Transmission slipping??? on CUCV

[OL AG '89]

I am sure this has been covered..... but when I go to back up the CUCV and try to get off dirt onto pavement.... about 3 - 4 inches difference, truck can't move itself when going from sitting still..... have to get a rolling start....

It runs fine tooling down the road, just seems to "slip" from a start not on level or even ground....
Its like it has a high stall speed converter in it, but it never gets enough power to move truck...

I haven't changed fluids or filter, I have checked fluid, color is fine, level is good......

Anybody got any suggestions?

 

[OL AG '89]

Anybody?

Have I stumped everyone????

Anybody have any suggestions for this?
I'm gonna pull the pan this weekend and change fluid and filter.....
Not sure what else to do .... other than trans rebuild..... not ready for that expense.....

Is this maybe a torque converter issue?

 

[Shop Rat Fab]

The key to diagnosing any trans concern is to first make sure there are no drivabilty concerns or a worn out engine.
It's your vehicle that I would assume you have been driving for awhile so you would know if it is operating differently than before. As for the 3-4 inch will not climp mine is the same way going up curps, I blame it on the high gear ratio (mathmatically lower) in the axles so I get a running start. Mine does not slip going down the road though. If the fluid looks burnt and smells burnt its most likely going to need a rebuild changing it will not fix the worn out clutched. If the fluid is okay the convertor could have taken a dump. You would need a tachomater in order to test the stall in the convertor or just brake torwque it and try to judge wheather or not its slipping.

 

[OL AG '89]

slipping or not?

PK,

My concern is that I get into the dirt, mud, or whatever and it has no power to get me through.....
The truck runs great, "pulls" good from a dead stop, doesn't "feel" like its slipping when driving along at speed.....but, it doesn't feel right as I try to go up a small "hump" from dirt to pavement....
my only real concern.......

The torque test is easy enough, but as I understand very "stressful" on the tranny....

maybe I'm worrying about nothing.........

 

[Shop Rat Fab]

With engine and trans at operating temp do your WOT stall test for no more than 5 seconds then the put the trans into NEUTRAL and run the engine at 1,000 rpm for about 15 seconds to allow the torque converter to cool off. Stall test stressful on the fluid and convertor as it gets hot fast. Are those 33s or 35s on the truck? Taller tires make a difference for sure. How is the truck in 4x4 low?.

 

[OL AG '89]

I went to check on a "trans flush" last night.....
I know, I know..... I have heard good and bad about the "flush" with a high mileage trans...... but I figured I'd see what it would cost.... HOLY COW!!!!! $170 and that does not include changing out filter or dropping trans pan....
I think I'll pass.
Went and picked up a filter do at least do that, with a fluid change....

The tires are 33's, I had thought about that, but realizing this thing has torque out the wazoo, didn't think much about it.

I have not yet put her in the dirt to really test out the 4x4...... Don't have a lot of dirt trails around Kingwood.......
maybe have to travel to the local 4x4 track this weekend.... will trailer to spot just in case......

Anybody have a trustworthy trans shop in the North Houston area????
that would be my next stop is to let them do a little check on the trans before I go thrash it in the dirt...

 

[OL AG '89]

Idid the filter replace and fluid change last night....
except for spilling have the pan across the driveway it was a piece of cake....
I noticed some "chunks" see picture in the bottom of the pan, not grease or dirt chunks but material chunks.......
I'm not sure what the clutches are made of, but I think I remember they looked similar to a cork gasket material, just denser....
Another item that was "troubling - interesting". The filter was hanging at an angle in the pan.... see the last picture It was not tight against the trans, rather just hanging from a bolt and spacer....
Is this correct? normal? approved? or FUBAR????
I procured a shorter bolt and fastened it to the trans gently....... dealing with aluminum threads....

Anyway, got it all back to together added the correct amount of fluid.... 4 quarts .... still a little low but didn't drive it to heat it up...

Seems to drive better at low speeds..... it climbed right over 4" curb..... that was the previous issue of not "powering" over curb from dead stop.....
Now want to add a trans temp gauge to see what kind of heat this thing is generating...
gonna rig something temporary just to see and then fab up a console for the rest of the "good to have" gauges.... oil press., oil temp., water temp.
Would like to put them in pod under dash... we'll see where I get with that project...

 

[Barrman]

I had the same thing loading mine on the trailer picking it up. no guts. I put it in low and it jumped right up. Mine wasn't slipping though. Am I reading yours wrong?

 

[OL AG '89]

Barrman,
I think the filter and fluid change helped, didn't get to take it out tonite had to work late then helping my son with his 74 Blazer..... I'm gonna give it good drivin this weekend, maybe down to Galveston and back.... I'll see... I need to make sure this thing is gonna make it this season at the lease... plan on using it to get back an forth to the stand....
I don't think "slipping" was the correct term..... It doesn't feel like its slipping while driving, just the big problem at dead stop climbing over the curb.....
My BIG concern now are the "chunks" in the bottom of the pan......

 

[Barrman]

3.08 axles really take away any mechanical advantage the engine might have. Especially if you added bigger tires. I have gotten to where I put whatever I am driving in Low for any incline like a trailer and for objects taller than my fist. I used to just push the loud pedal more. Driving the M35's all the time though has spoiled me to huge mechanical advantage.

The theory is that your truck was serviced when it was supposed to be by the military. Who knows what really happened. New, clean fluid with a new filter at the proper level should take care of you. Your donut shaped magnet looked like it didn't have anything on it at all. Normally, it looks like a woolly blob, then a woolly disc, then finally a donut as you clean all the metal off.

Now that you have swapped out the filter, a flush would be a great thing to do in 20K miles or so. We do them all the time here in my class. Fancy Snap-On machine that hooks into the lines. 24 quarts for that transmission. It is amazing how dirty the fluid coming out looks compared to the new stuff going in. However, all the trash in the system should be flushed out with it. That is why it cost so much. The 5-6 gallons of fluid. Check some of your local school auto tech classes. Don't even bother if they don't have a flush machine though. Try to buy some fluid in bulk and take it to them.

 

[wbdodgeiv]

I hate to necro bump but my M1009 on 33’s drives similarly to above. I can’t tell if the trans is slipping or if that’s just how it is, it’s the only M1009 I’ve ever driven. Seems fine on the road, at lower speeds the engine jumps to 1700 rpm and sits there until the truck catches up and then it climbs along with the speed. I’ve had cars with a roasted clutch and this doesn’t drive like that, it accelerates (relatively) strong from a stop and climbs curbs / obstacles fine.

My driveway is very steep (27% at the top) and if I stop reversing near the top it gets stuck and just sits at 1700 rpm making lots of noise. In drive it makes it up but barely. I think that 1st at 2.48 and R at 2.08 is the difference. In low it makes it with authority.

I did did all the pressure measurements in the -34 and it’s 20-50 psi over the book values for each test.

 

[cucvrus]

I would remove the transmission and get it gone over at a reputable transmission shop. I have everyone gone over just because they are 30+ years old and the seals and clutches are dried out and everything is not functioning as designed. I do the R & R myself to cut costs. I do it on the ground or in a garage. A floor jack and a small square of 3/4" plywood is all you need. Do take the transfer case off to lighten up the assembly. A word of caution. removing the adapter from the transmission can take the threads out of the transmission case. So don't do it if you don't have to. They can rebuild it properly with that adapter in place. Good Luck.

 

[wbdodgeiv]

If the bands were slipping wouldn’t it rev over the converter stall rpm at a standstill? The shifts are also firm. It reminds me of driving my dad’s Corolla w/ a CVT. Engine stays in the torque band and the car accelerates. Feels mushy / slushy if you jab the throttle.

Is ~1700 the correct TC stall rpm, I couldn’t find it in the TM’s. 1700 came from a SS post about picking a TC.

 

[cucvrus]

I don't know any of that. I know it don't shift and slips it's time for rebuilding. I am a parts replacer. I do what I know how to do and let the rest up to professionals that know what they are doing. I have not worked in a GM garage since 1988. Lots of things have changed since then. I just pull it out most times before it goes bad. And I get it rebuilt on age alone. Head gaskets are the same way. Change them as a precaution at this point in time. Good Luck. I hope everything works out for you.