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The Various Myths 

vs. 

Actual Observations 

of 

Powertrain Swaps into Jeeps

1. "My axles are not strong enough for a V6 / V8."

Not usually true. Your Jeep axles may not be strong enough for your seriously oversized tires, or a totally untrained throttle foot, but the engine itself with good driving on most terrain will not require axle changes.


2. "V8's are for testosterone overaged punks with power complexes."

Our experience has been otherwise. Many very mild and refined individuals call us wanting a good engine. Testosterone and other manhood related jokes to engine size don't seem to apply. However, how people use their V8's day-to-day may or may not always do them credit.

3. "V6 & V8 engines get poorer mileage than I4 and I6 engines."

In fact, the opposite is usually true. An article of interest is found here.

4. "Mopar/Chrysler engines install into Jeeps easily since they are now the same company."

We used to wish that this was true, and we, other companies and our customers found out otherwise. GM engines feature broader compatibility and easier install-ability and for less cash outlay.

5. "The I6 is a torque monster" or is "a better off-road or pulling engine than a V8."

No. While there are some inherent smoothness and basic torque advantages to many I6 designs, they usually don't have the torque or broad usability (meaning wide torque & horsepower curves) that good V6's and V8's have.

6. "I have to do a body lift, or firewall or grill modifications to fit a Chevy engine."

No. In fact, we can think of no Jeep swap we've ever done in our facility or where we've spoken with (literally thousands) of customers about theirs - where a body lift was required. Other companies have claimed that a body lift is needed. These companies need to install their engines/transmissions in the correct location and restate for the record.

Firewall mods are extremely rare and grille mods are unlikely.

7. "I'd like to install a Jeep / AMC engine so that it is consistently all Jeep parts."

Ok. If you are really going to stick to this conjured rule, then you will need to ditch these factory supplied components:

GM

Hydramatic transmissions 
Buick engines 
Chevrolet engines 
Saginaw power steering
Steering columns

Ford

Starters
Ignition systems
Warner transmissions 
Tremec transmissions

Chrysler

Torqueflite transmissions

Renault

Renix EFI control systems

Good luck with that.

Some folks mask cheapness ("I got this free engine") with brand loyalty and get a swap that, in the end, achieves neither.

Some of the hardest parts to swap into Jeeps are usually Jeep parts. Counterintuitive? Absolutely. Yet, parts interchange between Jeep powertrain components is usually difficult, occasionally nightmarish and the benefits are usually unsubstantial and unjustifiable in terms of the effort and expense they create.

8. "I have this free engine I got from a buddy, and would like to swap it into _____."

"Free" can be surprisingly expensive. Chances are, they were free for a good reason. If you're luckier than we usually are and it happens to be a free GM, Ford or maybe a Dodge engine, than you're starting to get warm...

9. "I want to do such & such swap this way to be different."

Wear strange clothes and attend bizarre conventions if you want to be different. We're talking about an engine swap here. Swap the motor because it makes good mechanical and economic sense. Making a statement here will probably cost dearly in time, cash & nerves. Tried and true is very valuable.

10. "There must be some combination of really good components can I put together without adaptation?"

There are virtually none, otherwise adapters and adaptation would probably not exist. Of course, you don't have to put any more stock in this statement than you do the laws of economics.

We use adapters, the factories used adapters - it's about getting the best stuff to fit together to build the best Jeep for your needs.

Good aftermarket adapters don't just adapt, anymore. They offer more compact, stronger, better clocked, better mounted powertrain systems.

11. "I know I have a weak transmission, but I'll be nice to it with my new V8."

Just stop and think about this for a minute. We'll spare you our response here, and then recommend you take the hyperlink to Conversions We Don't Do.

12. "More splines mean a stronger shaft."

Not always. Two issues are at play here: smaller (and numerically more) splines on a shaft are less expensive for manufacturers to roll forge in lieu of cutting the larger splines, thus the use of, e.g. 32 splines (rolled) in place of 10 splines (cut). It is the actual shaft diameter that has the largest effect on shaft strength. As another myth-defying example; a Jeep 23 spline shaft has a slightly larger minor diameter than a GM 27 spline shaft.

13. "Cradle/crossmember engine mounts are stronger than side mounts."

Maybe they are, but whether that matters in a practical sense is the real question. The engine itself is a crossmember, given the right mounts. Jeep frames are typically plenty strong and all of them already feature a factory crossmember just under the grille - only inches ahead of the engine mounts location. Crossmember mounts were used in the 1960's and 1970's, but have largely fallen out of favor with conversion tech's. Installers usually regret using cradle mounts, especially in terms of exhaust clearance, steering clearance, engine service, etc.