No Reverse

So I was driving my truck around on some dirt roads. Nothing to extreme. Now when I put the truck in reverse nothing happens. The engine revs as if it were in neutral. Should I start looking for a new transmission?

In any forward gear the truck moves no problem.

 

automatic, you got a problem, maybe the linkage got disturbed offroading...otherwise, your tranny may have gone fubar..

 

Have seen issues with the transfer case causing no reverse .
What happens when you select 4X4 and 4Lo ?

Did you get the truck stuck ? and does the truck still have low gear ?
the same clutch pack used for reverse is also used for forward -Low gear .
The truck starts in park but will it start in neutral ? this may rule out a linkage issue .
The transmission uses very high pressure to get reverse . Are you sure its topped up with trans fluid ?

 

^^^Sounds like good tranny advice from a guy who's username is 'Gearcruncher' lol

 

Update. All that works is first gear. If I put the truck in "D" it will only use first gear. Only when I put the truck to "2" will it seem to upshift, but it just seems like it shifts to neutral.

 

have you checked the fluids, climbed under to give a visual inspection, how is the fluid level?

Maybe a transmission shop can render an opinion at this point...

 

Checked fluids, looks bright red, doesn't smell burnt. I looked through the FSM I found online but I can't find anything that would cause a symptom of no reverse.

 

Reverse inside the A750E is strictly mechanical . This means there are no solenoids or computer controls used for the transmission to select reverse .
When you select reverse , the linkage moves the manual valve inside the valve body of the transmission and hydraulic pressure applies the clutching to get reverse . No ECM controls , no solenoids are used
Did you get the truck stuck ?
Have you tried the transfer case in 4X4 and 4 low ?
Will the truck start in park and neutral ?

I am going with broken planetaries if the above is tested and all works fine .The same planetaries used for reverse are also used for upshifting in the forward gear ranges . Portions of the valve body could be jammed up but usually there is a cause for the spool valves getting stuck .
If the ECM commands the transmission to upshift to 3rd gear but for some reason or another , it doesnt upshift , the ECM will put the transmission into fail safe to prevent further damage but even if the transmission was in fail safe , you would still get reverse .
Sounds like you are now in fail safe mode .

 

Doesn't that trans also apply direct clutch pack in reverse? Never had one apart but doesn't it also have a sprage on the low clutch drum? It sounds like he broke some thing not a normal worn part type of thing.

 

Havnt looked at the actual powerflow , but I beleive you are correct

 

So I dropped the truck off at a transmission shop this morning. I'll update as soon as i hear back as to what failed.

I wish it broke in the summer so I could have time to swap the transmission myself, I just don't have the time during the school year. (MNE Senior)

 

Just got a call from the shop. The truck will only shift into first and fourth. Hopefully it is a solenoid issue. But if reverse is strictly mechanical i guess there is more wrong. Next call will hopefully be in the afternoon tomorrow.

 

No it not mechanical but it has no management to it (computer control) It still has to apply clutch packs with trans fluid.

 

Just to have the problem listed in this page, I broke a planetary ring gear so i am getting it rebuilt.

 

Could you take a picture of the broken part ?
Did they say why it broke ?

 

They asked me if i jammed it into gear while the truck was rolling. i.e. rolling back and putting it into drive or rolling forward and putting it into reverse.

I swear i didn't do anything like that. It just stopped working, no bang, no grinding, nothing. I even continued driving long enough to get out of the trails to get towed, and there wasn't any grinding sounds. At the time i was convinced it was an electrical problem because i had been through some puddles.

I asked them to keep the broken parts. When i get it back next week I will get more specifics on which part failed, and ill post pictures.

 

I have seen the ring gear break off the lower planetary carrier many times in the past but not on the A750E . The ring gear is welded on the planetary in multiple locations and the welds break . If this is what happened , its not something you did . Poor welding , poor machining , incorrectly baked when the transmission was being built or 99 % of the time , this is caused by not coming to a complete stop before moving the manual linkage to forward . Selecting reverse under high engine rpm would also break the planetary
Have you owned the truck since new ? could be something that happened previous to you owning therefore it was a matter of time .
This is a rare occurance and not a pattern failure for the A750E.
Be happy we dont own a Ford or Chevy . Broken planetaries and busted gearing are very very common on their automatics to the point that they are designed to fail .

 

Crap, so in a parking lot I stopped, kicked into reverse and nada- rev'ed like nutural- did a sanity check, went into park, back in reverse, free reving. Put it into drive and the tranny kind of spurtered into forward motion. Lately I've noticed some 'spurtering' like 1st gear instances, this reverse issue (I have not been able to reproduce) is new. Context 2001 4x4 with 240,000 miles, original tranny (that I know of), Amsoil sythetic in the tranny, flushed about 40K ago. Due to the 1st gear intermintent issue (very very rare) I drained the pan's ~2 quarts and put in new fluid. The tranny shifts amazing outside of these issues. Time for a rebuild?

 

@gearcruncher
This dude knows what’s up.

 

Your transmission is a 4 speed automatic . This post deals with the 5 speed automatic in the second gen trucks .That being said , reverse is mechanical in both transmissions so i suppose the diagnostics are similar to what you have been reading above .
To eliminate the transfer case , try 4x4 low ..... if no reverse , its time for a rebuild or at minimum a reverse pressure test .