Full Size Ford Bronco Forum banner

1 - 12 of 12 Posts

·
Registered
Joined
·
145 Posts
Discussion Starter #1
Hi all,
I have a 95 Bronco with E4OD trans and it has developed an issue Shifting. I have never experienced this before nor could I find any info about it. My trans shifts from 1st to 2nd then 3rd in a matter of seconds on takeoff. It will come back to 1st and do it all over again and again. I can shift to 1st manually and it will stay there but as soon as i go back to drive it starts all over. I have pulled codes and all i got was a 633 but not sure how to attack the problem. Anyone else ever experience this or any ideas on what to do?

Thanks
Scott
 

·
Premium Member
Joined
·
999 Posts
Are you running stock sized tires?

If you are not, then watch this thread and verify you have the correct setting in your PSOM. If you PSOM is not set correctly, all kinds of weird stuff happens. The signal coming from the VSS says you are traveling at a certain speed, but in fact you are traveling at a different speed. The reading is skewed because of the circumference of your tires has changed if you are running bigger tires.

Watch this video to understand how to check and then reset your PSOM.

I had similar problems where my newly rebuilt transmission would just suddenly go into neutral for not reason. I had changed my tire size to 35's up from 33's and that two inch difference in tire size really screwed up my PSOM. Once I watched this video and reset the PSOM, all of my problems went away.

This is a free and easy thing to check. If your problem goes away, then all is good. If not, you have lost nothing.


( insert 2 cents emoji here )
 

·
Registered
Joined
·
145 Posts
Discussion Starter #3
I am running 35's but I have also re-geared to 4.56. I know this doesn't get it back to the stock setting but it should be close. I will do some figuring and try this and see what happens. Thanks for the help!
 

·
Premium Member
Joined
·
1,913 Posts
You could also try pulling the PCM and opening it up to check for damage. I know its common for the resisters in these old control modules to fail and cause problems with controlling the transmission shifting.
 

·
Registered
Joined
·
145 Posts
Discussion Starter #5
My PCM does have blown resistors and I have a new one ready to go in but I want to make sure I don't have an issue before I install it and end up burning up the new one.
 

·
Premium Member
Joined
·
999 Posts
My PCM does have blown resistors and I have a new one ready to go in but I want to make sure I don't have an issue before I install it and end up burning up the new one.
Umm, the blown resistors are your issue..... they normally blow because of age, not power surges.

I would put the new PCM in now and verify your PSOM settings. I bet you will be golden after that...

Always fix what you know is wrong / broken first before trouble shooting. It will save you a lot of grief....
 

·
Registered
Joined
·
145 Posts
Discussion Starter #7
Ok, I understand how to do the PSOM for taller tires but I couldn't find anything on how to do it for tires and a gear change. Can someone explain or shoot me a link that will explain.

Thanks
 

·
Super Moderator
Joined
·
23,327 Posts
Yo Scott,
As klh95bronco advised.

The 92-96 Bronco & F Series Programmable Speedometer Odometer Module (PSOM) obtains information from an exciter ring next to the ring gear in the rear differential. Because the ring gear (and the excitor ring) turns at basically the same speed as the tire regardless of the rear end ratio, the speedometer only needs to be recalibrated to account for changes in tire size.

633 in koeo is 4WD switch is closed ot.
4x4 low switch closed/or 4x4 low indicator lamp circuit open.​
Failed on - Early shift schedules in 4x2 and 4x4 HI range.
Failed off - Shifts delayed in 4x4 low.
NOTE: If the 4x4 low indicator light fuse is blown, the transmission will shift according to the 4x4 low shift schedule regardless of the transfer case position.​
 

·
Registered
Joined
·
145 Posts
Discussion Starter #9
Thanks for the help guys! I'm going to jump on it tomorrow and see what I can come up with. I will let everyone know what I find out. I have some other things to fix so hopefully I will have it back on the road by the end of the week.
 

·
Registered
Joined
·
145 Posts
Discussion Starter #10
I checked my PSOM on my 96 F150 this morning and it is set at 972. I am running 31/10.50x15 with 680 revs per mile. My figuring got me a PSOM setting of 918. I wanted to verify this is correct before I make any changes, my math isn't that good. I will check the Bronco this evening.

Thanks
 

·
Premium Member
Joined
·
999 Posts
I checked my PSOM on my 96 F150 this morning and it is set at 972. I am running 31/10.50x15 with 680 revs per mile. My figuring got me a PSOM setting of 918. I wanted to verify this is correct before I make any changes, my math isn't that good. I will check the Bronco this evening.

Thanks
Based on the numbers you have above I calculated the conversion constant and I also came up with 918.

Before you do any other work on your truck I would change the setting on the PSOM and drive it for a few days. With a difference in the setting that large, I am betting this may very well be your problem. I hope it is for your sake, it is an easy fix...

Change it and then after a few days update us on your results.

Don't forget to reset your PCM. Take the battery cables off and let it sit for a good ten minutes then put the cables back on. This resets your computer and it will boot up not expecting the problems you had earlier.
 

·
Registered
Joined
·
145 Posts
Discussion Starter #12
Thanks for double checking my math. I'm not going to mess with anything else other than brakes, shocks and rear window not going all the way down. I will change the PSOM and see what happens before trying anything else.
 
1 - 12 of 12 Posts
Top