Just Got my 86 Comanche

[tmmoll]

Alright, Well I finaly got the wifes approval after selling my old Beetle to buy a 1986 Comanche 2.5l 4wd. Ive had alot of jeeps in the past but no 4 bangers. I do have acouple of questions about these jeeps though. First off my plans for this is its going to be a dual rig. Great for on and off road conditions. Now eventually I will be swaping the 2.5 and 4 speed for a 4.0L HO and an AX-15, but thats going to be down the road.

 

A question that I had is that will the 2.5 hold up to 33-35in tires? Again this maybe for about a year until I swap. And the interior is a liitle ugly. I had seen on shelbyluvvs build up page that they swapped the interior for a 97+. Are there any more references for this? I think it looks sweet with a newer cherokee interior. Any info would help.

[mjeff87]

I ran 33's on mine before I swapped the 4.0 in.....with 4.56's.....no fun on the highway. No fun whatsoever.

 

Jeff

[Mr_Random]

You won't be able to swap the 4.0 without alot of modification, unfortunately. Unless the XJs and MJ's of the 86 year had different firewalls, you'll have to severly modify yours. Might as well do a 4.3 swap or something similar.

 

Even with 4.88's I've read that the four cylinder will hate those 35's, not to mention you'll need at least a new rear axle to accommodate the big tires...

[mvusse]

I've heard the firewall just needs to be modified 1/2"; a few good hits with a BFH should do it. Although it is rumoured some of the later 86s already have the newer 87 and up firewall.

 

And yes, I've heard the 2.5 is gutless on stock tires. I have seen 35 under a Comanche and think they look too big, but even with 33s you'd probably need to run at least 4.88 gears. With a 4.0 you should be okay with 4.10.

[Eagle]

4.10s won't be enough gear for 33s or 35s with a 5-speed, not even with a 4.0L.

 

My rule of thumb is 3.73 for 30" tires, 4.10 for 31" tires, 4.56 for 33" tires, and 4.88 for anything larger.

 

And it never hurts to go one gear beyond those, but backing off one ratio (taller) is probably a mistake.

 

IMHO, simply forget about running anything larger than 30" tires with the 4-cylinder.

[JeepcoMJ]

I've heard the firewall just needs to be modified 1/2"; a few good hits with a BFH should do it. Although it is rumoured some of the later 86s already have the newer 87 and up firewall.

 

And yes, I've heard the 2.5 is gutless on stock tires. I have seen 35 under a Comanche and think they look too big, but even with 33s you'd probably need to run at least 4.88 gears. With a 4.0 you should be okay with 4.10.

 

not to mention that the entire radiator support is different and must be physically cut out of the vehicle to swap in the 4.0 radiator support. also the front frame crossmember needs to be swapped, and the front portions of the inner fenders do not match.

 

the firewall issues are a myth.

 

 

anyways you may have an amc20 rear axle in that truck. snap a pic and post it on here, we'll tell you if it's a dana 35 or amc20 unless you already know. a single piece shaft amc20 is equal to if not stronger than a dana 44, and would hold up to 33" tires. you need 5.13 gears at least to pull off the 33's with a 4 cylinder.

[jtdesigns]

Bad thing with the AMC20's is the two piece axles. I think crown and some others, makes a one piece though..

[JeepcoMJ]

Bad thing with the AMC20's is the two piece axles. I think crown and some others, makes a one piece though..

 

mj's had one pieces...i pointed that out already. cj's had two-piecers.

[jtdesigns]

Bad thing with the AMC20's is the two piece axles. I think crown and some others, makes a one piece though..

 

mj's had one pieces...i pointed that out already. cj's had two-piecers.

Good deal.. I hated the two piece axles.. Spun two. First one torqued it down to 250 ft/lb as told, a week later spun it,, second one went to 325 ft/lb and never had a problem with it.

[tmmoll]

I know that this is a d35/d30 combo. I will end up swaping some day. As far as all the fabwork for the 4.0, would it be better to swap a different 6cyl? If so how hard would that be?

 

How about the interior? Anybody have any news on that?

[Eagle]

I know that this is a d35/d30 combo. I will end up swaping some day. As far as all the fabwork for the 4.0, would it be better to swap a different 6cyl? If so how hard would that be?

The firewall may or may not need to be modified. Most people who do a 4.0L swap into an 86 or earlier XJ or MJ do have to modify the firewall, some don't. Jeepco is correct about the front end -- the entire radiator and support structure is different for the 4.0L.

 

The easiest 6-cylinder swap is a GM 3.4L from a rear wheel drive Camaro. It's the same block as the 2.8L that Jeep used in 84 thru 86, so all the brackets and "stuff" you'll need are available without custom fabrication.

[Phoenix of Fury]

I've got an '86 with the 2.5L. I'm running on 33's with 4.88 gears front and rear. It's definitely lacking power during uphill climbs at higher speeds, but at lower speeds you can drop gears and gain the power back. It's not horrible horrible, but it's far from great. I'd give it a 4/10 on whatever scale it is that popped into my head.