Click for Coverage
Due to the EU’s Global Data Protection Regulation, our website is currently unavailable to visitors from most European countries. We apologize for this inconvenience and encourage you to visit for the latest on new cars, car reviews and news, concept cars and auto show coverage, awards and much more.MOTORTREND.COM
  • JP Magazine
  • Dirt Sports + Off-Road
  • 4-Wheel & Off-Road
  • Four Wheeler

August 2009 4x4 Truck Repair Questions - Techline

Posted in How To: Tech Qa on August 1, 2009
Share this

Where To Write
Address your correspondence to:
Four Wheeler
6420 Wilshire Blvd.
Los Angeles, CA 90048.

You can also reach us by e-mail at; be sure to type the words "Tech Line" in the subject line. All submissions become the property of Four Wheeler, and we reserve the right to edit them for length, accuracy, and clarity. The editorial department also can be reached through the Web site at Due to the volume of mail, electronic and otherwise, we cannot respond to every reader, but we do read everything.

Late-Model S-Blazer T-Case Options
Question: On my 2000 S-10 Blazer, the pushbutton 4x4 is the most unreliable system I have found yet. Is there a conversion kit to bypass the pushbutton? Maybe a floor shift, like the older S-10s? Will the transfer case out of the older models bolt up to the 2000 that I have? My Blazer is completely stock--no mods yet until I know what I can do about this first.
Kris Batten
Bellville, OH

Answer: From what I can tell, you either have an NV236 or a NV233 transfer case. The NV236 is an electronic-shift transfer case with three drive ranges. Shifting from rear-wheel drive to four-wheel drive is done automatically when the shift control module receives wheelslip information from the speed sensors. The shift control module then engages the transfer case motor/encoder to engage the front axle and 4-Hi range. When the shift control module receives information that the wheel rotation is the same on both axles, the transfer case shift control module sends position information to the motor/encoder to take it out of four-wheel drive. You can also electronically select the three drive ranges of 2-Hi, 4-Hi, and 4-Lo.

The NV233 is also an electronic-shift case, offering the same three modes of operation as the NV236, but without the speed sensors to engage the front axle when slippage is detected.

Prior to 1998 or so, the S-10s came with either the electric-shift NV233 or the manual-shift NV231. My guess is that they are really close cousins. There are a lot of interchangeable parts on some of the 200-series cases, but no, you can't put the mechanical shift linkage onto the electric-shift case. Again, it's just a guess, but the 231 from the earlier S-10 should just bolt right up. There may be some rear driveshaft length issues to be dealt with.

The NV231 is a pretty common transfer case used by both GM and Jeep for lots of years. Will the Jeep case work? Maybe or maybe not. The NV231 as used in Jeep vehicles has come with three different spline counts on the female drive gear and had at least three different lengths, depending on the length and spline count of the transmission male spline output shaft.

This could also be very true with the spline count/shaft length on the S-10. But it seems that Chevy has been a bit more consistent than Jeep, so I'm betting you could find a NV231 out of an early S-10 and just bolt it in. Naturally, you'll need the proper shift linkage to go with it. One problem may develop if it's an NV236; you may get a "check engine"-type warning light and a trouble code indicating something wrong in that the speed sensor won't be sending the proper message to the transfer-case control module. I really don't know what to tell you to do about this. Maybe some electronic whiz at a Chevy dealer can figure out how to fool it.

NP 203/205 Swap For K-Blazer
Question: I have a '78 K5 Blazer with a Turbo 350 with an NP203 transfer case. I would like to put my NP205 that came out of a '73 with the four-speed instead. What options do I have when this time comes?
Keith Hepburn
Leiston, ID

Answer: Your present 203 transfer case has a 27-spline gear, while the 205 out of the '73 Blazer with the SM465 four-speed has a 10-spline female input gear. The bolt pattern between the two, I also believe, is different. Yep, to say it simply, they don't match up.

I think that you have a couple of ways to go. Advance Adapters ( offers a special adapter to make this conversion. Another choice would be is that I believe 205s behind the TH350 automatics had the right spline count, so maybe you might want to consider doing some trading.

Another idea, and a great one at that, is to retain your present 203 and combine it with the 205. This will allow you to have a 2:1 or a 4:1 low range. The people to talk to about this are Off Road Design ( A drawback to this is that you have to convert your 10-spline 205 to a 32-spline gear. They can offer you the parts to do this. Believe it or not, the "Doubler", due to the design, is actually the same length as the factory 203 setup as you're only using the gear reduction unit of the 203 'case.

Overlooked Trail Tool?
Question: Regarding your Workbench on "Trail Tools That You Need" (April '09): Although maybe not really a "tool" in a sense, I consider a roll of toilet paper quite the essential, as opposed to rocks or tree branches. Just a little something to add to your list.
Ray Kendrick
Tucson, AZ

Answer: What?! Do you think that the members of the "Corps of Discovery" (sometimes called the Lewis and Clark expedition), carried a few cases of toilet paper along with them? Come on, tough it out, man.

But you're so right--rocks, pine needles and such really don't work that well, while the leaf of the mullein plant (I have been told) is soft and does a good job. (Now if I just could always find that plant when we need it!) My wife is my best friend and we are always together, plus we raised three daughters who learned to squat behind a bush before being toilet-trained. You think that they could live without TP? There is always a roll of TP in our vehicles--and actually, we have a special waterproof pouch to carry it in, and then some smaller portions of a roll in several other hidden-away spots. Oh, and in a pinch, it also makes for a fire-starter, and when used with duct tape, makes for a nice bandage. Good stuff to have--thanks for the reminder.

Tranny Rebuild Tip For Young Wrench
Question: I'm a 17-year-old student trying to rebuild my 1991 Ford Bronco Eddie Bauer Edition. I need a transmission, but every time I try to find one, it doesn't work. I would appreciate it if you would contact me if you know where I could find one.
Jonathan Mize
Odenville, AL

Answer: I can understand how frustrating it must be to a 17-year-old to put in a used transmission and find that it doesn't work. It would piss me off at my old age even more! My suggestion is that you save up some money and head for your local transmission rebuilder. Remember, you get what you pay for! Ask around at the local repair garages where they get their transmissions from. Not all rebuilds are the same.

Letter Of The Month
Detroit On Ice: Safe, Or A Handful?
Question: I got a line on a Detroit Locker that hasn't seen much use for $300 bucks. Are they as much of a terror on the ice as everybody thinks? I drive so slow in the winter with my Toyota, so I don't think I'll have problems, and I use four-wheel drive whenever possible. I only have 33-inch tires. Seemed better than buying a lunchbox locker Are the handling problems mostly encountered when cornering? What has been your experience with the Detroits?
Derek Emerson
Missoula, MT

Answer: Good and bad about Detroits: I would only suggest that you use what is referred to as a "soft locker" They are the later style that have been around for like over 10 years. The older ones were pretty harsh in operation and it was very important that the tire outer diameter was darn close. Remember, a Detroit is always locked and only unlocks when one wheel goes slower than the other, such as in a corner.

To properly explain how the Detroit Lockers work would take several pages. My new `87 Cherokee got a Ford 9-inch and Detroit right after I bought it. The rear end then went into my `90 Cherokee when I sold the `87. These were not "soft lockers." They clunked and jerked all the time, and put both my wife and I into circles a couple of times on slick roads. You had to learn not to back off when in a corner.

When I built the Scout project, "Tonto", I put in the then-brand-new soft locker in the rear and a Truetrac up front. What a difference. Never knew it was there. Well, okay, traction-wise one did, but not a problem on the street. You just still have to make sure tire diameter is pretty close. Had an old-style Detroit in my white CJ-5, both front and rear. Difficult to drive at speed in four-wheel drive, as it would pull to one side or the other. Took the front one out and put in a Truetrac. Hated it, mainly because sometimes it would not lock when needed, and you had to apply a bit of brake pressure. Hard to get the left foot over to the brake pedal on a CJ due to the way the steering column comes out. Liked the soft locker in the rear of the Scout so much, I pulled the Truetrac out, put in the soft locker up front, and kept the old style in the back. End of steering problems.

I don't think that you will have any problems with a soft locker in the rear of your Toyota. You just don't go into a big sweeping turn at speed and then back off really quick when there is ice on the road, or accelerate really hard and then back off really quick on ice. Oh wait, Toyotas don't accelerate very fast anyway! So, no problem.

I have soft lockers in both the front and rear of my military flatfender Jeep. Once in a while, in a very tight turn on a trail, the rear wants to push the front instead of letting it steer. In my case with my Atlas transfer case, I just disconnect the rear axle and let the front pull it around. However, I have only had to do that a few times and those were really bad trails.

One bad thing about the soft locker. If you should break an axleshaft under a hard load--you know, the type of load that makes the axleshaft make a "banging" sound when it snaps--there is a good chance that the rapid unloading will break a part inside the locker. No, it doesn't generally destroy the locker, just the internal part that can be replaced. Generally, you have to be doing something pretty stupid, or be really hardcore to break an axleshaft. (Ok, Dana 35s in Jeeps are an exception.)

Connect With Us

Newsletter Sign Up

Subscribe to the Magazine

Browse Articles By Vehicle

See Results