Does Vin Tell Gear Ratio? Or Any Other Clues

[DaveB26]

I  bought a 1987 Comanche a few weeks ago and have not seen it yet it is at my uncles place about 10 hours away from me so it won't be home with me for about two more weeks, I have been looking at whatever I can on this site to learn as much as I can about it .

 

so here we go ... I need to figure out what to do to make the thing into a little beast

 

what I know for sure is

1- the floor has been redone not sure about the quality of repair.(skeptical)

2- it is the 2.5 liter with 4X4 and a 4 speed stick (AW4) ? motor runs good according to my uncle and it had a new clutch last year according to the receipt

3- its red and has no tailgate (no problem I got one locally to put on when it comes home)

4-its getting a 6 inch Rubicon lift with control arm drop brackets, the axle flip to under spring, T case drop .and adjustable track bar ( not sure about shocks yet) waiting to do more research here and other places first.

5-allready have 1999 doors, front fenders, hood and grill assembly with wiring harness to go on as well. ( I have been bored waiting for this thing )

it better show up soon or I may hit the JY again and who knows what I might drag home.

6-really confused about what gear ratio might be in the diffs, from what I have always heard the 2.5 almost always have 4.10,  But then I just read the 4 speed stick is sometimes used with a( gas saver) package?? and the ratio might be 3.31 or some other garbage high ratio. 

7- the gears are going as low as I can 4.88 I believe I just want to be prepared with new carriers if they are needed because of the carrier splits in the axles.

8- looking at trying 33/10.50/15 BFG ATs and MT on stock turbine rims so this gear ratio thing is pretty crucial to me

9 of course I will be looking at brakes and changing all fluids before this thing gets too far along

 

VIN is 1JTHX6315HT012529   can anybody tell me anything about this trucks equipment from the VIN?  previous owner claimed it was a chief , I have a pretty clear idea that its not a chief (basic model is more likely)

[DaveB26]

DUH I just figured out the trans is not AW4 it is a stick shift not automatic

[Pete M]

don't put any money into regearing a dana 35 rear axle. go find an MJ/XJ dana 44 or XJ 8.25 or Explorer 8.8 and invest your money into an axle that will last. :thumbsup:

 

likely the ratio in the axles is 3.55 (most common ratio found in a 2.5L/4spd stick).  the trans would be an AX-4.

[Eagle]

A 2.5-liter with a 4-speed manual (AX-4, not AW4) will have 3.55 axle gears. 4.10s were used with the 2.5L and the 5-speed.

[MancheKid86]

there is a data tag bolted onto your axle diff cover,

it will tell you your gear ratio

[mvusse]

X3 on 3.55 gears due to 4 cylinder/4 speed stick shift (AX4)

 

Throw the transfer case drop kit in the garbage. With as long as the drive shaft is in an MJ it is not needed, it will put more strain on your engine mounts causing them to fail sooner and it will make the front drive shaft angles worse. It could also induce driveline vibration due to incorrect u joint angles.

[DaveB26]

A 2.5-liter with a 4-speed manual (AX-4, not AW4) will have 3.55 axle gears. 4.10s were used with the 2.5L and the 5-speed.

Well I guess the gear splits are going to be wrong for both diffs, too bad i was hoping to get away with keeping the carriers when rehearing to 4.88, on the bright side if it can move along at all with 3.55 ratio on stock tires it should do okay with 4.88 ratio and 33s

[DaveB26]

X3 on 3.55 gears due to 4 cylinder/4 speed stick shift (AX4)

 

Throw the transfer case drop kit in the garbage. With as long as the drive shaft is in an MJ it is not needed, it will put more strain on your engine mounts causing them to fail sooner and it will make the front drive shaft angles worse. It could also induce driveline vibration due to incorrect u joint angles.

I was wondering about the front drive shaft angle getting worse while (improving) ? Rear-drive shaft angles , glad you spoke up on that, I guess I can leave it off and try it with out first maybe. Any other advice ? Don't be bashful!

[DaveB26]

Another thought I had was to use the 255/85/16 mudders from my super duty and put some new shoes on it instead of buying the BFG 33s I wanted I really like the narrower tires in snow and mud and the 255s are pretty tall 32/33ish

[DaveB26]

don't put any money into regearing a dana 35 rear axle. go find an MJ/XJ dana 44 or XJ 8.25 or Explorer 8.8 and invest your money into an axle that will last. :thumbsup:

 

likely the ratio in the axles is 3.55 (most common ratio found in a 2.5L/4spd stick).  the trans would be an AX-4.

I would love to find a D44 from xj or mj but there is only one Comanche in junkyard around here that I am aware of and I already looked under it D35 rear, lots of XJs but they all seem to be the 35 or the 8.25. I really want the D44 but its like looking for a unicorn!

[mvusse]

Don't shy away from the 8.25". The 97 and newer ones have 29 spline axles and are pretty much equal in strength to a D44. The 8.8 is a good axle also, but you will need to adapt the pinion to a 1310 u joint and have ti run wheel spacers. It may only be 1 inch narrower than an MJ/XJ/ZJ/YJ/TJ axle, but with the wide @$$ of a Comanche, that 1" will cause problems with the inner walls of the fenders.

 

If you are looking to regear, gears ($200), master install kit ($100), labor ($300) per axle, a carrier ($70) is only a drop in the bucket. Also with 4.88 gears in the front axle the pinion is so freakishly small it will be very weak due to minimal teeth engagement. There is a reason Spicer doesn't make 4.88 gears for a Dana 30. I would not go lower than 4.56 on a Dana 30. 4.56 gears with a 33" tire still gives you a better final drive ration than your stock 3.55 gears with the stock tires which are most likely 205/75R15 or 27", but possibly 225/75R15 or 28" even though it will currently most likely have 235/75R15 or 29" tires.

 

The MJ Dana 44 is not like a unicorn, it IS a unicorn. And because of that when you do find one you will be paying a premium price for it, more than it's strength alone justifies when a 29 spline 8.25" can be had for $100.

 

Edit: I have been called a number of things over the years, but with 5,965 posts on here, bashful was never one of them.

[DaveB26]

So now I will be looking for 8.25 axle to replace the D35 and will need to do some math before I settle on 4.88 or 4.56 , the gear swap will be needed for sure just to help it get out of its own way. I want to come close to factory gearing or lower. This little truck won't see long stretches of highway time unless we tow it some time. But I do see it having some fun playing in the rocks and desert around here.

[Pete M]

car-part.com can help with finding junkyard axles. :thumbsup:

 

and I recently got another 44 for all of 89 bucks.  they are out there. :yes:

 

U-joints don't like changes in their operating angles so you might be changing them in the driveshafts (especially the rear). 

[mvusse]

So now I will be looking for 8.25 axle to replace the D35 and will need to do some math before I settle on 4.88 or 4.56 , the gear swap will be needed for sure just to help it get out of its own way. I want to come close to factory gearing or lower. This little truck won't see long stretches of highway time unless we tow it some time. But I do see it having some fun playing in the rocks and desert around here.

 

As I stated in my other reply, 4.56 will already gear your truck lower than it is now, and 4.88 will sacrifice strength in the front axle.

[DaveB26]

_{I like the 4.56 idea much better that 4.88 pinion looks a bit weak!!  but also I will be scanning the JY for 98 and newer Xj 8.25 rear axles  I did kind of have in my mind the D35 could survive behind a 2.5 pretty well but a cheap upgrade is always cool too.}

[01yellowxj]

On the xj rear axles there is also a white sticker on the axle tube that has the ratio if the tag on the pumkin is gone.

I am a XJ person and just got a MJ so I'm learning. Not sure yet if I got a good one or not. No AC sucks if I want to make this my daily.

[DaveB26]

Yea, I think the XJ is really a cool rig too I had an 86 Laredo 4 door a few years ago 2.8 with 5 speed trans was ok at first, but once I installed the mandatory (for me) lift and 31/10.50 tires it was severely underpowered/under geared, never spent the extra cash to re gear it but did a Chevy small block/700r4 swap, this thing was awesome then, wish I still had it but I sure couldn't ever get past a smog test today with that V8, oh well I'm looking forward to the MJ project now and maybe I'll find the right 2 door XJ someday to park beside the MJ.

[carnuck]

I know the 4 speed XJs 84 to 87 came with 3.73 pretty commonly. I have one in my Comanche SOA now. After I get the 8.8 with 4.10s in, I'll be pulling the matching vacuum front and putting in a non-vac with 4.10s then selling the complete 3.73s. (price on the truck will go up too though)

[48MJ]

I've seen many swapped axle gears miss labeled I'd check the stamping on the ring gear to be sure. It's a hassle but at least then you know for sure.

[dasbulliwagen]

Once you do all these mods, you'll then be wanting for power again, even with the regear. I have a 2.5 with four.10 gearing and really notice when I have a little weight in it... makes a big difference. I'm getting ready to install a set of JK take off wheels and am not looking forward to the loss of what little power I have. I have done a couple of upgrades to the engine. Ive 'freeflowed" the cat conv, added a Flowmaster 50 series muffler, removed the engine driven fan and install a thermostatic controlled electric one, and did a "cold" air intake tube (modified from another vehicle). These all helped a little but you may still not be happy. Just remember that its only a 2.5, the little (older) brother of the 4.0. It will get you where you want to go, eventually!

[DaveB26]

Once you do all these mods, you'll then be wanting for power again, even with the regear. I have a 2.5 with four.10 gearing and really notice when I have a little weight in it... makes a big difference. I'm getting ready to install a set of JK take off wheels and am not looking forward to the loss of what little power I have. I have done a couple of upgrades to the engine. Ive 'freeflowed" the cat conv, added a Flowmaster 50 series muffler, removed the engine driven fan and install a thermostatic controlled electric one, and did a "cold" air intake tube (modified from another vehicle). These all helped a little but you may still not be happy. Just remember that its only a 2.5, the little (older) brother of the 4.0. It will get you where you want to go, eventually!

[DaveB26]

I do understand its a 4 banger. Not really looking for crazy power and speed. Just general drive ability and some slow off road trail riding mostly, if it becomes an issue then we will toss in a small block or a 4.3 Chevy V6 down the road.