transmissions slips until warmed up. How to replace?

[SmokeyDod]

Glad you made it. As to the filter, sometimes you really can't tell how it looks with the small opening. Go ahead and get a new one and 2 gals of fluid and try it. You just don't realize how much you're getting into taking it out and rebuilding it. Also the cucvs all have the "HD" transmission case. It has HD stamped on top of the case. That's why it takes the hd alum cover plate bolted to it. If you get one on Craigs List. 1)What are you getting?? What the real condition of it. ???

When you have trans that is slipping, I highly suggest you don't drive it while it's slipping because that it wearing the clutch plates in it. I suggest you just let it idle for a while to warn up and its not wearing plates. While you are under truck just take a look at the linkage to make sure that nothing loose and that all is as it should be from a visule view.
Good luck again.

 

[combat jump]

Smokey, and all, thanks for the info. The good news is that I made it home, 400 miles from SoCal. The bad news? I pushed my luck too far, and drove to work today with the truck. Cold rain kept me from taking the CBR600RR, and I started to feel some slipping on the highway. 15 miles to work. 10 hours later, the truck starts, and runs ok in reverse, but only creeps forward. I warmed it up for 20 minutes. Nothing. Called for a tow. Tomorrow morning (Saturday), I'll be dropping the pan, swapping the filter, checking for crud, adding a magnet and drain plug, and doing a whole flush through to clean out the torque converter. I'll let you know how it goes.

 

[fitz]

Glad to hear you made it home from the big trip. The local tow should not be bad.
Cucv freak was more than willng to come through for you in a pinch, how cool is that.
As far as the tranny, the quickest way to get your rig back on the road is with a used tranny. Sounds like an easy weekend project. To remove, rebuild, and replace your tranny over a 3 day weekend sounds a little optimistic (I've never rebuilt 1 myself)
I've never done a tranny r&r on a cucv but I've done a few on gas job 73-87 chevys. A few things that may help.
1)Once the truck is set up at working height on ramps/jack stands, support the engine oil pan so the engine does not tilt to far and cause fan/fan shroud problems.
2)Unless you have the flywheel turning wrench (about $25 at Napa) most of us use vice grips to turn the flex plate to get to the torque converter bolts. Be carefull not to damade the teethe on the flex plate.
3) Grab some steel tranny line and a few compression fittings before hand incase you run into problems.
4)Take a look at how your exhaust is bent up to see it you can clear the tranny and transfer case comming out as 1 unit. If it won't clear grab some exhaust couplers and clamps so you can cut & reconect the exhaust pipes rather then dealing with the manifold bolts.
5) you can use some threaded rod placed finger tight into the back of the engine block to act as guide pins when you go to reinstall the tranny.
6)Try to clean your tranny lines/cooler to remove any debris from your old tranny.
7)See if the new used tranny is from a deisel. I thing the converter stall speed and the tranny shift points are different on a gas truck
I personelly find it easier to remove the tranny/transfer case as 1 unit but I install them seperatly.
These are just a few things to keep in mind. It should be an easy weekend job.
Good luck, let us know how it turns out.

 

[combat jump]

I did one last attempt to fix the transmission slipping in drive (reverse still works) before a rebuild with a flush and filter change. Jackstands up front, ramps in the rear give enough working room underneath. Cucvfreek came over to help.

I loosened the 13 1/2" pan bolts, dropping the front bolts more to encourage the fluid to begin leaking out from that part of the pan.

I used a $7 plastic "concrete mixing" tub from Harbor Freight 7 Gallon Mixing Tub to catch the transmission fluid (visible under the truck in the photo), and it got almost all of it. I had plastic sheet under that, so the driveway was kept clean.

The old cork gasket pealed right off, with no residue. There were no "chunks" in the pan, just some "mud" attached to the magnet, and some goo to scrape off the bottom. The fluid was fairly clear pink; darker than new, but not scary. No bad odor to the fluid, but not exactly like new smell.

While the pan was off, I drilled a 1/2" hole and added a retrofit transmission drain plug from Kragen/O'Reilly Auto Parts. If today's rescue attempt failed, I'd be draining this again to pull the trans.

The new gasket/filter set was only ten bucks, also from Kragen/O'Reilly. The gasket being thick rubber (not cork), and holds all the bolts nicely in place for reassembly. No RTV was used. I did wipe down the mating surfaces of both the pan and under the transmission with a carburetor-cleaner soaked rag to degrease.

Then pan went back up easily. The flush was next. I had over 3 gallons of cheap Kragen/O'Reilly Dexron fluid on hand, and a long skinny funnel to fill the dip-stick tube. The idea is to disconnect the transmission cooler return line, add fluid with the engine running and watch for the fluid to change from a dark color to clean pink. This is the only way to replace the fluid that is otherwise trapped in the torque converter.

I unbolted the transmission fluid return line from the driver's side of the radiator, and let it just hang. I then screwed in a piece of old fuel line with the same type of threaded coupling as the transmission line, and attached a length of hose with a band clamp (photo). To find out which is the fluid return line, simply follow the two lines from the transmission - the one on top is the return line. I then added a length of clear tubing to this so I could watch the color of the fluid as it pumped out (and into a 5 gallon bucket).

It helps to have two people to do this - Start the engine, continuously pour Dexron into the dipstick tube, and watch the fluid pumping into the bucket to change from dark to light pink. Stop the engine, replace the return line, then start the engine and fill the transmission with the correct level of fluid.

After doing all this, I worked the transmission through reverse and drive repeatedly, and let it warm up. Got the truck off the jackstands and ramps, and put it in drive. Nothing. Just barley rolls. Revving the engine doesn't help. Reverse is better than ever, though, and I actually did a two wheel burnout while backing up!

If anyone has any ideas for why I have reverse working great, but no drive, I am all ears. My plan is to drop the transmission next Thursday, and rebuild it over the next few days in my garage.

Finally, I have to say thank you to Cucvfreek, who came right over to help with all of this, and will help me pull the transmission. I met him right here on this forum, and he's been a huge help.

 

[combat jump]

Ok, today is "next Thursday", and I dropped the transmission. Cucvfreak came over and helped out through the entire process. It did take longer than I had expected. I have a master rebuild kit, new adjustable modulator, new torque converter, rented transmission jack, and spilled and draining transmission oil pretty much everywhere. I put a 3.5 mil plastic drop cloth under the truck before starting, and it has contained most of the red stuff.

First I put the truck on 4 jack stands. I put a piece of 2x12 under each to get more height. Removed the drive shafts, cross member, then transfer case. Its maybe 80 or 100 pounds. You don't want to get under that when it comes free of the transmission. Removing the torque converter to flex plate bolts took two people - one to hold a socket wrench on the pulley in front of the truck so it the converter would not spin while wrenching.

I put each group of bolts into a baggie and labeled them with a marker so I don't forget what they are for. In the garage, I have several tables and work benches cleared off for laying parts down in an organized way. I also bought a tech manual specifically for the THM400.

The tear down instructions call for turning the transmission pan-side up, and it wants to roll around if you don't have the special handling fixture (who does?), so I attached two 2x4's with bolts to the tail end as a stand (photo).

So, tomorrow, I'll continue the tear down, and keep you all posted.

One final thought is that I may want to replace my rear main seal, and engine oil pan gasket while this stuff is out to fix some minor leaks.

 

[wallew]

Combat Jump,

Yah, been there. Though I will admit one of my M1009's is currently sitting. I'm about to take it in to a shop to have it rebuilt, which will occur some time next week.

All the same symptoms, except I did the flush thing three times. STILL didn't matter.

Like you said, no go forward. Backs up just fine. Which is how it got to be parked where it is now, I backed it in about four months ago and there she sits.

I'll put the tow bar on my M1028A2 dually and tow it over to my guys shop. With in a couple of days, she will be road worthy again.

And I've got a second 09 and a spare TH400, both of which will need to be rebuilt. I will be doing at least one or both of those myself. But I needed to get this one on the road ASAP.

 

[combat jump]

Thanks, jdemaris
Have you changed a rear main seal? I've changed front seals on other trucks. I'm thinking its just pulling it out with a pick and pressing in the new one?

 

[combat jump]

I haven't posted in a while because I was busy rebuilding my transmission. Its done. Most of the delays were figuring out how to create some work-around tool in place of the factory special tool to compress a spring, protect an "O" ring or something. Its all together. Not to leave well enough alone, I also just dropped the oil pan and pump to replace that leaky gasket, and renew the rear main oil seal as well. I searched here for someone else's technique and have to agree with jacking up the frame, and letting the axle droop for more working room to get the pan off (on the starter motor side, at least) is the way to go. I hope to have it all together by this weekend.

 

[combat jump]

I should also mention what was wrong with the thing! The "O" ring around the forward clutch pack was broken - about an inch was gone from the "O" ring, which is maybe 6 inches in diameter. The friction plates and steels inside the forward clutch pack were also badly burnt and warped. The other clutch packs in the transmission showed normal wear. That's why I had reverse working fine, but no forward movement. I was extra careful sliding the rebuilt clutch sections together without damaging their fragile "O" rings. Not having the set of special tools to protect the rings upon installation, I cut a 2 liter soda bottle to make rings that matched the diameter of the rings I needed to protect. Then smeared transmission assembly lube on them, and wrapped it around the "O" ring while inserting. When it was all together, I then pulled the plastic out (yes, there was room) leaving the "O" rings in place and undamaged.

 

[TCUCV]

Nice job, glad to see your gonna be back up and running!

 

[combat jump]

Thanks, TCUCV. Last night, I degreased, sanded and painted (black) the oil pan. Tonight I'll get under the truck and replace the rear main oil seal. Then replace the pan, which should be fun :/ Its difficult to get to all those bolts - using a 3/8" air socket wrench, supplementing with a 1/4" ratchet for the tight spots under the front cross member. So, I degreased the pan bolts in paint thinner. Cleaning the gunk off the pan took a paint scraper, wire brush, foaming engine degreaser (then hosing it off), angle grinder with a wire wheel, carb cleaner, then finally brake cleaner. Oh, and razor blade to remove the copious RTV black and gasket.

 

[Cucvnut]

I need to change my seal also I think its missing

 

[combat jump]

JD, I haven't pulled the 4 bolts from the crank cap yet, and have not gotten a good look at what condition the seal is in - I have not removed the flex plate (and won't). I'll pull it tonight.

Also, nice going on getting your CUCV highway-ready. I had my diff gears changed to 3.73, and can cruise in the fast lane now.

Cucvnut, come on over, if you want a look at the oil seal process. Its not fun work, but gives you a good view of what all is going on.

 

[Shankem-Deep]

Hey guys, My 1028 drives and shifts fine while driving normally. Last week I tried out my new tires and lift on some really steep banks, it did great. After I got back out on the road the transmission seemed to slip while in 2nd and 3rd gear. The next day I drove it again to see if it would slip and it drove fine. The fluid level is full. Any ideas?

Thanks

 

[IdahoPlowboy]

Great info Combat Jump. Pics are great and I am now inspired to repair my transfer case.

 

[Mohawk Dave]

Need help in SoCal

Some transmission questions:

So I drove 400 miles in my M1028 this weekend to visit my son in SoCal. Then, starting up in the morning, the truck revs, but hardly moves. I topped it up with a pint of Lucas no-slip, to no avail. Then, after driving it for a mile, it starts running fine - no slipping. Park it for a few hours, and the same thing.

I am making my way back up, spending the night in Lompoc. The truck still barley crawls while revving until a mile or two are driven, then all is well. I also got a "revvvvv-THUNK" as it shifted into second once.

I think my TH400 is toast, and I hope I make it home tomorrow - 240 miles to San Jose.

My question is this: Can a TH400 be replaced without removing the engine? I have seen some used ones for sale on Craigslist for $300. What should I look for in a used TH400? Has anyone replaced their own? Any "how-to" links you can share?

I also want to thank my friend Cucvfreek for being ready to call his SoCal buds on my behalf if I really got stranded (parking my truck at my ex's house was NOT an option!)

That's way cool of Cucvfreek/cucvnut. If any of you SS guys are ever out here in SoCal and need help, no matter what hour it is, I am more than willing to leave the house and do what needs to be done. PM me if you want my phone number.

-Dave

 

[Mohawk Dave]

Thanks, TCUCV. Last night, I degreased, sanded and painted (black) the oil pan. Tonight I'll get under the truck and replace the rear main oil seal. Then replace the pan, which should be fun :/ Its difficult to get to all those bolts - using a 3/8" air socket wrench, supplementing with a 1/4" ratchet for the tight spots under the front cross member. So, I degreased the pan bolts in paint thinner. Cleaning the gunk off the pan took a paint scraper, wire brush, foaming engine degreaser (then hosing it off), angle grinder with a wire wheel, carb cleaner, then finally brake cleaner. Oh, and razor blade to remove the copious RTV black and gasket.

Just fyi, we use mineral spirits in our clean tank, so even w/o a tank, might want to try mineral spirits and some brushes. It cuts through pretty good. And so does that Industrial Purple from Home Depot. It is in a bluish/purplish 1 gallon with a chain on it. If you are in an enclosed space, I wear my canister mask b/c you can't breath.

Best wishes,

Dave

 

[combat jump]

I haven't posted in a while - been working on the transmission. Well, its in. Cucvnut and I installed it today, and it runs great. I learned a lot about transmissions, T-cases, torque converters, and that this CUCV has a nonsensical combination of metric and standard bolts.

 

[Cucvnut]

It runs great now

 

[jdemaris]

What do you mean vrv? It has the vacuum box on the ip

The VRV is the "vacuum regulator valve." It similiates the throttle-to-vauum" ratio on a diesel, like a gas engine normally does. It's what GM uses to control TH400s on diesel vehicles with vacuum pumps.

When there is no vacuum pump on the engine, mechanical modulators are used to control shifting on TH400s with diesels. Mechanical modulators get hooked to a throttle-sensing cable, but there is no vacuum invovled.