually seen photo proof of one person do what we are proposing here. I'll take a few measurements when I het home tonight and verify.

[snj8198]

No, i didn't document it. I purchased the trans new in a complete package deal along with an aftermarket round pattern empty t-case shell from GearTechHD. Perhaps these mods were already done with me not even knowing.

[obijuan]

for what its worth, the gm203 uses the same size input seal retainer as the 205. i bolted up a 203 range box directly to my nv4500.

well after i redrilled the face to round pattern that is.

[argonaut]

DirtyLarry,
Thanks for the photos and confirmations. Regarding item 2, from my caliper measurements the bore diameters match but the concern is that the depth of the bore in the adapter is not quite deep enough for the seal retainer. Although there is some taper to the retainer. I'll wait to see what you discover since you are moving so much faster than I am!

[duallyjams]

NP241 would be the easiest but for what ever reason they are hard to come by in my area.

[roxxx]

Originally Posted by duallyjams

NP241 would be the easiest but for what ever reason they are hard to come by in my area.

Same here hard to find so far with the right drop