Dead MJ

[trippnk]

Okay, decided to go floating yesterday with friends and was volunteered to drive the truck to haul crap. Well after starting her up in the morning it was shifting really funny. Like from a stop it would rev up and then drop into gear and it would rev and slip in and out of gear just going down the road. After about 5 miles of this the dumb thing died while going down the road. I had to coast it to a stop on the side of the road were it was dead. I tried to start it again but it would just crank, no fire. Left it there and moved everything to another truck. On the way back like 7 hours later I stopped and tried again but same problem, good cranking but no fire....... I did a little reading and it looks like it might be the CPS but I really don't know. Anyone got some advise???

 

Thanks, Kendal

[JeepcoMJ]

Okay, decided to go floating yesterday with friends and was volunteered to drive the truck to haul crap. Well after starting her up in the morning it was shifting really funny. Like from a stop it would rev up and then drop into gear and it would rev and slip in and out of gear just going down the road. After about 5 miles of this the dumb thing died while going down the road. I had to coast it to a stop on the side of the road were it was dead. I tried to start it again but it would just crank, no fire. Left it there and moved everything to another truck. On the way back like 7 hours later I stopped and tried again but same problem, good cranking but no fire....... I did a little reading and it looks like it might be the CPS but I really don't know. Anyone got some advise???

 

Thanks, Kendal

 

it's the CPS not reading. but that's symptom of a cracked flexplate (automatic flywheel if you will) if the tranny wasn't shifting. has it been making a clanking/clattering sound? . either way I feel you have one of two problems...cracked flywheel or your torque converter bolts hav sheared. of course, the torque converter bolts can't be it as your engine would still run if the flexplate was rotating. it's what the crankshaft position sensor gets it's timing reading off of.

 

a new one is about $80 shipped to bumper to bumper, but be sure that if you do need one, you get one for the same vintage of truck...a HO motor won't run off of a pre-90 flexplate and vice-versa.

[trippnk]

I think I understand but are you saying buy a new CPS or a new flywheel? The sensor is only $32 at Autozone. Also, I've never unbolted a tranny before, is it hard, do I need to drain anything before I do? Sorry for all the questions.

[Pete M]

Sorry for all the questions.

 

See rule #2. :D

http://comancheclub.com/forums/viewtopic.php?t=1239

[comancheman]

pull off the inspection cover on the bellhousing and look for anything abnormal on the flywheel. if u need to replace the flywheel u should drain the fluid from the tranny before u drop it.

 

i would replace the cps anyway before i dropped the tranny unless it was very evident that the flywheel needed replacing.

[JeepcoMJ]

if there was any excessive chatter/loud noises from the tranny before it stopped working, it's probably going to be the flexplate, but take off the inspection cover first and look @ the flywheel. also, replace the sensor as well before anything else....it's just 2 12mm bolts and one connector.

 

 

to drop the tranny you need to drain it, unbolt the inspection cover, the torque converter (4 bolts on the back of the flexplate), the CPS, starter, tranny dipstick tube (and another bolt directly opposite of that, then the two large side bolts for the bellhousing and the 6-point bolts on top.

 

 

of course, first you drain it and do the starter and front driveshaft and remove the dipstick tube (spray the joint that's in the middle of the tube with PB blaster) and use a flathead to pry on the tube mount via the bellhousing, as well as the tranny cooler lines, then unbolt the torque converter then drop the crossmember and remove it from the tranny, disconnect the wires to the tranny (right next to the top of the tranny dipstick tube). then all the bellhousing bolts and drop her down.

 

5 or 6 bolts hold the flexplate to the crankshaft.

 

whenever removing a auto trans, it's always pertinent to replace the front seal (torque converter seal) because it will go bad down the road, if not right away, and you'll kick yourself for not doing it then. it's easy to remove with a small screwdriver, and you can tap the new one in nicely with a small hammer going in a star pattern. it costs $4 or so.

[trippnk]

Thats a little overwhelming! I'll probably just check the sensor and if thats not it just have a shop fix it for me! LOL Oh.... would the CPS alone cause the tranny to shift screwy??

 

 

Sorry for saying sorry PETE!!! :D

[87manche]

Thats a little overwhelming! I'll probably just check the sensor and if thats not it just have a shop fix it for me! LOL Oh.... would the CPS alone cause the tranny to shift screwy??

 

 

Sorry for saying sorry PETE!!! :D

 

it's possible,

it may not have been the trans shifting funny, but misfiring in the motor because of the failing CPS.

 

You should also check the TPS.

The TPS input is important to the trans shifting, and a completely shorted part can keep the motor for starting, because the renix box will freak.

 

try disconnecting the TPS and cranking it, it should start with no TPS signal.

[trippnk]

Awsome, I'll give that a try too!

[trippnk]

Just to follow up, I replaced the CPS in about 15min and the Heep cranked without a problem. The Tranny slipping was due to a crack in the coolant line running to the radiator which was probably my fault. I think it cracked when I switched over to the open loop radiator which works great I might add. As soon as I get that leak fixed she should run like a champ!