[Monster4570]

Recently brought this home for my wife.
Picking her up...

Happily at her new home...

5.8/E4OD Not sure t-case What was available in '94? (press down to enter N, I think it's a BW1356)
Runs great, no rust, very happy. Traded my bike for it. Worth about 3k.

She does have some small issues though. (Bronco, not wife)

There is a soft thump when taking off from a stop, switching from rev-fwd, and sometimes when shifting, I suspect a tranny/t-case mount.

Also RPMs bounce around a little, 100-150RPM by the tach and I can hear that the actual RPM is following suit. TPS maybe?

And thirdly, it takes forever to engage/disengage 4WD. T-case lever moves easily but I have to drive roughly 1/4 mile in town (snowy roads now) before she actually engages. Similarly difficult to disengage. Even after backing 200 feet. Any thoughts?

 

[Kenny's 94]

The thump, is probably your slip yoke in the rear drive shaft needs to be greased. Ford sells Teflon grease for the slip yokes it works very well.
If you have auto lock hubs that's probably your problem. Buy a good set of manual hubs. Warn Premium, or Mile marker hubs.
Looks like a nice Bronco.
Kenny

 

[Steve83]

All '87-96 use the BW1356, but the shifter on yours is the most delicate. Don't manhandle it or it'll break, and AFAIK, they're not available any more. They're getting scarce in JYs.

.

There's only 1 mount for the trans & t-case, but they rarely fail, and when they do, it takes a lot for you to notice. The engine mounts fail far more often, but they're VERY noticeable, especially during a WOT shift. Your description sounds more like a u-joint, radius arm bushing, leaf spring bushing, U-bolt, or pinion nut. But look under the seats for loose objects that could be rolling/sliding & making the soft thunk. It could also be this:



For the jumpy tach: how many large hoses connect to your air filter cover: 1 or 2? Read these captions:

. . .

What do you mean about 4WD engagement? Are you talking about the lights on the dash? How exactly are you determining when it's engaged or not?

 

[GetBent4x4]

Your t-case is probably thinking about that night in Memphis, but it's still stuck in Mississippi. Change the t-case fluid out to some mercon v synthetic. The drain plugs use a 10mm pipe plug socket, not a 3/8ths extension. Spray the shifter linkage with some pb blaster.

 

[Steve83]

Should've spent some time on Austin St. to ward off the DTs.

 

[hizootiemizark]

I had that same thump when starting from stop for years until I greased the slip yoke. It starts smooth as glass now. Do a search theres a great write up on here with pics. Easy job.

 

[Monster4570]

All '87-96 use the BW1356, but the shifter on yours is the most delicate. Don't manhandle it or it'll break, and AFAIK, they're not available any more. They're getting scarce in JYs.
Thanx, was not aware of the sensitive shifter.

There's only 1 mount for the trans & t-case, but they rarely fail, and when they do, it takes a lot for you to notice. The engine mounts fail far more often, but they're VERY noticeable, especially during a WOT shift. Your description sounds more like a u-joint, radius arm bushing, leaf spring bushing, U-bolt, or pinion nut. But look under the seats for loose objects that could be rolling/sliding & making the soft thunk. It could also be this:
Lube of slip joint and inspection of all drivetrain joints/bushings ensues.

For the jumpy tach: how many large hoses connect to your air filter cover: 1 or 2? Read these captions:
Two big hoses go to the throttle body. I have a fuel pressure gauge and will conduct this test soon.



What do you mean about 4WD engagement? Are you talking about the lights on the dash? How exactly are you determining when it's engaged or not?
Snowy roads here now, so it's easy to tell if the front wheels are engaged. When I move the lever to 4Hi the dash indicator illuminates instantly and I can hear the slight change in tone from the t-case so I think all is well there. But it takes some time for the wheels to actually engage and a similar lengthy period to disengage. When I push the t-case lever back to 2WD the dash indicator goes out instantly, but the wheels stay engaged. Front wheel engagement determined by making a tight turn or goosing the throttle.

Thanx for the input, I am not familiar with these hubs (5 screw autos) could they just need servicing?

Regarding 4WD engagement: For example, if I'm driving along and encounter a slick road surface, back end gets squirrly so I grab the lever but it takes forever to get power to the front end.

 

[Steve83]

Two big hoses go to the throttle body.

Wrong end - tell us about the AIR FILTER COVER end: 1 or 2? All these trucks have 2 at the TB end.

When I push the t-case lever back to 2WD the dash indicator goes out instantly, but the wheels stay engaged.

That's correct - auto hub locks don't unlock until you reverse direction.

Front wheel engagement determined by making a tight turn or goosing the throttle.

Depending on the type & condition of your front diff, that might only indicate that ONE lock is engaged.

I am not familiar with these hubs (5 screw autos)

Study the pics & diagrams in my Brakes & Hubs album, linked to my black Bronco in my signature. Everything related to 5-screw locks is grouped near the top of that album.

could they just need servicing?

Have you ever serviced them? If not... :thumbup

I grab the lever but it takes forever to get power to the front end.

That's not very conclusive. Put the t-case in 2H, put the trans in P or 1st (stick), crawl under, and try to rotate the front d'shaft by hand. It will take some grip & effort. If both hub locks are working, the d'shaft will only make a few revs before both locks engage & stop it. If either doesn't lock, the d'shaft will continue to spin, and you'll see the u-joint inside the steering knuckle of the bad hub lock rotating. Once a hub locks, it shouldn't unlock until the tire rolls relative to the spindle/knuckle the OTHER direction from what the axleshaft was doing to lock it.

 

[Monster4570]

Update-

4WD is working fine now. I cleaned & lubed the hubs. They now engage almost instantly and disengage with a short trip backwards.

I removed & lubed the slipjoint and the start/stop clunk is reduced by 90%. Barely noticeable now. I will follow up on this further after steelhead season closes. (2 days)

The air filter box has two hoses that run to the intake.


Haven't checked fuel pressure yet. (too many fish in the river) I'll get to that soon.

 

[Steve83]

cleaned & lubed the hubs. They now engage almost instantly and disengage with a short trip backwards.

It's amazing how effective & dependable auto hub locks can be when they get simple maintenance! :thumbup

The air filter box has two hoses that run to the intake.

So it's MAP/speed-density; not MAF.

 

[Monster4570]

Steve83, since my last post I ran across your outstanding PSOM thread.
The speedo in the '94 is 10-12% off. (67mph @ the needle= 60mph GPS) I figured there had been an adjustment for larger tires and would address the issue in time.

However the simplicity of the procedure indicated in your PSOM thread motivated me to deal with it now. But before I actually make any changes I want to get your opinion on my findings and a seeming anomaly in the current condition of the PSOM.

Rear axle is H9 (8.8" 3.55 LS w/108 tooth exciter ring), original tire size was 235/75 R15
I held RESET & turned key to RUN. Display was: E 08 6.
Press RESET again, display was: 851 CAL.

Current tire size is 32x11.05 R15. I used 30" as rolling diameter for the calculation.
(63360/(30x3.14))x108/8000=9.08 Conversion Constant I need

Here is the funny part though, my tires are LARGER than stock, but the speedo reads FAST! This would suggest that there has been an adjustment for larger tires at some point, right? But the first display still says E 08 6. Six changes remaining, right?
Am I not seeing something here?

Perhaps gear ratios were changed...hmmm...
The vehicle does show signs of a lift in it's past.
The radius arm brackets are bolted to the frame and the bumper is spaced about an inch forward.
That combined with the speedo error and the big fender flares makes me think somebody had a lift & larger tires at some point in the past.

 

[Steve83]

...I ran across your outstanding PSOM thread. ... Perhaps gear ratios were changed...

You should read it one more time... Gears have NO effect on a PSOM. I'm not sure how up-to-date that thread is - my most recent revisions & links to other resources are in the caption of this pic:

...original tire size was 235/75 R15
I held RESET & turned key to RUN. Display was: E 08 6.
Press RESET again, display was: 851 CAL.

Those numbers suggest the PSOM has been swapped from a much-larger truck, like an F550 or something with BIG factory tires. That constant (8.51) wasn't used on any light truck, according to these charts:

And 6 lockouts means the constant hasn't been changed by the published procedure. There are marginally-legal services that will "repair" an odometer (usually for a used car lot), and they MAY be able to change the constant without decreasing the lockout count.

Current tire size is 32x11.05 R15. I used 30" as rolling diameter...

That's not good enough. The PSOM is much more precise than that. You need to find the published RevsPerMile for your particular tire brand/model/size.

...my tires are LARGER than stock, but the speedo reads FAST! This would suggest that there has been an adjustment for larger tires at some point, right? But the first display still says E 08 6. Six changes remaining, right?
Am I not seeing something here?

You saw it, but didn't notice: the 8.51 constant is for an even-bigger tire, so yours are SMALLER than what the PSOM is programmed for, which makes it perfectly understandable that it shows fast.

 

[Monster4570]

You should read it one more time... Gears have NO effect on a PSOM.

No, I got it the first time. Thanks.

Gears DO, however have an effect on the speedometer reading vs actual speed.

Consider the fact that my PSOM shows six changes remaining and that there are larger than stock tires. It is a perfectly logical conclusion to the layman that the Conversion Constant had not been changed and the gear ratio had been changed to suit the larger tires.

Also a reasonable conclusion that the conversion constant had been changed without altering the lockout count, or that the PSOM came from a larger vehicle.


However, considering the fact that the conversion constant equation, when worked backwards yields data indicative of a 34"-35" tire, I consider the most likely scenario to be that someone found a way to hack the PSOM and leave the lockout count at six after adjusting the conversion constant.

But this is all speculation anyway and has little effect on my current situation other than to satisfy my curiosity.

That's not good enough. The PSOM is much more precise than that. You need to find the published RevsPerMile for your particular tire brand/model/size.

Since neither the manufacturer or Tirerack list my tires specs I have noted the specs of several similar tires and performed calculations using a measured rolling radius, comparing my results to the published data to establish a margin of error for my method and will proceed to apply this method to the tires in question. (Wild Country TXR 32x11.50 R15) I will post results here later.

 

[Steve83]

No, I got it the first time. Thanks.
Gears DO, however have an effect on the speedometer reading vs actual speed.

Apparently, you don't get it. Gears do NOT affect a PSOM's accuracy in any way. If the PSOM is calibrated to the tires, and you only change gear ratio, the PSOM will remain calibrated - exactly as accurate as it was before the gear change.

Gears affect every OTHER kind of speedo on Ford trucks, but not a PSOM. :thumbup

It is a perfectly logical conclusion to the layman that the Conversion Constant had not been changed and the gear ratio had been changed to suit the larger tires.

If the layman lays under the truck & examines the axle tag (and AXLE code on the door jamb sticker), then pulls either the fill plug or ABS sensor & rotates the d'shaft (front tires chocked, e-brake OFF, trans or t-case in N, at least 1 rear tire off the ground) until the gear ratio is visible on the edge of the ring gear, he'll know if the gears have been changed.

Since neither the manufacturer or Tirerack list my tires specs...

Put a HEAVY chalk mark (use powder for a carpenter's chalkline) on a tire, drive straight forward on clean flat pavement until the chalk comes back to the top, add a little more chalk, and drive forward again so you have 2 good marks on the pavement. Measure inches between them (roughly 120-144") and back-calculate your actual RevsPerMile.

(1Rev/???Inch) x (63360Inch/Mile) = (63360/???) = XXXRevsPerMile

 

[Monster4570]

Apparently, you don't get it. Gears do NOT affect a PSOM's accuracy in any way. If the PSOM is calibrated to the tires, and you only change gear ratio, the PSOM will remain calibrated - exactly as accurate as it was before the gear change.

Investing further thought on the matter...

I suppose the exciter ring must revolve in conjunction with the carrier. Therefor any change in the gearing would be detected by the PSOM. The result would be increased/decreased engine RPM at any given speed, but the PSOM would still detect carrier speed (and therefor wheelspeed) correctly.



The only change the PSOM cannot detect would be...tire size...

I think I get it now.

 

[Monster4570]

Worked perfectly, took about two minutes.
Speedo is now within 1-2% of GPS.

Thanks Steve83!