Question about Rebuilt(?) TH-400

[HelluvaEngineer]

Over the past 2 years I've done a lot of work on my M1009. I finally got it back from the body shop and was hoping to enjoy putting some miles on it. It rewarded me by failing to go into reverse. First it was sometimes, then always. The transmission was whining. I didn't really think about how much it was - I wasn't sure if it was the transfer case chain as this is the first one I've ever owned.

I took it to a local family-owned shop that had good reviews on Google. They reported back it had "metal in the pan". Interesting since I changed the fluid and filter maybe 300 miles back. The shop told me "grandpa" was going to work on it because he knows all about TH400s. That seemed like a good thing.

I got it back in about a week and a half, with little details, other than it needed a new modulator. It was smooth at first (maybe 50 miles). No noise. Then I noticed on cold mornings R was whining, as well as the first couple miles of driving. Then the fluid would warm up and it would shut up. The kickdown doesn't seem to be working properly. I have to stomp it on hills to get it to drop down. I realized today it was actually taking off in 2nd gear, and acceleration is bad.

Any advice on what to do? They said it has a 1 year "warranty" but I'm worried they will toss sawdust in it if I take it back without additional understanding of what should be happening. For example, I'm wondering if he put a gas modulator on not understanding that diesels don't have much if any vacuum. Also thinking the pump should have been replaced. Thanks for all comments!

 

[HelluvaEngineer]

I just saw online that white stripe modulators are for diesel. Heading out to look at the truck...

Update: no white stripe. I also noticed the cotter pin for the gear selector was never folded over and is about to fall out. Great.

 

[Skinny]

Modulator has nothing to do with the engine or it making noise in reverse. All it does is adjust line pressure based on the engine load.

If it is failing to engage then you either have a physical problem with the clutch pack or a valve body problem not applying pressure. Either way it is most likely a need a rebuilt that regardless. You should avoid that shop and fine a qualified place.

I just went through this whole ordeal as I swapped a 4L80 into my truck. Bought it from a place that talked it up only to find out that the entire thing was completely smoked. I taught automatic transmissions for over a decade but I do not have the shop space to do this. I had to outsource it and found a guy with a nice clean place that was very knowledgeable.

I have a good turbo 400 that just came out of my truck that has 20000 miles on it. I would sell it for a few hundred bucks if you would pay the shipping or would pick it up. Located in southern NH.

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[cucvrus]

TH400 4L80E Rear Reverse Band

GM 4L80E Rear Band by Raybestos

globaltransmissionparts.com

I am going to ask. Did they rebuild the transmission? And did they adjust the vacuum? It sounds to me like the reverse band in the transmission is worn out and the entire transmission needs taken apart. After over 30 years seals and clutches just wear out and fail. Flushing and changing filters at this point is a waste of time. Get the transmission rebuilt at a competent transmission shop. I get every transmission rebuilt on every CUCV I refurbish. It is $7-800. of money well spent when the truck is very reliable and shifts as designed. Don't wait for a catastrophic failure. It gets more costly as things continue to self destruct. Good Luck and do it right the first time. Sawdust in the transmission is failure of communication. Get the transfer case gone over at the same time. It is less expensive now when you have it out.

 

[HelluvaEngineer]

TH400 4L80E Rear Reverse Band

GM 4L80E Rear Band by Raybestos

globaltransmissionparts.com

I am going to ask. Did they rebuild the transmission? And did they adjust the vacuum? It sounds to me like the reverse band in the transmission is worn out and the entire transmission needs taken apart. After over 30 years seals and clutches just wear out and fail. Flushing and changing filters at this point is a waste of time. Get the transmission rebuilt at a competent transmission shop.

To clarify, I spent about twice what you mentioned to have the transmission rebuilt. It would not go into Reverse at all when I took it in. After the "rebuild" it went into R and shifted fine. What concerns me is that when it sits a few days and I put it into R to pull out of my driveway, it whines. Same when I initially put it in drive once out of the driveway. It shuts up after about a mile.

The kickdown is a real problem. It's taking off in 2nd gear for some reason and is not downshifting on large hills, etc.

I guess I'm wondering if I should take it back to the shop, call my credit card company, or if somehow a rebuilt transmission can be expected to whine at startup.

When I spoke to the guy who rebuilt it on the phone, he claimed to be familiar with them and the chain drive xfer case as well. I'm hoping this is something "fixable" without another rebuild from another shop.

Also, to clarify, it seems to engage all gears without hard shifts.

 

[cucvrus]

It has issues. The issues need resolved or further damage will occur. Use caution when choosing who works on anything you own. Good Luck. GA is a long way off. I would assist if I could. Take Care. I have a few rebuildable cases here. Not burnt out but I don't sell or install used Automatic Transmissions period. Never.

 

[nyoffroad]

To clarify, I spent about twice what you mentioned to have the transmission rebuilt. It would not go into Reverse at all when I took it in. After the "rebuild" it went into R and shifted fine. What concerns me is that when it sits a few days and I put it into R to pull out of my driveway, it whines. Same when I initially put it in drive once out of the driveway. It shuts up after about a mile.

The kickdown is a real problem. It's taking off in 2nd gear for some reason and is not downshifting on large hills, etc.

I guess I'm wondering if I should take it back to the shop, call my credit card company, or if somehow a rebuilt transmission can be expected to whine at startup.

When I spoke to the guy who rebuilt it on the phone, he claimed to be familiar with them and the chain drive xfer case as well. I'm hoping this is something "fixable" without another rebuild from another shop.

Also, to clarify, it seems to engage all gears without hard shifts.

You paid for a rebuilt tranny and have a warranty for a reason, use it! I know, I know I wouldn't be to happy about going back there either but money is money and business is business. Give them a chance to fix it before charging it back on your card. And NO it should not whine! When it gets fixed get a list of everything thats replaced and that should be all new clutches and steels , 1st and reverse band and a NEW or rebuilt torque converter. Do not settle on "well we replaced the TC when it was rebuilt the 1st time" if the ATF has metal particles in it they will also end up in the TC and ruin a new rebuild. good luck!

 

[LT67]

Over the past 2 years I've done a lot of work on my M1009. I finally got it back from the body shop and was hoping to enjoy putting some miles on it. It rewarded me by failing to go into reverse. First it was sometimes, then always. The transmission was whining. I didn't really think about how much it was - I wasn't sure if it was the transfer case chain as this is the first one I've ever owned.

I took it to a local family-owned shop that had good reviews on Google. They reported back it had "metal in the pan". Interesting since I changed the fluid and filter maybe 300 miles back. The shop told me "grandpa" was going to work on it because he knows all about TH400s. That seemed like a good thing.

I got it back in about a week and a half, with little details, other than it needed a new modulator. It was smooth at first (maybe 50 miles). No noise. Then I noticed on cold mornings R was whining, as well as the first couple miles of driving. Then the fluid would warm up and it would shut up. The kickdown doesn't seem to be working properly. I have to stomp it on hills to get it to drop down. I realized today it was actually taking off in 2nd gear, and acceleration is bad.

Any advice on what to do? They said it has a 1 year "warranty" but I'm worried they will toss sawdust in it if I take it back without additional understanding of what should be happening. For example, I'm wondering if he put a gas modulator on not understanding that diesels don't have much if any vacuum. Also thinking the pump should have been replaced. Thanks for all comments!

Find another shop...

You're in Atlanta, so finding someone that knows how to properly rebuild an older transmission will not be easy. I'm out on the western side of Carroll county which is about an hour from Atl. I have a very good mechanic out here on the south side of Bowdon that I highly recommend. He's also cheaper than the shops in Atl. If you want his contact info, shoot me a private message.

 

[gringeltaube]

... and if you need a new T-C, contact Gimpy (member @gimpyrobb).

 

[HelluvaEngineer]

You paid for a rebuilt tranny and have a warranty for a reason, use it! I know, I know I wouldn't be to happy about going back there either but money is money and business is business. Give them a chance to fix it before charging it back on your card.

Thanks. I appreciate all the advice here. It's going back on Thursday. "Grandpa" didn't want to talk to me on the phone but I heard him in the background and he was concerned about how far I was away from the shop. He knew he screwed something up.

 

[HelluvaEngineer]

I'm out on the western side of Carroll county which is about an hour from Atl. I have a very good mechanic out here on the south side of Bowdon that I highly recommend.

Would be great but I'm actually up in Cherokee county. Over 2 hours to get to Bowdon. Thank you though.
I wish there was a place around here I could rent rack space for about a month and knock out this and other projects. I hate not having a shop.

 

[HelluvaEngineer]

Just took some pics of the leaky pan, leaky cooling fittings, reused vacuum line, and the best is the cotter pin. I gave them a new pan with magnetic drain and they didn't install it. This kinda stuff drives me nuts... At least it's a good pan gasket.

 

[LT67]

Would be great but I'm actually up in Cherokee county. Over 2 hours to get to Bowdon. Thank you though.
I wish there was a place around here I could rent rack space for about a month and knock out this and other projects. I hate not having a shop.

I know some people up there, I'll ask....

What part of Cherokee?

 

[HelluvaEngineer]

I know some people up there, I'll ask....

What part of Cherokee?

I'm in the SE section, literally on the Little River on the border with Milton.

 

[Sharecropper]

I swear, from what I have read, I don’t believe I could take it back to Grampa. If there is a way to stop payment on your credit card, I would do it and inform Gramps that you are. I would then sit down and document everything that happened in chronological order. Give Gramps a copy. But move on to a reputable shop and get your transmission rebuilt. Just my 2 cents.

 

[Mainsail]

I'm wondering if they rebuilt it or had a fair used one they just swapped in. Are you sure that's the same trans you gave them?

The advice I was given long ago was to always ask for the old parts back- tell them you want to see how bad they were. Kinda late for you now, but something to think about in the future (assuming they still allow you to have them back).

I would head over there and talk to them in person- your gut should tell you if they want to do right by their customer or are just blowing smoke up your butt. For all you know, granadpa might be upset and wanting to make it right.

 

[LT67]

I'm in the SE section, literally on the Little River on the border with Milton.

A friend over there recommended a shop called Landmark in Roswell off of Alpharretta St

 

[HelluvaEngineer]

A friend over there recommended a shop called Landmark in Roswell off of Alpharretta St

Thank you very much. I will look into it. Their website looks promising.
I am taking it back to the original shop to see what they do. On Thursday.

 

[LT67]

Thank you very much. I will look into it. Their website looks promising.
I am taking it back to the original shop to see what they do. On Thursday.

You mentioned a whining noise; have you checked the fluid level in the transfer case?

 

[Skinny]

I just pulled mine using a $99 Harbor Freight jack. $350 plus freight gets you a very low mileage unit that works fine.

Sorry all the haters can hate because they dont install used stuff. Stop the presses, all the salvage yards are closing because its all junk. Notify LKQ...

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