Ben Neil took these photos, and says, "Here is the highly sought-after T98a 'granny gear' 6.34, with factory adapters that bolt it right into all CJ-2A, 3A and 3B flatfenders.
"This factory option T98a (top front view at left) was removed from a 1970 CJ-5 that had the 134 cu. in. F-head 4 cylinder. It was one of the last years Jeep offered a T98a, which began in the early 1960s. This one had a D20 transfer case with a single shift lever. Thetransfer case is 29 count spline, small hole.
"This last of the factory T98a's has a mixture of parts during the changeover to T18 transmissions. The shift tower is T18. If you have the option get one with the transmission support and driveshafts.
"Just as a footnote, this one was sold for $900.00, in my opinion a fair price. Aftermarket adapters are very expensive and longer than the 1-inch-thick cast iron factory pieces. Hope this will help the guys who are looking for one."
Bill Derkland grabbed some detail shots of the front of the transmission (90K JPEG) and a rear view (80K JPEG) to give a closer look at some of the details.
Eric Lawson has a T98a in an early CJ-5, and comments, "Somewhere I have a couple of adapters for the T-98 to 4F-134. One is cast iron and the other is aluminum. There is, I believe, another adapter that goes between the transfer case and the transmission.
"The advantage to this transmission is the 1st gear. Overall gearing of the T-98 in 1st gear, with the transfer case in high range, is roughly equivalent to 1st gear of a T-90 with the transfer case in low range. Putting the transfer case in low range and the T-98 in 1st gear gives one a 'compound ridiculous low' that is good for going slowly over difficult terrain.
"I have taken advantage of the really low gearing on several occasions. If I stall going up a steep hill, I can put it in 1st gear low range, leave it in gear and work the starter. Normally I would have to set the brake, get the clutch disengaged, get the engine started, work the parking brake, the throttle and the clutch without stalling the engine again or sliding backwards. The gearing is low enough that the engine will start and I will get going again without any sudden jerks or strains.
"The disadvantages to the transmission are the difficulty in finding parts, the shorter rear driveshaft and slightly reduced ground clearance.
"I haven't looked too hard, but I haven't had as easy a time finding the parts for the T-98 as I did for the T-90. I've been collecting parts for a rebuild. So far, all I have left is the input shaft for the 4F-134 engine, and I think a reverse idler gear.
"The T-98 (top rear view at right) is quite a bit longer than the T-90 and the drive shaft must be shortened to slightly less than 12 inches to fit. Short drive shafts are tougher on U-joints than are longer drive shafts.
"The T-98 is 'taller' and this reduces ground clearance by a couple of inches. This is right in the middle of the Jeep though, and I've not had any problems with this. There are some spacers that fit between the Jeep's frame and the transmission support/crossmember. The spacers are 3/4 inch thick, 4 7/16 inch long and 2 7/16 wide. The holes are not drilled along the centerline of the width of the wood, but instead are drilled so that the edge of the wood is flush with the outside of the frame. The wood then extends past the inside of the frame, but this part of the wood is protected by the crossmember.
"The other difference that I've noticed with the T-98-equipped CJ-5 is that the transfer case levers (I have the dual lever transfer case) are more straight than those used when a T-90 transmission is installed. Also, the sheet metal making up the cover over the transmission is quite a bit different from a normal T-90-equipped Jeep.
"On my CJ-5, the frame already has holes drilled in place so that either transmission can be placed into the frame. Also, the ball stud that the clutch tube rotates on is mounted to the T-98 transmission-to-transfer case adapter, so that (I think) the clutch linkage remains the same for both transmissions."
See also a close view of the identifying number cast into the top (20K JPEG).
Ben Neil describes his Jeep philosophy: "I believe in changing the mechanicals to meet your needs but still keeping original Jeep parts and looks a priority. My 1950 3A was in the Nov. 2001 JP magazine. I was at Moab running all the 3 to 4-rated trails -- never faulted once. Restorations are for museums and speculators. If you are going to live with them everyday, enjoy 'em and make 'em work for you. Life is for living."
Bill Derkland installed the T98 as part of a beautiful six-stick tranny/TC/PTO setup in his '49 CJ-3A. Bill passed away in 2013, and as of 2014 his 3A restoration is being completed in his honor (see Bill's Willys.)
Ken Bushdiecker provided some detailed information:
"The T98-A was introduced as a CJ-5,6 option in 1956. The installation includes the following parts. Most but not all of these parts are needed for CJ-3B conversions."
10.22 Flywheel Housing
11.02 Clutch Control Parts
13.01 Exhaust System
18.02 Transfer Case
18.06 Shift Lever
18.08 Transfer Case Mounting
19.01 Propeller Shafts
24.01 Hand Brake
31.09 Floor and Underbody
31.14 Plates, Seals and Covers
"Here are some important factors that CJ-3B owners should consider concerning selection of the optimum transmission:
"First acknowledge that the CJ-3B is an early offshoot of the original JEEP LRV. The complete CJ version of the T90 weighs in at 60 lbs. The complete CJ version of the T98 with it's adapters weighs in at 160 lbs. This has a significant effect on an early Jeep's ultra-light curb weight.
"The T98-A will give your Jeep a painfully slow reverse gear as in 7.8 to 1 ratio. It's really overkill behind the Hurricane because it is so rock solid and big. But if you need a super low gear it's absolutely the way to go.
"When W/O installed 4.27 final drive gears into CJ models in 1962 they simultaneously changed from T90-A to T90-C -- see Change from 2.798 first gear to 3.34 first gear (120K JPEG). This significant gear reduction solves any potential clutch slip/engage issue. The T90-C provides a greater gear span than any other 3 speed (bar none.) Plus the T-90-C compound ranges with a Warn overdrive better than all other truck type transmissions. Better compound ranging implies that the transmission gears are split nearer to their midpoint.
"One drawback of the T90 is its non-synchronized first gear.If tires became so tall that a Jeep needs a 4-speed low gear on take-off, then that too is a a non synchronized gear.
"Another drawback of the T-90 is is somewhat limited strength. From what I hear, D-225 torque is not problem for a T90. But if one should opt for a V-8 engine power then the T15 is "the king of the hill",meaning the T-15 is above all other three speeds concerning strength.
"That said, the T90-C gearing span is "the best" but not as wide as any truck four speed. But then again; all truck 4 speeds are lousy concerning space and weight efficiency. Out of all older truck transmissions I vote the T90's as the best transmissions behind Hurricane engines. The T98-A is 2nd runner up when mated behind a Hurricane engine as it also compound ranges nicely with a Warn overdrive. The T90-C version is the hands down winner and should preferably be used with a 25% overdrive.
"The best transmission for a Dauntless powered early CJ is a very tough call indeed. But I am inclined to vote wide ratio Jeep T-18 as the best (modified length maindrive gear and Jeep D18/D20 cast iron adapter.) T15 three speed is my 2nd runner up behind a Dauntless (again modified maindrive gear.) And yes, the T-15 does bolt directly to the model 18 transfer case."
Herm Tilford wrote in 2014 to say, "I built the transmission and transfer case setup for Bill Derkland and was sad when his wife called and told me he had passed away.
"I decided to start a project with the T-98 transmission in mind. This transmission has the 15/16" input shaft and is a direct replacement for the T-90 3-speed transmission with the short shaft.
"One of the first obstacles that I needed to overcome was the front bearing retainer. It was bulky very expensive to machine and duplicate, but that meant changing the front adapter.
"The T-98 and the T-18 transmissions are similiar and the gears can be interchanged in the cases. The T-98 transmission case are not as available as the T-18 cases, therefore was there a way to use both bolt patterns of the two transmission cases?
"Yes, there was room to make an adapter with both bolt patterns. Then if I made the adapter the same thickness as the original and changed the center to accept the bolt pattern of the stock 4-cylinder front bearing retainer, I would be able to use the stock clutch linkage just like the original.
"There is a new T-90 front bearing retainer available with a poly seal instead of the felt and does a fine job of sealing with the new front shaft unlike the felt. So now I have an adapter with both the T-98 and the T-18 bolt patterns and a new front bearing retainer, that solved the biggest obstacle.
"Next I made an aluminum adapter that will accept a 3-1/4" or a 4" D-18 or D-20 transfer case. This way If a customer wants a tera-low transfer case it will bolt on.I purchased a factory CJ-5 with the T-98 running gear and copied the stock parts such as the oak wooden spacer blocks for the crossmember, duplicated the steel mount that attaches to the crossmember and the rubber mounts used with it, to make a complete kit. I spent a lot of time on this project but there were quite a few Jeepers that wanted this setup. I only sell it as a complete package."
The Rebuilt T-98 for 4 cylinder Applications sells for $1650 on Herm the Overdrive Guy's website.
Herm also has a rebuilt RTS Transmission with Overdrive (3+1) kit available for use as a heavy-duty transmission in Jeeps with larger engines including the V6.
Thanks to Ben for his photos and to Ken Bushdiecker, Eric Lawson and Herm Tilford for further information. -- Derek Redmond
See also CJ-3B Tech Tips on the T90 Transmission.
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