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C. Jeep T18

Borg-Warner T18 Transmission

The T18 transmission was designed as a replacement for the already successful T98. The transmission was used by numerous automobile manufacturers including Ford, International Harvester, and Jeep.Although the T98 was Jeeps first granny low transmission, it was the Jeep T18 that reached the American masses.The T18 introduced the idyllic attributes that jeep would be synonymous with: strength, low gearing, and dependability.

Jeep incorporated the T18 into their product line in 1966. The T18 transmission offered some benefits over the T98.Both were excellent transmissions; however, the T98 was more susceptible to wear since the bearings and lubrication system were not as efficient. The T18 also provided twice the bearing support on the cluster shaft than that of the T98.

The cast iron T18 transmission case measures 11.87" in length, 17.45” in height, and weighs approximately 145lbs. The T18 utilizes a cast iron top cover which is retained by six bolts. The early T18 transmissions had a top cover with “T98” stamped on it, which often causes misidentification. The case may also have a casting # of “T18” or “1301”.The Jeep T18 case has a front pattern that is 8.50" across the top, 2.75" from the top to bottom hole on the driver's side and 4.62" top to bottom on the passenger side of the transmission. Jeep CJ 1977-79 used the Ford butterfly pattern and the input shaft is 7” as the pilot bushing is further inside the crankshaft, with our special pilot bearing AA716156 a Ford shaft can be used, the diameter is the same.

The PTO port is located on the driver's side of the transmission for both Ford and Jeep.

Ford T18's have a front bolt pattern of 8.5” wide x 6.3125” tall, known as a butterfly pattern and is compatible with AMC/Jeep bellhousings that utilized the T150/T176 transmissions as well as T18 Jeep transmissions 77-79 CJ as well as 77 and later full size Jeeps. All Ford T18's are 6.32 to 1 in granny 1st gear. The input gear stick out length is 6.50”.

The rear of the Jeep T18 was typically a 1-3/8" x 6 spline output shaft for mounting to the input gear of the Dana 18/20 transfer case. The transmission was connected to the Dana 18/20 via a 1” thick cast iron adapter plate held in place by 6 bolts.

The Ford T18 will require AA adapter 50-7201 to connect to a model 18 or 20 Dana/Spicer transfer case, the Ford case has a 4 bolt pattern, this kit comes with the special pilot bushing AA716156 as well as all pieces required to bolt the T18 to a model 18/20. We offer other adapter kits for all the different transfer cases.

There was also an odd T18 combination used in Jeep trucks.T18 was used in 1980-1982 J-20 pickups where the transmission was mated to a round circular six bolt patterned NP208 transfer case. This version of the T18 utilized a longer 8” tail housing with a 23 spline transmission output shaft.

The T18 was offered with two different shift patterns.The earlier T18s have a reverse up and next to third. Transmissions manufactured after 1978 have reverse down and next to forth gear.The reverse shifter fork was relocated from the drivers' side of the case and into the top cover.The location of the reverse gear lever influences the shape of the transmission case.Earlier transmissions have a significant bulge on the driver side of the case. The later t18 transmissions have a flatter surface on the driver side of the case.

The Jeep T18 was offered with two distinct gear ratio options.These are commonly referred to as the “close ratio” and the “wide ratio”. The Granny low ‘‘close ratio” was offered with a 4.02:1 first gear ratio and had overall good gear spread.The “close ratio” T18 transmissions offer a more road friendly drivability. The “wide ratio” T18 transmissions offered an impressively low first gear of 6.32:1.This alone makes this transmission desirable and heavily sought after by serious off road enthusiasts.The complete gearing is as follows:

Transmission

1st

2nd

3rd

4th

Rev

T-18

4.02

2.41

1.41

1.00

4.73

T-18A

6.32

3.09

1.69

1.00

7.44

The gear ratio differences can result in some confusion. The complexity becomes compounded by the variety of transmission input shafts. Jeep used over a dozen different input shaft variations on the T18. When sourcing a transmission from a donor vehicle, the variations in input shafts can cause confusion and frustration. It is very common to see individuals purchase T18 transmissions under the promise of finding a good deal only to find their T18 is unusable for their application.

We have also put together a more detailed technical section on the T18 and T98 conversions. Please review this section for a better explanation on the differences, commonalities, and adaption options for these often misidentified and misunderstood transmissions.

O.A.L Tooth Jeep Warner

Year of Input Shaft Count Number Number

1980-81 (T18) 15-7/8"- 8 Cyl. S27-L17T 8132656 T18-16P

1977-79 (T18) 10"-6 Cyl. S27-L17T 8130260 T18-16J

1979 (T18) 15-3/4"- 8 Cyl. S27-L17T 8130258 T18-16G

1975-78 (T18) 16"- 8 Cyl. S27-L17T 8125946 T18-16K

1967-78 (T18) 12"- 6 Cyl. S27-L17T 941110 T18-16F

1976-79 (T18C) 10"- 6 Cyl. S27-L23T 8126875 T18C-16N

1972-75 (T18C) 12"- 6 Cyl. S27-L23T 8121360 T18C-16B

1973-74 (T18C) 16-3/4"- 8 Cyl. S27-L17T 8123036 T18C-16D

1971-73 (T18C) 12"- 258 6 Cyl. S27-L23T 8122416 T18C-16B

1971-72 (T18C) 16-3/4"- 8 Cyl. S27-L23T 998602 T18C-16C

1968-72 (T18) 15-3/4"- 8 Cyl. S27-L17T 991394 T18-16K

1965-72 (T18C) 14"- 8 Cyl. S27-L17T 940505 T18-16D

In order to assist you in determining the necessary adapter plates for both the T98 and T18 transmissions, we have listed the adapters that correspond to the transmission stickout length. The stickout length is usually 2-5/8" less than the O.A.L.

O.A.L. GM Kit Ford Kit

Stickout Of Input Shaft Number Number

7-3/8" 10" 712549 CHEVY 1977-79

7-3/4" 10-3/8" 712512 CHEVY 712514 FORD

9-3/8" 12" 712521 CHEVY 712522 FORD

10-1/4" 12-7/8" 712517 CHEVY 712518 FORD

11-3/8" 14" N/A

13-1/8" 15-3/4" 712516 CHEVY

13-1/4" 15-7/8" 712516 CHEVY

13-3/8" 16" 712516 CHEVY

14-1/8" 16-3/4" 712516 CHEVY

On any transmission that has a 17 tooth input shaft, you have the option of installing a new shorter input shaft. If you are using a T98 or T18 in a short wheel base vehicle, drivetrain length is crucial. These input shafts have a 17 tooth gear and allows us to use a 1/2" thick adapter plate. PN712512 for a T18 and PN712512-T98 for the T98 transmission is to a Chevy engine. PN712514 for a T18 and PN712514-T98 for the T98 transmission is to a Ford engine. These adapters are 1/2" thick adapter plates (thin design) that come complete with a new input shaft for your transmission.

The other adapters listed are for when you are retaining the stock input shaft. The transmissions with a tooth count of S17-L23T must retain the stock input shaft, since there are no short-style 23 tooth gear input shafts. The longer transmission input shafts are normally retained on long wheel based vehicles. If you attempt to use the short style adapter on a long wheel based vehicle, you will have trouble with the shifter & linkage.

For vehicles that have the longer input shaft (O.A.L. of 15-3/4", 15-7/8", 16", and 16-3/4"), we offer PN712516. This kit requires you to modify the existing aluminum spacer between your transmission and Jeep bellhousing. It will eliminate the need to change the stock input shaft and will possibly eliminate the need for driveshaft modifications.