What is the largest size of tire I can put on my S10/S15?
The largest tire that will fit on a stock S series is a 30" tire. The torsion bars may have to be adjusted a little bit and not all brands will fit. This is due to some size variation in specific tire sizes between manufacturers. A lift kit should give you about a 1" increase in tire diameter for every two inchs of lift. The maximum size with lift kits installed is around 33".
Refer to the TIRE/LIFT info Page

What kind of automatic transmission do I have?
GM used five different automatics in their trucks. The transmissions available were the Hydromatic 180c, 220c, THM 700-R4, 4L60, and 4L60-E. The 180c and 220c are three speed transmissions and were used on the early model S vehicles. The 700-R4 & 4L60(-E) are four speed automatics and are used on the late model S vehicles.

What Transfer-Case do I have?
All early model S Series vehicles with the 2.8 V6 use the NP 207 while most late model vehicles with the 4.3 V6 use the NP 231. S Trucks equipped with the MFI Turbo Engine use the Borg Warner 4472 t-case. 1991 - 1993 models equipped with the electronic shift t-case use the NP 233.

Descriptions:

The Model 207 transfer case is an aluminum case, chain drive, 4 position unit providing 4wd High and Low ranges, a 2wd High range and a Neutral Position. The 207 is a Part-time 4wd unit. Range Positions are selected by a floor mounted shift lever.

The Model 231 is a part-time transfer case with a built in, low range, gear reduction system. A front axle disconnect is used for 2-wheel drive operation. The 231 has three operating ranges - 2-wheel drive High and 4-wheel drive High and Low, plus Neutral. The 4-wheel drive operating ranges are undifferentiated.

The Model 233 is an electronic shift transfer case that has three modes of operation: 2wd range, 4wd high, and 4wd Low. Gear reduction for low range is provided by a planetary gear set. The floor-mounted shifter has been replaced by a dash-mounted switch for these units.

The Borg Warner 4472 transfer case is a 2-piece aluminum case, chain driven, viscous clutch type transfer case. This produces a system in which all wheel drive is engaged all of the time. Torque is transmitted through a planetary gear set which distributes torque at a ratio of 1/3 front and 2/3 rear.

What kind of Lube should I use in my transfer case?
NP207 - Dexron II automatic transmission fluid (or equivalent), 80w or 80w-90 GL5 (refer to the owners manual to be certain) NP231 - Dexron II automatic transmission fluid (or equivalent)

What size motor do I have (current to '93)?
The S Series vehicles have been equipped with three I4 engines and two V6s. The I4 engines are available in 1.9, 2.0, and 2.5 litres. The 1.9 litre was offered during 1982 through 1985. The 2.0 litre was available from 1983 to 1984. The 2.5 litre was available from 1985 to 1993. The 2.8 litre V6 was available from 1982 to 1993. The 4.3 litre was available 1988 onwards. there also was a 2.2 litre diesel available from 1983 to 1985. The 1.9, 2.0, and 2.8 litre engine were equipped with carburation until 1986. The 2.5 litre was only available in Fuel Injection. All engines available from 1986 onwards have Throttle Body fuel injection. In 1991 and '92 the 4.3 came with an MFI-Turbo option on some trucks. Also in 1992 and '93 some 4.3 litre engines were equipped with a Central Multi-Port Fuel Injection System (CMFI).

I want to increase the power of my 2.8 V6. What can I do?
Besides the usual goodies (K&N filter, headers, cat back exhaust, chip, etc.) GM Goodwrench makes a 3.4 V6 crate motor to replace the 2.8 V6 in all '82 to '85 S trucks. The 3.4 V6 is said to be a virtual drop in with all the components from the 2.8 V6 as well as the old transmission fitting in. Another option is to get an old 3.4 V6 out of a '95 or earlier Camaro and swap that in. Others have swapped in a 3.1L out of a different GM vehicle. It's the same block but stroked.

chevy@off-road.com.

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