Drivetrain opinions

[evesdropper]

Hello,

I am finally getting around to working on my 1984 CJ8 I picked up a few years ago. I would appreciate some advice on how to proceed.

The scrambler is powered (if it was running) by a 2.5l AMC mated to a T-5 and Dana 300 . The motor ran when I got it but very poorly. This was due to a tank full of several year old gas. 80,000 miles.

I have available a unknown milage/condition AMC 304 mated to a T-15 (?) with no Transfer Case . I don't have any of the accessories or brackets for the AMC 304 .

The Jeep will be driven 80% of the time on paved or gravel roads. The rest of the time it will be me and my boys camping vehicle. Mostly dirt and mud tracks.

What I have already done:

• new stainless fuel lines
• dropped the tank and power washed it out
• new rollover valves and pickup/sender unit
• heavy duty welded tank skid plate/box
• Nutter bypass on the carb

I would like to hear opinions on finishing fixing the 2.5l vs the AMC 304 as the power plant. I am leaning towards just finishing the 2.5l and save the money for the body. Thoughts?

 

[Lumpy Grits]

Do you have any SMOG laws to deal with?
LG

 

[evesdropper]

Absolutely none. Other than I am supposed to leave the cat converter in place. I will have to buy a new one either way. mine was rusted out with the rest of the exhaust.

 

[Woolyworm]

I had a 4 in a mid 90s YJ and I have a AMC 304 in my CJ now. I wouldn't swap back to a 4 that's for sure. But you'll need to decide if it's worth the conversion work. I say yes but I'm not the one doing it so that's easy for me to say. I think there are some trick to pulling a little more power from the four as well.


Wooly

 

[hole]

Evesdropper, what are your plans for tires, at least size anyways? If you plan to stay close to stock and dont have too many steep grades to contend with regularly the 4cyl would do the job. The T-15 was mated to a Dana 20 transfer-case, so you'd have to scrounge one up along with all the AMC 304 accessories you'll need if you go that route. You might want to consider keeping your eyes peeled for a AMC 258 i6 / 4.2l I6 , direct bolt in and can generally be found fairly cheap.

 

[Lumpy Grits]

You will like the V8 way more than that gutless 4 cyl.
LG

 

[evesdropper]

Evesdropper, what are your plans for tires, at least size anyways? If you plan to stay close to stock and dont have too many steep grades to contend with regularly the 4cyl would do the job. The T-15 was mated to a Dana 20 transfer-case, so you'd have to scrounge one up along with all the AMC 304 accessories you'll need if you go that route. You might want to consider keeping your eyes peeled for a AMC 258 i6 / 4.2l I6 , direct bolt in and can generally be found fairly cheap.

I don't see myself going much larger than stock tires and there are no mountains in Iowa. You bring up a good point about the Dana 20 . I don't have one currently. I assume I would have to deal with driveshaft changes as well if I go that route.

Will I need to torch off the 4cyl motor mounts and get some 6cyl ones or are they the same? (nevermind. Napa cross reference has the same mounts for both.)

 

[Lumpy Grits]

Engine mounts are different, and in a different location.
The frame has the holes already punch'd.
LG

 

[HackFabrication]

Thoughts?

I'm going to take the other path and recommend you keep the I4/T-5 /Dana 300 combo. Lot's of reasons for this, that I'm certain other's on this forum will be happy to pick apart, but here goes:

You already have it - You don't need to go and find anything.
It already is installed in the vehicle - You don't need to 'modify' or 'adapt' anything.
Sticking close to stock will make everything easier. Easy saves $$$.

You have stated you plan on near stock tires, but you should check your axle ratios anyway. Jeep liked to put 2.73's in the later CJ's. Dropping to a 3.31 or 3.54 and running a 30-31" tire would make the I4/T-5 happy. And most likely you can continue to run the 2-piece axles, until you get into the gearing, which is a good time to upgrade.

Although the 'Iron Duke' I4 would be my personal preference in a 4 banger, you should be able to squeeze some better hp/tq out of it with a few add-ons. Do some research and see.

T-5 transmissions die from big hp/tq, big tires, and bad gearing. In any combination, or separately. However, properly maintain, utilized within it's limits, it should be okay for what you have planned. It often gets a 'bad rap', but a lot of it isn't deserved.

 

[Bent]

I had the Iron Duke in my CJ5 for awhile. Loaded with kids and camping gear it was totally inadequate. I doubt the AMC 2.5 will be much better.
When AMC introduced the 2.5, they kept the GM "metric" bellhousing pattern because they were already using the GM 2.8 in the Cherokee. So, there are a few options that will bolt up to your bellhousing with out an adapter. The Buick 3.8 was produced with the metric pattern and would be a good fit for your application. If you go with the I6 you will need to move the Transmission back and have the rear drive shaft shortened and the front lengthened. V8 might require a Transmission swap.

 

[Woolyworm]

Poke around on Craigslist or whatever you have there. I picked up a good I6 with a jeep T-18 and Dana 20 on it for $500! All in great condition. You could slide that whole rig right in. Or look for a parts rig and buy that cheap and swap it. Just a thought.


Wooly

 

[Neuner]

Jeep liked to put 2.73's in the later CJ's. Dropping to a 3.31 or 3.54 and running a 30-31" tire would make the I4/T-5 happy. And most likely you can continue to run the 2-piece axles, until you get into the gearing, which is a good time to upgrade.

With the 4's I thought they put in 4.10's. Then and now, 4's need higher revs to get adequate power and one of the reason's they fry early.

 

[HackFabrication]

With the 4's I thought they put in 4.10's.

If he has 4.10 gearing, that would be great.

 

[evesdropper]

Thanks for the advice so far. I will check the stamp on the axle housing tonight if I can read it.

I am leaning towards the i4 since as it was mentioned, I have it already. Not much in the way of upgrades available for it though. The inertia ring from Tri-County Gear wont fit this year model according to them. I could get a cam from Clifford, Yella-Terra or Sharpe roller rockers and put on a weber carb. That is about all I could find to do. I could sell the AMC 304 and T-15 for upgrade money.

Regarding the bell housing comments, I thought that the housing changed from the chevy pattern when AMC started using their own i4 instead of the iron duke? I was under the impression the only direct bolt-on to the housing I have would be the AMC engines. I am new to this so I could be wrong.

 

[Bent]

Thanks for the advice so far. I will check the stamp on the axle housing tonight if I can read it.

I am leaning towards the i4 since as it was mentioned, I have it already. Not much in the way of upgrades available for it though. The inertia ring from Tri-County Gear wont fit this year model according to them. I could get a cam from Clifford, Yella-Terra or Sharpe roller rockers and put on a weber carb. That is about all I could find to do. I could sell the AMC 304 and T-15 for upgrade money.

Regarding the bell housing comments, I thought that the housing changed from the chevy pattern when AMC started using their own i4 instead of the iron duke? I was under the impression the only direct bolt-on to the housing I have would be the AMC engines. I am new to this so I could be wrong.

The Iron duke that was put in the cj (at least the one I had) used the Chevy V8 bellhousing pattern. The iron duke in the S10 and Camaro use the metric pattern. The AMC 2.5 also used the GM metric pattern and not the AMC V8 pattern.

 

[evesdropper]

The Iron duke that was put in the cj (at least the one I had) used the Chevy V8 bellhousing pattern. The iron duke in the S10 and Camaro use the metric pattern. The AMC 2.5 also used the GM metric pattern and not the AMC V8 pattern.

Thanks for clearing that up for me. If I understand correctly then, fixing the i4 is my lowest cost option. Swapping for a AMC 258 i6 / 4.2l is going to require at minimum a bell housing that can mate to the amc pattern on the AMC 258 i6 / 4.2l and whatever the T-5 pattern is. same for the AMC 304 unless I use the T-15 and locate a Dana 20 TC.

I cannot find the axle code stamp on the rear axle due to rust and the same runs has rendered the tag on the front axle unreadable.

 

[Neuner]

Time to count some rotations.

 

[Bent]

If you keep the 2.5, check out the flywheel inertia ring that the Cherokee guys are using.
I6 will also require new drive shafts because it moves the Transmission /Transfer Case back to the next location on the skid plate.

 

[Only in a Jeep CJ]

The Jeep will be driven 80% of the time on paved or gravel roads. The rest of the time it will be me and my boys camping vehicle. Mostly dirt and mud tracks.

Based on that alone Id lean toward a 4.0 with the fuel injection. As said, the frame is already drilled for the mounts which are free to cheap and easy to find. The AMC 304 /T-15 can to sold to offset the 4.0 purchase. If done right, it can even be a wash at that point. You have the Dana 300 so you will only need a Transmission /bellhousing and driveshafts. The sell of the I4 and T-5 can help offset that too. For a stock bolt in deal, a Transmission from a 6 cyl application will have the 10 spline input. T-176 , T-4 /T-5 or AX15/NV3550 with an adapter will work.
In the end, you'll have a more powerful engine with reliability. Coast CAN be kept down with your other items for sale. Then you can focus on the body.
If all of that is too much for you, then I second the fixing the I4 as it is already there.

 

[evesdropper]

Thanks for the help and info everyone.

This sounds like a bigger project than I anticipated and FI is beyond my technical abilities at the moment. I will focus on getting the engine running well and then move on to body work.

If you are looking for a AMC 304 /T-15 , I will post it in the classifieds soon. Thanks.