I have a problem and was hoping somebody out there could help me out. Ok here we go. I bought a 1991 cherokee 4dr 4.0 auto that needed a new motor so i found a 1988 2dr 4.0 auto i figured i could use it for the block because i know there was alot of changes between the years. Now my question is when putting the flex plate and torque converter back on does it matter what one i use. I put the 88 on do to thats the motor i use but i dont know about the tranny. I put it in and its not even rolling over to bolt the flex plate to the converter. so other than the crank sensor being different is the bell houseing different or is it the flex plate holding me up. Sorry so long im just frustrated with this truck any help would be great guys. Thanks

 

Not 100percent sure... but i would use the flex plate from your old setup that way it will mate with your trans and the ckp sensor should work fine, I don't think there were any changes to the bellhousings

 

the 88 will not work on your 91,you have to use the 91,if you look at them you will se the diff in the size of holes on the two different flexplates,the tone ring on the 88 is square,the 91 is long rectangular and further apart,just put your 91 flexplate on and make sure torgue converter is all the way on your trany and all will be good,you cannot use the cps from the 88 on your 91 harness. When it comes to xjs,just remeber that in 91 chrysler switched from the renix to there control system,and 91 was the first year of the h.o motor. Another item you may find harder is bolting your intake and exhaust to the 88,if possibible use the head from your 91,it is a much better head,it flows better. I went the other way and put a 91 in my 89,works good.

 

Thanks guys. Im going to be pulling it back out tomorrow and switch them out. I had a feeling i need to put the 91 flexplate on but i just didnt. o well you live and learn right. lol I will let you know how it all works out. but one other question other than the intake what else changed on the motors minus the obvious like t stat housing and coil placement.

 

the things that changed from 90-91 are,new better flowing head 7120. new high profile cam,this allowed chrysler to get rid of the egr and knock sensor,better flowing intake and exhaust manifolds,bigger throttle body opening,and all the control points like flexplate,distibutor,tps,iac. Just strip your 91 block and the 88 and put your 91 stuff on the 88,but like I said if you can put the head from your 91 on the 88 i would do so,it is a beter head. If you do have someone inspect the 91 head.

 

Ok so I pulled the motor back out and changed the flexplate but I feel im running into another problem. I cant turn the motor from the crank at all well the fear of breaking it off sets in and i back off. But if i use a big flat head screw driver i can put it on one of the teeth of the plate and turn the crank well little by little of course just bu prying off of one of the dowl pins. so what does that mean? Im at a lose and dont know what the deal with it is. Do you guys know anything that might help out. O I put the starter on and tried bumping it and nothing weird Im so lose and frustrated.

 

have someone use a breaker bar or large ratchet and turn it over on the balancer,it is very hard to do it the way you are trying,also it will help to pull the plugs.
Do not get frustrated trying to turn the motor over at the flexplate is very hard,I think the bolt on the balancer is 5/8.

 

I tried from the balancer bolt and nothing it just gets to the point i feel im ganna snap it. i even tried putting 2 bolts through the holes on it to spin the balancer and nothing. but when i put my screwdriver on the teeth og the flexplate and used the dowl pin for leverage it moved it a little. i can move it that way but not from the balancer. thats why im at a loss on what it can be.

 

but you said you could turn it over with the starter correct? if you can then all is well,just make sure you have the studs from the torgue conveter through the flexplate. Did you remove the plugs,this will make it alot easier to turn. If you use your starter just bump it slightly.

 

I did remove to spark plugs. I just stopped for the day to clear my head about it and im going to make sure my battery is charged. I only got 1 bolt in the converter because i need to turn it to get the rest in. Im going to look at it all again in the morning and start all over and hopefully it works. Ill let you know tomorrow. Thanks again.

 

OK it is all coming along better now. I got her to spin over and got all the flexplate bolts in to the converter. I know the motor was tight due to just rebuilt it completely but hooking it up better with the starter got her to move. So Im not so stressed. lol