2B. 4WD transmission options and conversion part numbers

Transmission Options:


When installing a TH350 into your 4WD S10/S15, there are several parts that you will need. The transmission will need to be equipped with an adapter kit. Our kit is furnished with a modified output shaft and a spacer plate that is 1-1/2" thick. You will be required to remove the ears on the transmission as illustrated in the GM Automatic Transmission section of this manual. This added clearance will allow for frame and exhaust clearance. When replacing a 700R transmission, you will need to install a new shift indicator and rework your existing shift linkage. The overall length of the TH350, adapter housing, and GM adapter will be equal in length to your original transmission so that driveshaft modifications will not be required. You will need to purchase two additional parts from your GM dealer, if you are replacing a 4 or 5 speed transmission.

AA PN50-8500 - TH350 to S10/S15 NP207 transfer case adapter kit TH350 4WD dwg

P/N 15681328 - *GM Adapter Plate

P/N 14049551 - *GM Shifter Bracket

P/N 25053892 - GM Shift Indicator

P/N 3973000 - GM Kickdown Cable Bracket

Items with "*" are only required when replacing a manual transmission.

The special output shaft supplied with our transfer case kit is a stock TH350 output shaft that has been modified in the splined area. We have provided a spline relief that will permit the new shaft to engage into the transfer case female splines. Any attempt to use the original TH350 shaft that has not been modified could result in pre-loading the input bearing and output shaft of the 4WD assembly.


If your vehicle was originally equipped with a 700R (60 degree) transmission, you will need to change the transmission to a 700R or 4L60E from a full-size GM vehicle. In the full-size Chevy trucks and Blazers, these transmissions were used with a V8 engine. The smaller S10/S15 700R transmission has an identical main shaft and rear bolt pattern as the full size 4WD transmissions. You will have to retain the stock S10 transfer case adapter. On the 4L60E transmission, you will require a reluctor ring and sensor to operate this transmission properly. 700R dwg

If you wish to retain your stock 700R-4 transmission and couple it up to in your new V8, you can simply have your internal parts exchanged into the larger case (V8 700R or 90 degree bolt pattern 700R).

Check with your local transmission shop for the lockup converter requirements of your 700R-4. Driveshaft modifications will not be required when reusing the new V8 case.


We offer a kit for the installation of the TH400 into your S10/S15 using your stock transfer case. This kit will require driveshaft modifications and the installation of a new output shaft into the TH400 transmission. You will also be required to install a new shift indicator and rework your existing shift linkage if you are replacing an automatic transmission.

If you are replacing a manual transmission, then you will need to install a new floor shifter. The assembled length of the TH400 adapter will be slightly longer than the original transmission assembly. Listed below are the parts necessary for your installation.

AA PN50-8501 - TH400 to S10/S15 NP207 transfer case adapter kit TH400 4WD dwg

P/N 15681328 - *GM Adapter Plate

P/N 14049551 - *GM Shifter Bracket

P/N 25053892 - GM Shift Indicator

P/N 3973000 - GM Kickdown Cable Bracket

Items with "*" are only required when replacing a manual transmission.

The Borg Warner T4 & T5 transmissions have been available in the S10 since their inception. These transmissions are somewhat reliable for engines that produce less than 225 ft./lbs. torque. They offer ease of shifting and overdrive capabilities. Most people prefer to replace these transmissions with an automatic. However, we have found that when using them behind a V6 or V8, they will withstand the increase in torque and horsepower. These transmissions utilize a standard corporate GM bolt pattern on the face of the transmission. The input shaft of the transmission has a special spline size of 1"-14.

When using this transmission in conjunction with the V6 or V8 engine, you will need to make a couple of modifications to the transmission. The first modification is to remove the bearing retainer and shorten it 1". This prevents the retainer from bottoming out into the pressure plate. You may also need to shorten the tip of the input shaft slightly to avoid it bottoming out into the crank. The clutch disc, P/N 716102, will provide the proper engagement of the clutch disc hub with the input shaft on the transmission. The T5 used with the late model Camaros, also use the same 1"-14 clutch disc size. If you attempt to use the Camaro disc, you should be careful and inspect the disc and input shaft spline for proper clearance. It may be necessary to modify the length of the clutch hub in order for it to be compatible with the T5 transmission. DO NOT USE the Astro Van 11" disc.

The new bellhousing will have a bolt pattern that will be identical to the T4 and T5 transmissions. The manual transmission conversion SHOULD NOT be used on 1983 4WD vehicles. These vehicles were equipped with a cable-operated clutch system that is very expensive to convert to the newer hydraulic system. Therefore, if you have a 1982-83 vehicle, you will need to convert to an automatic transmission. If your vehicle is a 1984 or newer, the modifications to your transmission and parts will facilitate a trouble-free installation.

In order for you to bolt your original manual transmission to the Chevy engine, you will need to purchase a new bellhousing assembly, P/N 712547. This bellhousing uses a internal hydraulic slave cylinder. The indexing diameter of the new bellhousing is 4.686".

PN712547 - GM bellhousing assembly kit inside bellhsg hoses thru boot 2-8 GM T5 bshg

PN716102-P - 11" Pressure Plate

PN716102 - 11" Clutch Disc


The parts listed on this section are compatible with all 4WD S10/S15 V8 & 4.3 V6 conversions. Refer to the General Conversion Information Section of this manual for additional conversion considerations.


We manufacture bolt-in motor mounts for the early S10/S15 4WDs. They work in conjunction with the stock 2.8L frame mounts. If your vehicle was equipped with a 4 cylinder, it is necessary that you purchase and install a set of stock 2.8L V6 frame mounts, GM Part No. 22188284. On 1990 & newer 4 cylinder applications, you will need to purchase a set of 4.3L mounts (both frame & rubber mounts): P/N 713123

PN713107 - Chevy V8 to 2.8L stock frame mounts

PN713123 - Chevy V8 to stock 4.3 V6 motor mounts

These motor mounts listed above are slotted for fine-tune adjustments. On vehicles retaining the air conditioning, the engine must be set to the furthest rear position available on the motor mount. When this is done, clearance on the A.C. evaporator housing becomes crucial on the passenger side exhaust manifold. We manufacture a sheet metal cover that will allow ample clearance between the manifold and housing. (P/N 716421)


When converting to a Chevy V8, 4WD applications require a special rear sump oil pan. Our oil pan comes complete with a new pickup tube and screen to help with the installation. Do not attempt to reuse your original V6 pickup tube. Once the new oil pan has been installed, you will be required to modify the dipstick by re-calibrating the volume of the new oil pan. These modifications should be made with 5 quarts of oil in the black powder-coated pan, and 6 quarts of oil in the gold-colored pan. These volume measurements will allow for the 1 quart volume required for the filter.

The oil dipstick will be need to be re-calibrated to read properly. Once the oil has been added to the new pan, you'll need to start the engine to circulate the oil. Once the oil has been circulated, insert the dipstick into the pan. Most dipsticks will require shortening in order to fit into the pan. Once the dipstick is fully inserted, remove it and locate the oil level. This is the ideal oil level for your new pan and it should be marked on the dipstick as a reference level. We also recommend that you verify this depth after the engine had been filled to the proper oil level. Make sure that you measure the location of the pickup screen in conjunction with the new oil pan. The screen should be approximately 1/2” above the floor of the pan.

If the equipment is available, you can manufacture your own modified oil pan by removing the lower portion of the 2.8 V6 pan and welding it to the upper portion of the Chevy V8 pan. Be sure and test the oil pan for possible leaks prior to assembly. The oil pickup tube used on the V8 engine is the same as the oil pickup tube used on the 2.8 V6 engine.

On Chevy 4.3 V6 engine conversions replacing the 2.8 V6, you will need to use the stock GM oil pan used on S10 4WD vehicles. These vehicles were introduced in 1989. This new oil pan will not be compatible with 4.3 engines prior to 1986.

Depending on the year and style of the block, we manufacture three different oil pans for the Chevy V8s. All pans come with a new pickup screen and oil plug. The 1986 & newer pans will work on LT1 & LT4 engines, but the pickup screen will not fit the LT1 & LT4 oil pump and our pans do not offer oil level sensor provisions. These pans do not work on LS1 engines.

Modified Oil Pans: PN716410A - 1985 & earlier Chevy block, driver's side dipstick

PN716411A - 1985 & earlier Chevy block, passenger side dipstick

PN716420A - 1986 & up Chevy block, 1 piece rear main seal


When installing a V8 into the 4WD S10, you will be required to use a remote oil filter adapter. This is needed because the front driveshaft comes up on the driver's side of the vehicle and is in the same location as your oil filter. We have a remote oil filter adapter available, or you may purchase it from your local auto parts store. Our kits come complete with all of the necessary high-pressure hoses and fittings.

PN716083 - Chevy V8 oil filter adapter

PN716085 - Chevy 4.3 V6 oil filter adapter


We manufacture two types of exhaust headers. The 4WD "SlickFit" headers are furnished with the passenger side extending upward and the driver's side dropping downward. With the passenger side extending upward, you will be able to eliminate the modifications required for the front shock tower. If you are not using a body lift, you will need to make modifications to the A/C evaporator housing. Most 4WD vehicles that are equipped with body lifts will not require any modifications.

Our SlickFit headers will not work with Trans-Dapt or Hooker Header motor mounts. NOTE: Our headers are not designed to fit Chevy small blocks with angle port heads.

DO NOT USE any type of header wrapping material on the SlickFit header or you will void the warranty.

Our headers are manufactured with a 5/16” header flange and 16 gauge tubing. Both types of headers use a slip-type exhaust connection which aids in additional clearance when exiting from the engine compartment. These headers are available in Chrome or Non-plated (NP). (We do not offer headers for the 4.3 V6 application.)

PN717053 - SlickFit headers, Chevy V8 (manifold style)

P/N 717053 headers will provide excellent steering shaft clearance, and on the passenger side eliminate the need for shock tower relocation. However, the header design is not symmetrical from side-to-side. You will notice from the illustration that the passenger side header angles above the ports, while the header on the driver's side angles below the ports.


When using an automatic transmission, we recommend that you use a 168 tooth flexplate. In both applications, make sure that you do not obtain these parts from a Chevy small block 400 that was externally balanced. Obtaining the wrong parts will cause severe vibration in the drivetrain. Make sure that your flywheel is compatible with your engine selection.

In manual transmission conversions, you can use either the 153T or 168T flywheel. For more information, refer to the Transmission subheading in the General Information section of this manual.

PN716102-P 11" Pressure Plate

PN716102 11” Clutch Disc

We highly recommend the use of these cutch components. Failure to do so could result in improper clutch disengagement.


If you are using a manual transmission, you will need to use our bellhousing kit. This bellhousing is the only proven method of adapting your manual transmission to the new V6 or V8 engine. Our kit comes complete with a internal release bearing, pilot bushing, and hardware. The manual transmission conversions are NOT compatible with vehicles 1982-83 that are equipped with cable clutch controls. We highly recommend our 11” pressure plate with this bellhousing; and the 11”, 1”-14 spline clutch disc is required.

PN712547 - GM bellhousing kit

PN716102-P - 11” Pressure plate

PN716102 - 11” Clutch Disc


If you are converting to an automatic transmission, any GM stock torque converter will work with your TH350. If you are using a 700R, you will be required to purchase an aftermarket lockup converter kit. We offer a lockup bypass kit.

PN24-700R - 700R Lockup Bypass Kit


This crossmember is only found on 4WD S10 vehicles. This crossmember is directly beneath the transmission bellhousing area. This crossmember will need to be modified by removing a section that is 12" wide and 1" deep. This crossmember is an integral part of your S10 structure and must be retained. You will also notice that your brake line is attached to this crossmember. Crossmember drwg


When installing the V8 there will not be any driveshaft modifications required. The back of the V8 engine block will be in the same location as the original V6 or 4 cylinder engine block. The new transmission should have the same overall length as the transmission being replaced.


On 4WD models, you will find a vacuum shift controller that is used to engage the front axle assembly. Due to its awkward position, you will need to relocate it out of the way of the new V8 engine. This can be remounted underneath the battery tray area. Select a new routing for the cable, making sure you will have a smooth unobstructed movement. New holes may be necessary and a new vacuum line will need to be installed to the new location. Vacuum shift control


Our adapter kit for the TH350 comes with an output shaft and adapter housing to retain the stock transfer case in its original location. On vehicles that were previously equipped with a 5 speed, it is necessary to purchase the following GM items: GM# 14049551 (shifter bracket) and GM# 15681328 (stock adapter). stock GM plate Shifter assy 4wd TH350 adapt

PN50-8500 - TH350 to stock S10/S15 NP207 & NP231 T/C