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Thread: Here's a real good tech read that I found on a local 4x4 forum

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    ** (Ryan) ** Senior member mudpupxxx's Avatar
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    Mt. Pleasant, MI

    Here's a real good tech read that I found on a local 4x4 forum

  2. #2
    I WARNed you about this Senior member budweiser_man's Avatar
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    Jul 2012
    Clackamas Oregon
    would have to register. copy and paste?
    74 Blazer, 350TBI/465/205, D60, 14BFF Detroit locker, DIY4x B52 hangers with 52inch springs, cross over steer, high steer, 4.10, DIY4x rear disk brakes, 37 boggers, WARN 8274, WARN Hubs, factory roll bars front and rear.
    Detroit built it, Detroit locks it.
    6 motors, 3 transmissions, 2 transfer cases, 4 sets of axles,

    If it aint broke, you aint trying.

  3. #3
    ** (Ryan) ** Senior member mudpupxxx's Avatar
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    Ok give me a while, it has lots of pics and I can't copy and paste them.

  4. #4
    ** (Ryan) ** Senior member mudpupxxx's Avatar
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    Mt. Pleasant, MI
    The 1 ton 14 bolt:........In mid 1972 GM replaced its dana 60/ Eaton rear 3/4 ton axles with a new design. The American Axle manufactured 14 bolt. This axle gets its name........because it has 14 bolts that hold the ring gear on...........and more also has 14 bolts that hold the diff cover on. The 14 bolt was standard for all 73-80 3/4 ton GM trucks.......2wd or 4wd. Its 10 1/2 ring gear and massive housing and brake drums made it damn near bomb proof. It was offered with a Gov Loc posi.......detroit locker...........and many ratios were available.........3.73.....4.10.....4.56. The axle shaft spline is 30 spline, and this axle is rated at hauling over 10,000 lbs. AFTER 36 years.................GM still offers this axle in its trucks................a credit of how durable the axle is.

    1974: Np203 offered in all GM 4x4 models stick or automatic ordered with V8. Locking diff was offered with Np203 full time 4x4. Front axles: were dana 44 1/2 ton. HD dana 44 3/ ton. Rear axles: 12 bolt 1/2 ton. 14 bolt 3/4 ton. trannys, 350 turbo, 3spd manual, SM465. T-cases.....Np203....Np205.........and dana 20. (74 was last year dana 20 was offered)

    1975: Sm465/203 combo was done away with. Last year Np205 could be ordered with auto trans. Also last year for full convertible K5 Blazers. Axles & trannys same as 1974.

    1976: In mid 1975 (76 model year) GM began to offer Np203 Full time 4x4 only with automatic tranmissions. And the NP205 was only offered behind manual transmissions. This would continue until mid 1979. k5 blazers came with a half metal cab and removable fiberglass rear roof.

    This is my 1976 Scottsdale K20, it originally came with a 400 small block (swapped out for 350) 350 turbo trans, Np203 full time 4x4, HD 44 front axle, 14 bolt 1 ton rear axle. With 4;10 gears. I swapped out the full time 4x4 drive flanges and installed the factory External bolt on Spicer hubs.

    Np203 shift lever in my 76 3/4 ton. The lever control and knob/range plate are correct for 73-78 203 equipted 4x4s. The rubber boot shown is NOT correct, it is for a 1979 203 equipted 4x4s. (I'll explain this later on) Fast Fact:....did you know that 73,74,75 Np203 levers are marked HURST......on the side of them........and were infact made by the HURST shifter company for GM.

    1977: This was the last year GM offered the HD dana 44 front axle........and it was only offered in early model 77 3/4 tons. GM did away with the large external hub rotor assembly and switched to the smaller 1/2 ton hub assembly for its 3/4 ton front axles. GM also started to use the saginaw style front driveshaft and switched to the FLAT style front flange on its T-cases.

    1977: k30 1 ton. The 77 model year marked the beginning of GM's 1st true 1 ton 4x4. This came standard with dana 60 front axle, choice of 400 turbo trans, with Np203 full time 4x4............or SM465 4spd with part time 4x4 Np205. 14 bolt rear axle. Engines ranged from 292 straight 6 to 350, 400, 454 V-8's. Axles for 1/2 ton's were the same as 73-77..................Axles for 3/4 tons were same (except for smaller Hub front dana 44). NOTE:...........the 1 ton dually models could be ordered with dana 70 rear axle......instead of a dually 14 bolt..........I've seen this in 81-87 1 ton duallys 2wd/4wd..........not 100% sure if they offered it for 73-80..........but I'm guessing they did.

    1978: Drivetrain same as 77 for 1/2 ton 3/4 ton..........and 1 ton. It was around 1978 that GM began to offer its own front axle.........which replaced the standard Dana 44 that GM had used for more than 10 years. This was the Corporate 10 bolt front axle, which would be in use until 87 for trucks and 91 for K5 blazers & suburbans.

    1979:........The 79 model year was the last year for Np203 full time 4wd. Axles for 1/2 tons were 10 bolt front......12 bolt rear..........3/4 tons........10 bolt front.........14 bolt rear. 1 tons........dana 60 front.....14 bolt rear (single rear wheel K30's).

    Also GM installed a dash light for full time Np203's.........lever in LOC position........the light comes on in instrument cluster. ( this might have been used in earlier years.....78,77...back for Np203 full time) but I havent been able to find out. It was not offered for 73-76 Np205 equipted 4x4's. I know it was at least offered in 79 as my 79 GMC 1/2 ton has it. And I'm guessing it was also used in 79 NP205/sm465 equipted vehicles as well. The dash light was standard from 1980-91 for either T-case used at time (Np205,208, or 241)

    This is my 1979 GMC 1/2 ton. It has the original 350 motor. 350 turbo trans & full time Np203. Axles are 10 bolt front, 12 bolt rear, with 3.73 gearing.

    In 1979, GM redesigned their Np203 lever assembly, they did away with the metal range plate (Hi... Hi Loc.. ect..) and put the shift pattern on the control knob (this knob will not fit 78-back 203 levers....The lever thread is different) GM also used a new rubber shift boot with metal ring molded into it...........and it used a large metal retainer plate that was bolted over top of it. ( 1979-91 Np205 equipted trucks use the same rubber shift boot/ retainer ring) (79 Np205's also had shift pattern engraved on their shift knobs).

    Shown is my 79 gmc's shift lever.

    1979: The 305 (5.0) motor was in use by now.

    1980: This was the only year GM offered only 1 transfer case in its 4x4 line up. ALL 1980 model GM 4x4s came with the NP205. By 1980 the 205 had a slip yoke rear (it had been used since 78/79). 1980 also marked the last year for the 73-80 body style. 1980 was also the 1st year GM offered sqaure headlights on its trucks , they were optional, but were standard on Silverado package.

    Shown here is a Slip yoke Np205 from a 1980 chevy that was bolted to a 350 turbo. Also shown are the shift rods & bar.......there is no adjustment on Np205 linkage.

    1980: axles for 1/2 tons 3/4 tons, & 1 tons remained the same as 79 model year. trannys, 350 turbo, 400 turbo, 3spd on column, or Sm465. T-case........Np205 for all 80 models. NOTE:..........The 400 small block offered in GM trucks was being discontinued around this time (either 80 or 81) it had been offered since 74/75.

    1981: GM redesigned the front clip & interior on its trucks, sqaure headlights standard, other than grille changes (81-82) (83-84) 85-87) body metal didnt change for trucks until mid 87 (for 88 model year).

    1981: The NP208 made its way into all 1/2 ton's & 3/4 tons. ( 1 ton K30's still used the Np205) The Np208 was supposedly were things all went wrong...........the case was a 2 piece alumnium housing.........chain was seen as much weaker than its older brothers (Np203....Np205). The Np208 did come with an excellent Low range ratio of 2.61.............and while for many years off roaders shunned this transfer is highly desired by those seeking a good low range T-case to replace their Np205 or Np203. One of the reasons GM switched to an aluminum T-case was for (weight savings). Jeep had been using an all aluminum full time (quadra track) transfer case since 73/74. Both Ford & Dodge began using the Np208 in 1980.
    The Np208 was able to ( shift on the fly) at up to speeds of 25mph, the range box featured a light.......that when your headlights/instument cluster lights were on.......lit up at night.......a nice feature to have.........and one that GM continued to offer in its 88-2000 CK 4x4's.

    Shown is a 81-87 Np208 and both its driveshafts (notice the front is standard Saginaw style driveshaft)

    The Linkage side of an Np208...........Linkage adjustment can be done on 208's.

    Np208 transfer case ID tag, this tag will tell you the Year the T-case was made, and its Low Range ratio. This type of ID tag is standard on Np208's and Np241's. NOTE:.........69-79 Np205's....and 73-79 Np203's use a BLUE metal ID tag affixed to the front of the T-case below/behind the Shift linkage..........these can rot off/corrode over the years, but thats where they are located at.

    The Np208 lever assembly..........the range position lit up at night with vehicles lights on. This particular 208 lever is out of an 85-87 truck. You can tell by the type of 4x4 knob used. Gm used it from 85-94.

    NOTE: Early model GM Np208s (i'm guessing 81/82) came with Nylon shift forks (inside T-case) These plastic shift forks had a tendency to break..... these were later replaced with aluminum shift forks.

    1981: GM redesigned the Sm465's rear was much longer than previous (68-80) models. GM's reasoning for doing this was that by lengthening its 465 rear shaft, it did away with the coupler (inside T-case adaptor) that was nessesary in previous years(68-80) The 81-87 SM465 was offered in 32 spline only. This benefited GM in that it could bolt a 32 spline NP208 or 32 spline Np205 up to the Sm465 or the 400 turbo.

    SHown here is a 81-87 Sm465, this particular one came out of an 83, notice the long tailshaft........and also notice the chrome shift rod which became standard for 81-87 Sm465's. Sombody installed a 68-74 Sm465 pattern shift knob on this.

    1981: This was the last year GM used the 350 turbo tranny, the 81 4x4 350 turbo tranny is very that it was the only year GM offerred it hooked to the Np208. The rear tail shaft on it is much longer than previous 4x4 350's (1970-80).

    The 1970-1980 4x4 350 turbos came with short rear tailshafts, and were made to work with the Np205, and 73-up Np203, and while the 205 used an adaptor with coupler inside it to spline into the trans/T-case. The 203 used a very thin adaptor plate, and no coupler at all. In 81 GM lengthened its 350 turbo rear shaft and in doing so, this did away with either a thin adaptor plate, or adapter housing coupler. You cannot bolt a 208 up to a short tail shaft 350 without modification's.

    Shown here is a 4x4 350 turbo with adaptor out of an 81 chevy, notice the longer rear shaft. Also this trans is a K-case model, and it has a locking torque converter.

    1981: NP205's were used only in 1 ton K30 models....and this continued till 91 in old body style 1 ton 4x4's.

    1982: The new for 82..... 700R4 4spd automatic made its debute in 82. This trans had problems for several years after it came out, until GM revampted it. Even then, it still got such a bad rap, that guys would jerk them out, and install 350's or 400's for more reliabuility. The 700R4 was GM's replacement for the 350 turbo. The 700 was standard in 1/2 tons.......and even optional in 3/4 ton's. It was NOT offered in a 1 ton k30.

    1982: AUTO LOCKING HUBS. This was also a NEW for 82 thing. GM's auto locking hubs were a big seller from 82-91, they were reliable under normal use. But the hubs had drawbacks. SEE Locking hub Page.

    1982: 82 was the last year for the 12 bolt rear axle, its replacment was the less than strong 10 bolt rear axle...............which is still used to this date!!!!........the axle housing has slightly changed over the years.

    1982:....While GM was still using the Sm465 and 3spd on the tree......................they did offer an ODD BALL manual trans that was a 3spd with OD (NEW PROCESS A833)......and this was used in 4x4's..............some even with diesel engines.
    The trans had an aluminum housing & was floor shifted .........and really was not meant to be in a 4x4....but it did not have low 1st gear..........this tranny was forerunner of the 88-up Getrag 5spd.

    1982: GM began to offer a SEMI FLOAT 14 bolt rear axle in its 3/4 tons................this axle became standard in a 3/4 ton model 2wd or 4wd. The 1 ton 14 bolt could be ordered in a 3/4 ton, but very few ever were.

    Semi Float 14 bolt: This axle while less strong than its 1 ton full floater brother, is none the less strong.........compared to a 10 bolt or 12 bolt. The housing is large, the axle shafts are heavy duty, the main drawback is its ( C Clip) design, which both the 12 & 10 bolt axles shared as well.

    1982: ( 1/2 ton's came with...700R4,sm465, 3spd on column, Np208, 10 bolt front, 12 bolt rear)(3/4 tons 400 turbo, (700R4 optional) Sm465, Np208 10 bolt front, semi float 14 bolt rear). 3spd OD manual trans optional also. ( 1 ton K30.....400 turbo, SM465, NP205) dana 60 front, full float 14 bolt rear)

    1983: 10 bolt rear axle standard in 1/2 ton's. (GM's S-10 Blazer & truck came out in 83....they replaced the Chevy Luv...pickup)

    1983-87 Tranmissions & T-cases used are same as 1982.

    My 1986 Scottsdale K20, this has its original drivetrain as well, consisting of a 350 motor, 700r4,Np208, 10bolt front, 14 bolt SF rear both with 3.73 gearing. With the introduction of the 700R4 in 1982, GM began offering this trans in its 3/4 ton pickups, both 2wd and 4wd.

    Interior of the scottsdale package offered in my 1986 K20, (seat cover was not factory installed)

    rear 14 bolt (SEMI FLOAT) in my 1986 K20, this axle was standard in most 82-87 3/4 ton 2wd and 4wd GM trucks & suburbans, the heavier 1 ton 14 bolt was available as an order option, for heavy towing, and or those who ordered the 454 motor motor. Very few 82-87 3/4 ton's were ever ordered with either option though.

    Factory Front Tow Hooks: were optional through the years, but many trucks were not ordered with them. By the mid 1980's they were becoming more popular. These are factory GM tow hooks that were offered for 81-87 GM trucks.....and 88-91 suburbans and K5 blazers. NOTE: these tow hooks will not bolt on to earlier 73-80 GM 4x4's without modifications, the front frame rail horns are different.

    1981-87 Transfer case Control Sticker on sunvisor for Np208 in my 86 K20. This sticker was used on all 81-87 gm 4x4s (except K30 models) and also 1988 model suburbans. It would have been used on 89-91 K5 blazers and suburbans as well, even though they had switched to the Np241 for both of these in 89.

    1987: EFI (Electronic fuel injection) offered 1st time in GM was standard. It replaced the carburetor. 1987 was the last year for this bodystyle truck. The k5 blazer and suburban........were still made in this body style till 1991. The 1ton K30 would still be made till crewcab & cab chassis models.

    1988: The new IFS (independent front suspension) CK chevy/gmc trucks came out. This new design was revolutionary in terms of technical advanment, yet to many hard core chevy fans.........this new body style 4x4 truck looked an drove more like a car..........than a truck!! The IFS proved to be inferior to the older solid front axle.................which FORD AND DODGE were still using...............and Still do use to this day!!.

    1988: trannys were same, 700r4.....400 turbo, SM465. ( 3spd on tree was discontinued in 86) Getrag 5spd offered for 1st time. T-case's were Np208 for suburban & K5 Blazer. IFS trucks used the Np241. Axles were IFS for CK 1/2 ton,3/4ton & 1 ton. Old body style K30......used solid front dana 60 axle & Np205 T-case.

    1988: Np241 transfer case. This T-case is nearly identicle to the Np208.........its chain driven and aluminum housing share similarities. Yet the Np241 has a slightly lower low range of 2.72...........compared to the 208's.....2.62 low range.

    1988: GETRAG 5spd. This trans was 1st offered in the new 88 C/K body style trucks, it was offered in 1/2 tons and 3/4 tons. The Getrag had no granny gear, its housing was all aluminum (supposedly 1 piece aluminum). The Getrag is good for normal use, but for serious off road abuse, it will not hold up for long. Up against the Sm465....the getrag is much weaker. GM used the getrag well into the 90s....and possibly early 2000's.

    1988: 6 lug Semi Float 14 bolt:.........GM began to offer this axle in its 1/2 ton trucks.............and even light duty 3/4 ton trucks (both of which were 6 bolt pattern). The axle housing is the same as the earlier semi float 14 bolt.........and the only difference is in the wheel pattern of its axle shafts. (6 lug & 8 lug) This axle was used well into the mid/late 90's. My 1995 1/2 ton ext. cab 4x4 has this same axle.

    1989: Np241 T-case became standard in K5 Blazers, and suburbans till 1991. (The Np241 was used in new body style K5 blazer & suburban in 1992)

    1990:...same as 1988.

    1991: Last year for old body style K5 Blazer and Suburban, last year GM offered a solid front axle 4x4. Last year for NP205 used in old K30 body style 1 tons.

    The SM465 was still being used...............but it would soon be replaced by the NV4500 5spd manual trans, which offered a low 1st well as a OD.........and this trans had a cast Iron housing, and proved to be quite strong. Unlike the Sm465, which was offered in all truck models..............the NV4500 would only be offered in heavy 3/4 ton's with a GVW rating of 7500lbs or higher.

  5. #5
    Knows their $hit AL P's Avatar
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    Jul 2012

    I`m saving this!
    My 87 blazer..(RC 4in lift kit on the way..33 X 12.50 X 15 wrangler duratrac tires..just a tad worn..LOL)..My blazer runs pretty good, but I have found that it is infact NOT faster then a speeding bullet!!

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