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Discussion Starter · #1 ·
So here's the skinny on this transmission.

I bought this truck 12,000 miles ago used from a guy up in Boiling Springs. Its served me well over the past year (sans replacing a slave cylinder) but I had always noticed a grinding when going into fifth gear, even with the clutch depressed, if I did not go from 4th to 5th at proper RPM's.

For the last month I have been living in downtown Charleston where there is no need to go past 3rd gear, as most of the roads are too narrow. So it had about of a month of rest where 5th saw no action what so ever.

When I finally got it out on the highway though it just wouldn't go in to fifth. I can push as hard as I want and all over the RPM spectrum but it just doesn't work. Double clutching had similar results.

I changed the oil in the transmission 5,000 miles ago. It looked very clean and as far as I can tell it was changed before that (as was evidenced by a stripped transfer fill plug). I replaced it with 15w-40 conventional motor oil.

Any thoughts? The only threads I've seen on this include a situation where someone can neither reverse or go into fifth. Something to do with the shifter but this is 5th gear only.

Any help is much appreciated.
 

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Discussion Starter · #3 ·
I chose the 15w40 because its so hot down here. I thought it may be a good a oil to use in 90-100 degree temperatures but I am definitely going to change it out before winter. It did shift fine with 15w-40 for eight months though.

About float shifting. I actually tried pushing it over the entire RPM spectrum to see if it would slide in but nothing happened. All the evidence leads to the synchronizer being burnt out but I'm really hoping its more of a simple fix.

Thanks for replying.
 

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5th gear sometimes hangs over the rear support bearing, making it easier to replace than the others. However I am not 100% sure this is the case with the Isuzu and being an MUA5 you need to deal with the integrated transfer case which makes is harder that a normal 5 speed.
 

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You might want to talk to Jerry Lemond.... he has a new MUA5 Isuzu transmission with the attached transfer case.

For the price, it might be worth it for you.. just sayin'
 

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Discussion Starter · #6 ·
If I have to completely drop the transmission I may need to wait for the right time, as I'm guessing this isn't a project a bumbling noob could hand;e over a weekend. I might have to just drive it as a four speed for a week or two.

I suppose I'll see if I can find a rebuild thread when I get the money to do so. Looks like the clutch is on its way out too so I might as well tackle them together.

Thanks for the replies guys.
 

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If you can find one at a local salvage yard it may be worth it to pull one from there and swap in. The MAU-5 is pretty tough so I wouldnt worry about any issues with a used one. The local pull and pay yard here charges $100 + $20 core charge for a trans. The yards here usually have several 1st gens and often have '96-97.

If you just swap a trans you can drop the old, replace the clutch, and install the new one in a day. We did a clutch in the campground in Moab in a day.
 

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How sloppy is the shifter? Does it wobble left-right / up-down?

The little plastic nylon 'cup' on the end of the shifter rod - inside the shifter tower - sometimes breaks and falls into the space that you need to enter to get into 5th gear.

If you take the shifter boot off, you'll see 4 little 10MM headed screws that you can remove and inspect the end of the shift shaft.

Nothing will fly out or get lost - just pay attention to what you see.
 

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Discussion Starter · #9 ·
I was actually able to get it into 5th today after a 60 mile drive at 3000 RPM. It really took some finagling and some muscle but I was able to work it in. No crunch or anything. I tried my hardest last night but couldn't get it to go in, no matter what position or what RPM range. At least I know its no internal.

And yes the shifter is very sloppy. When I get done with these awful summer classes and have my tools back I'll remove the shift boot and see whats in there. I'll try to get some pics.

Could this be an issue with oil viscosity? I really didn't think that 15w-40 would have been that bad. Its listed on the owners manual after all. The only reason I say that is because it finally went in after a really long drive at relatively high cruising RPM.

All advice has been much appreciated.
 

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Not oil viscosity as far as I can tell - just age and brittle plastic.

I'd not force it too much as those pieces are gonna get into the transmission and MIGHT foul some stuff up - a little or a lot.

Besides, the plastic is still crunched up in there and although you THINK you are really all the way in 5th gear, you may not be - and that can seriously damage the slider and possible the teeth on the blocker ring if it pops out under power.

I say check it out ASAP!

I don't know if Jerry has those plastic swivel ends available - I built a replacement out of a piece of brass I machined and put on the end of what you will find is a small ball on the other/inner end of the shift shaft. I have NO slop in the shifter at all.

CLICK-CLICK-CLICK, gear to gear.
 

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Discussion Starter · #11 ·
I had no idea it could be that serious. If I have some time after class tomorrow I may go ahead and check it out.

In any case thanks for the warning. This is going to be my only ride for a while and I can't afford to screw anything up. I'll try to post some pictures after I get out of class.
 

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Any time something has to be forced to make it work - unless we are talking about brothers-in-law who live with you - it's not a good thing.

I went back in the 'Way Back Machine here on the site and pulled up what is NOT the correct picture - not like what I have in my Isuzu - but you can get the idea anyway where you're gonna have to go.



BTW: that little part - albeit the wrong one - is labeled NSS which means you can't buy it separately.

I also succinctly remember that it's a four-bolt cover, not a two-bolt as depicted in that pix.

When you get your shifter boot off, it'll be obvious I think, as my Isuzu has a shifter tower that places the gear shift further back from where that one is mounted. Confused? Me too.

Still - that's not the right part, although generically, it's sortta in the right position.

EDIT:::

OK - more research (where's Jerry????)

I found a shifter that is exactly like the one in my Isuzu - the ball end and all - if you don't pay attention to the other Suzuki parts, that is:::



Look at the end of the shifter itself and see the tiny ball end on it? That's where the plastic piece pops over - and if you squint, you can see the little plastic part too down low in the isometric drawing there.

JERRY --- YOU ANYWHERE NEAR HERE????

OK - I hit on another picture on Google'n around:::



It ain't Isuzu, but it should make the mental pix easier to fathom.

EDIT EDIT EDIT EDIT EDIT

I FOUND MY PICTURE - I FOUND MY PICTURE!!!!

This is the part that was snuffed in my Isuzu:::

 

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Discussion Starter · #13 ·
Okay, I've been bored studying chemistry so I went outside and yanked the shifter out and all the plastic cup seems fine. Sorry about the lack of pictures but my computer won't accept my phones software without some type of CD.

The cup was made of some pretty thick plastic and showed no signs of wear, let alone failure. The other two or three times I needed to put it in fifth driving into town it seemed to go fairly smoothly. But problems rarely fix themselves. I just don't get it.
 

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Ya gotta find that slop!

It's in there and there's a broken part that's messing with you - keeping your 5th gear rail from moving forward.

Hopefully, we is talking the same parts here - but that side-to-side and other wiggle is a tip-off.
 

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Look inside where the plastic cup sits - do you see the shifter rails or not?

Through all sorts of monkey motion, the plastic cup moves another finger that selects and moves the rails.

You might try to shift the rails with a fairly heavy screwdriver to see if the all move fore and aft.

The 5th gear is on the same rail as the Reverse gear.
 

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Discussion Starter · #16 ·
I just took another look inside and all I can see is the shifter linkage. Where the little ball on the end slips into. If it helps anymore, I stuck the shifter back in (unconnected) and it still won't go into fifth.
 

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Discussion Starter · #17 ·
Alright just got back in. I messed around with the linkage with a screw driver, got it back into a place that the shifter would fit in and inserted it unattached. It goes into reverse and I was able to get it to go forward in fifth.

Unless I accidentally set something right playing around with it, there doesn't seem to be a problem anymore. I don't get how something could work itself out this way. I'll go on a test run tomorrow and if it gives me anymore sass I'll keep you updated.

Thanks for sticking with me guys.
 

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Is your shifter on another casting that sets the whole shifting mechanism closer to the driver's hand?

The shifter rails are gonna be in there. You may have to take that whole top tower assembly off to see what's going on.

I bet one of the blocker dogs is messed up or a parallel shift rail blocker pin is screwed up.

They usually have a system where only ONE shifter rail can move at a time and all must be in neutral position for any of them to move from that position.

Simple - huh!

But you gots to try to manually move that REV/5TH rail with a big screwdriver to see if the resistance is in it or further down into the unit.

The slop in the exposed shifter bothers me yet though. You should be looking hard for that - and remember that a tiny bit of slop in the tower creates a LOT of slop at the knob end in your hand.
 

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Discussion Starter · #19 ·
Then it sounds like I have a bit more digging to do. I have two more chapters to read before I go to bed so this might have to hold off for a bit.

But I think I will have to take off the top. I borrowed a flashlight from my roomate and looked down there. The only thing I could see was the reciever for the little ball that slipped into the yoke.

When I get home Thursday I'll be able to borrow a camera and take some pictures of whats going on down there. I just wish there was more time earlier this week. I have two exams coming up and summer classes have not been kind to me.

If theres a problem I would just like to nab it before something else screws up.
 

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That extension housing is prolly where you'll find the trouble.

It could even be a broken retractor spring or something stupidly simple to fix.

The slop will lead you to the problem.

I do NOT remember if there are roll pins in the shifter rails to the detent area or not. I'm old.

Every manufacturer tried THEIR way to save a buck - and it's not possible to remember all the vast configurations I've worked on - but physical law and monkey motion can be diagnosed and repaired by a human.
 
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