FMTV questions

[Retiredwarhorses]

Just picked up a 1078 on a trade...couple of questions

diffs, I assume is 80-90 GO, it's a little noisy up front and read a thread about checking levels...other then the main diff housing, where else is it checked?
I see no other access point...unless I'm mistaken.

on the trans bell housing , there is an access panal...mine is missing, held on by 4 bolts...Or is this normal to be not installed?

does tcase take 80-90 GO

what is used in trans? Looks like 15-w40 like the m939 I have.

speedo jumps around...where does the cable terminate into the tcase?

lastly....what are your speeds? I can't get this truck to go over 50mph...and all
the while the CTIS over speed flashes...regardless of speed.
ctis is set to highway.


runs very well all in all...

 

[Suprman]

It has planetary hubs each hub gas its own reservoir. There are plugs on the hub ends. Something I recently learned myself. Trans and transfer case are mated and share fluid. I think it's regular oil same as the engine. Speedo is electric if its jumpy and the trans shifts incorrect then the speed sensor under the trans needs replacing. It's an otc allison part. It should do 57. Replace the speed sensor it's prob making the ctis overspeed light come on. The trans ecu and ctis share speed info.

 

[Retiredwarhorses]

Is that the 8 pin connector on the front of the tcase?
Im trying to down load the TM's but having bandwidth issues...

I see the Allen head for the front hubs...what's the procedure on those, meaning...what's the plug orientation when checking? And how much to fill?

 

[Lmtv772]

Is that the 8 pin connector on the front of the tcase?
Im trying to down load the TM's but having bandwidth issues...

I see the Allen head for the front hubs...what's the procedure on those, meaning...what's the plug orientation when checking? And how much to fill?

Checking the planetary gear set is in the 4o'clock position on a level surface. Front should be a tad bit under the threads. Fill with 75-90 GO. Check the diffs do the same here.
rear check if fluid is present, if overfilled put plug back and check diff fluid level in the rear diff..

 

[Suprman]

Back of the trans is the speed sensor. It's called different things in different manuals. Transducer motional #8

 

[Retiredwarhorses]

Looks like a TISS or TOSS...on hmmwv thy get gummed up and just need cleaning...will pull it out in the AM.
thank you sir..

 

[Retiredwarhorses]

Checking the planetary gear set is in the 4o'clock position on a level surface. Front should be a tad bit under the threads. Fill with 75-90 GO. Check the diffs do the same here.
rear check if fluid is present, if overfilled put plug back and check diff fluid level in the rear diff..

so the rears should be dry? And if wet, that means the diff is overfill?

 

[Suprman]

The sender is a magnetic pickup I believe. I tried cleaning on before it may work better but not right. The trans ecu is dependent on that sender. You won't have proper shifts till a new one is installed.

 

[Retiredwarhorses]

Checking the planetary gear set is in the 4o'clock position on a level surface. Front should be a tad bit under the threads. Fill with 75-90 GO. Check the diffs do the same here.
rear check if fluid is present, if overfilled put plug back and check diff fluid level in the rear diff..

i printed the Lube order, why does it not have the fluid type for diffs listed but everything else?

 

[Retiredwarhorses]

Checking the planetary gear set is in the 4o'clock position on a level surface. Front should be a tad bit under the threads. Fill with 75-90 GO. Check the diffs do the same here.
rear check if fluid is present, if overfilled put plug back and check diff fluid level in the rear diff..

all I have is 80-90....should this suffice?

 

[Lmtv772]

I can't vouch for it. I made sure its 75-90. But to answer your question about the rear hubs. they are supposed to be filled, but in my trucks for instance the rear hub would drain as much as 5 qt straight from the differential. Therefore I just check for fluid and if there is fluid in the hubs , I check the rear diff for proper level. I won't drain the rear hubs if there is too much inside. just the front.

 

[TNriverjet]

That sounds correct as the rear is a full floating axle setup and fluid from the rear diff can flow out to the bearings at the hubs. I believe filling properly at the rear diff plug is correct lubrication for hubs. The LO addresses this by calling out one lube for the rear and has separate designations for the front diff and hubs. Though it is the same fluid for each, it still addresses separately due to the separate fill locations.

 

[sargentwolf]

If you changing fluids, change the transmission fluid over to heavy truck/tractor ATF. It shifts MUCH smoother vs motor oil. There's a great thread on here about doing it.

Also service the air dryer.

Far as the CTIS goes, try reseting it. How to is in the manual, I've never done it but heard it fixes most of the problems. Or just unhook the box entirely, long as you remember to fill and check it should be ok.