Engine Swap Advice

I've been thinking over the various engine swap choices for my early '5, and have done quite a bit of reading over at the Novak site. They have lots of good information there, but I'd like to get some opinions from you guys too.

I have an '01 Wrangler with the 4.0L motor in it. I've been very happy with that, but I know the in-line 6's don't fit well (or hardly at all) into the short nose CJs. So, I'm looking at the Dauntless V6, or a mild SBC V8. I would like to get a similar amount of power to what I get in my Wrangler, or just a little more. So, how does the Dauntless compare with the 4.0 in terms of performance? I'm only asking because I'm very familiar with the 4.0L motor, and what it can do in the applications I would use it for. It makes a good benchmark for me.

I've only noticed the 4.0 being a little weak at high elevations under stressful conditions, such as in deeper snow with tire chains. I know a V8 would cure that, but I'm not sure I want to bother with the extra complications of a V8 swap. In particular, I'm hoping to install the new motor without moving the transmission crossmember. I don't know if that will work out, but it sure would make life a little simpler. Any thoughts on how that could effect my engine swap choice? I have a stock T98, the D18, and the 4 cyl.

Thanks in advance for your help and advice.

 

When Jeep installed the T98A into a CJ the rear engine support crossmember was moved back exactly 5-1/2" from standard.
The front propeller shaft was roughly 5-1/2" longer while the rear propeller shaft was exactly 5-1/2" shorter than standard.

When Jeep installed the Dauntless engine into a CJ the rear engine support location remained the same as standard.
T86AA and T14 propeller shaft lenghts vary from standard because the transfer case is not positioned on true crossmember centerline.

If you use T98 propeller shafts you will also want to use the T98 crossmember which positions the transfercase on crossmember centerline.

Mating the T98 to the Dauntless will be your main concern.
You will need to change the maindrive gear to a Jeep 1-1/8" diameter maindrive that has been modified to a custom lenght.
The exact lenght depends on the bellhousing depth and bellhosing adapters if any.
Or consider installation of a Ford T98/T18 having 1-16" diameter maindrive.
If using the 6-1/2" stickout Ford maindrive all bellhousing adapters must be eliminated.

The selection of specific transmission, adapters and bellhosing is critical.
Too long OAL and the radiator is compromised. Too short OAL and the firewall hits the Dauntless left valve cover.
I have done exacting measurements/calculations for a Dauntless with T98 into a CJ-3B but the engine location specifics are not the same as the CJ-5.
Stock Dauntless front engine support brackets for a CJ should also be considered.

 

I knew this would be a slightly more complicated undertaking because of the Jeep T-98. I really like that trans, and would hate to get rid of it, but it almost sounds like keeping it could be more trouble than it is worth. A lot of people here seem to like their SM-type transmissions.

All this almost makes me want to find a fresh F-head to replace the L-head the PO put in there. But I think that swap would have limited benefits, so I haven't put much thought into it for awhile. I think it would be disappointing in the mountains....

(Don't worry, I know not to even try putting a 4.0 in there!)

 

I think the main problem with the T-98 will be the short stickout of the transmission. I believe the F134 bell is rather shallow, so you don't have a lot of length to work with if you want to adapt a different bell.

A T-18 is quite similar to the T-98 (the T-18 was derived from the T-98) and fit and function would be basically the same. It is fairly easy to adapt a T-18 to a GM bell, so that would give you quite a few choices, covering both Ford and GM.

If you want V8 power in a V6 package, I think you'll want to look around a little at some more modern engines. The 225 and 231 are fine engines, but engines have improved a lot since they were current. Certainly a 225 in a CJ-5 chassis would provide enough power for me, but it does not compare with the 4.0L HO or modern small-displacement V8s.

 

The L/F 134 supply excellent torque and acceptable HP for most offroad situations.
They are durable and extremely forgiving engines.
If your used to a Go Devil the Hurricane will be a big improvement in HP.
However the Hurricane will not effectively/efficiently produce abundant HP which is basically tied to discplacement.
A Hurricane can certainly produce lots of HP but to do so is a serious lesson in economics.

The T98 and T18's are exceptionally well built transmissions.
All Hurricane powered Jeeps having T98A use 15/16" diameter, 10 spline.
All 6+8 cylinder Jeeps with T98 use 1-1/8" diameter, 10 spline.
All Jeeps with T18 are also using 1-1/8" diameter, 10 spline.

 

The T-98 was used in old Ford pickups ... any idea if the gears match? That might be a way to get the stickout you need to use a Buick bell and a plate ... or maybe just a redrilled bell.

 

The Ford T-98s I have seen use a big 1 3/8" input shaft. The stickout looks similar. Might limit your clutch choices though.

I'm with the other poster though, use an SM420 or SM465. You could probably finance the swap by selling the T-98 to another L or F head owner.

 

Well there are many considerations to acknowledge. Here are a few...
# 1 T98 vs T18 (For now lets just say I am inclined to like the T98 over the T18 for personal reasons)
# 2 The maindrive diameter (this basically effects ones choice of driven disks)
# 3 The maindrive length (this basically effects ones choice of bellhousing, adapter)
# 4 The maindrive gear tooth count. (You can swap around any length of maindrive so long as the make and the tooth count remain constant. The 15/16" diameter T98 maindrive used for F-134 has 17 teeth and can only be swapped with another 17 tooth maindrive gear regardless of length or diameter.)
(In at least some cases you can swap across from on make to another. For example I have a Jeep T18 with a short Ford maindrive installed.)
# 5 Ford, IH or Jeep ? (this mainly effects the bellhousing bolt pattern and potential PTO useage. A Fords PTO port is in the wrong place for a Jeep)

 

One of my concerns has been the overdrive and rear pto. I spent a lot of time getting those installed and working. I will not hijack my own thread with those stories, but I'd rather not undo all of that if I can avoid it. That's a reason in my mind to keep the T98 if I can. I'd almost rather swap in an F-head than undo/redo all of that.

If I end up having to switch out a mainshaft in the T98, can that be done without needing an overdrive with a different tooth count? Would it have to be removed? (I'm guessing I know the answer to that one!) Luckily I was smart enough (just barely) not to have a pto drive shaft made until after everything else is done.

Thank you all for sharing your knowledge with me; it is really impressive how much the people on this forum know about these matters.

 

T-18 and T-98 input shafts (maindrive) do not interchange even if the tooth count is the same. They have different sized pockets (where the tip of the output shaft rides). While not impossible, you must use a corresponding output shaft which also has some differences where third gear rides so you must use a T-18 third gear as well. I found this out the hard way. I tried to swap a 15/16" diameter T-98 shaft for a 1 1/16" diameter T-18 shaft, details are here and here.

 

The overdrive and PTO attach to the transfer case. The only fly you could put in the ointment is if you were to use a transmission with a 10 spline output rather than a 6 spline. Swapping the input shaft on your T-98 wouldn't affect that and neither of the adapters for the SM transmissions use a 10 spline, so other than possibly adjusting driveline lengths and the holes in the body where the shifters come through, the OD and PTO shouldn't be affected.

 

Grandpa Jeep
Exactly true. While I did not S P E L L it out thats why I posted T98 vs T18 as being # 1.
Make that decision first and you will avoid the T98/T18 trans-model (cross model) interchanges.
There are some parts that will interchenge between T98 and T18 and many parts that will not interchange.
Your link to internal comparison of T98/T18 is an excellent example albeit far from complete.
Swapping parts between "makes" (Ford /IH /Jeep) is a seperate issue even though both were "maufactured" by Borg Warner.
When "trans-model" or "trans-make" internal interchanges occur it becomes mandatory to address the specific components.

I see absolutely no reason to change the mainshaft. IMHO Your original 6 spline mainshaft is the way to go.

While were on the topic I'd like to EMPHASIZE for those who are attempting to comprehend.
It's easy to confuse the following transmission terms so....HEADS UP !
The term MAINDRIVE GEAR is the correct term. This is often referred to as the INPUT, the INPUT SHAFT or INPUT GEAR.
A similar correct term is MAINSHAFT. This is sometimes referred to as the OUTPUT SHAFT.
We often hear mention of the MAINSHAFT GEAR. This gear serves as the transfer case input.

 

THANK YOU!

i have had more than one encounter with people calling a part 6 different (slight exaggeration) names while trying to give me good advice,
and none of those names were in my FSM!