Th400 going bad?

[ssdvc]

My trans was doing some of the same things. Would drive fine most of the time, but every so often she would start acting up. While She is down with Rick getting serviced, he suggested it get looked at. Turns out it needed some work (a lot of work from last report). At least going forward, that will be one thing I don't have to worry about.

 

[2INSANE]

Do they have an output shaft to fit the stock tcase? I've done one for a np203...I was thinking of doing a 4L80E for my 1 ton truck but haven't looked into it yet.

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I found a $300 junkyard 700r4/np241 already mated to a 6.2 diesel so it should bolt right in. The only thing I’ll have to change is the driveshafts.

 

[cucvrus]

Do as you wish. At this point I would NEVER go thru the trouble bolting in a used transmission and torque converter. The work and risk are not worth the effort. Get the transmission gone over and be sure it is in excellent condition. Once you do that overhaul you can drive on with the confidence that you done the right thing and it will last for years to come. Good Luck. I would not sell a used transmission to anyone anymore. I just reminded myself yesterday that I have a CUCV M1009 that were built 38 years ago. WOW.

 

[cucvrus]

turbo hydramatic 400 rebuild kit - Google Search
Amazon.com: Compatible With: Chevy GM Chevy GM TH400 Alto Transmission Master Rebuild Kit Level 2 : Automotive
TH400 diesel torque converter - Google Search
I was looking at parts to rebuild a TH400. Just to look and get a real life price. I can't imagine overhauling a transmission without replacing the torque converter. I still think a realistic price for a complete overhaul with the transmission on the bench is close to $800. $1000. That is doing it right and no short cuts. Getting the radiator cooler flushed is also a much needed process, Unless you like all the funk and gunk from the old transmission floating thru your new transmission. Good Luck on your home brew overhaul. I think wise men spend the money up front and move on for years to come. The sting of a higher price is out weighed in the reliability and durability. Take Care and Have a Great Day. Enjoy the Holiday weekend.

 

[LT67]

I found a $300 junkyard 700r4/np241 already mated to a 6.2 diesel so it should bolt right in. The only thing I’ll have to change is the driveshafts.

Have fun making that 700r stay together with that turbo diesel lol

 

[Sharecropper]

Have fun making that 700r stay together with that turbo diesel lol

Hey LT - if a 700R4 is built correctly, it will stay together fine on a turbo diesel. For my P400 build, I opted for a Level II K-case 700R4 from Bowtie Overdrives in California rated for 450 HP and 450 FPT. After I get my Bullet Supercharger installed, my P400 is estimated to be rated around 300 HP. I think the mistake most guys make is to use a stock 700R4 on a strong engine which usually results in failure.

 

[LT67]

Hey LT - if a 700R4 is built correctly, it will stay together fine on a turbo diesel. For my P400 build, I opted for a Level II K-case 700R4 from Bowtie Overdrives in California rated for 450 HP and 450 FPT. After I get my Bullet Supercharger installed, my P400 is estimated to be rated around 300 HP. I think the mistake most guys make is to use a stock 700R4 on a strong engine which usually results in failure.

Yes, they have to be modified to handle the power. In stock form they're a time bomb waiting to go off. Just like a 10 bolt G80 gov-loc.. lol

 

[chevymike]

Bowtie Overdrive has built some good units. I had one in a '68 C10 truck I built 20+ years ago. They were really new on the aftermarket trans scene, as there were not many doing 700R4 back then.

One thing to note, the TV cable (it is not a kick down cable) MUST be setup 100% correctly. It controls all of the line pressure and if not setup right, you can burn up a trans in a few miles. This is the biggest mistake most people make, thinking it is like a TH350 kick down cable. Luckily there is a guy who works at Bowtie who has a M1008 so he should know exactly what you need to do.

 

[Sharecropper]

Luckily there is a guy who works at Bowtie who has a M1008 so he should know exactly what you need to do.

That would be Chris Gardner. He owns Bowtie and drives a M1008 daily. He knows his stuff. I will lean on him when the time comes for me to crank my rig.

 

[2INSANE]

Wow! Thanks for all the positive feedback gentlemen! No need to stress!

I got the 700r4 pulled this last Friday and took it straight to the Transmission shop for a full rebuild. They will put the best of the best parts in it and slap a 3 year, 36,000 warranty on it. Also new torque converter. $1750 I paid them cash and they are 5 weeks out.

The 700r4 from the junkyard 6.2 85 Burb also had a NP208 already bolted to it. SCORE!

The low first gear on the 700r4, low gears on the NP208 with my 4.56 gears will be slug slow for the rocks! But the 4th OD should get me to 75mph on the hwy.

I have a np205 but don’t want it because of the weight and higher gears.

700r4 is lighter then the th400 as well. Weight reductions are always good.

Another positive about this swap is I can get rid of that crap vacuum system on the M1009 and replace the vacuum pump with a 6.5 oil pump gear drive with the Tachometer sensor on top to get my Phantom 2 tachometer to finally work after all these years.

 

[WWRD99]

That sounds great! 1750 for a built 700 isn't horrible...with the higher grade hard parts that get put in them it bumps the price up a bit plus these are figured out...you tell them what you're gonna do with it and they can match it up...that lower first gear will be real nice plus the od...having the tcase on it makes the swap very easy too...one less part to swap!

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[2INSANE]

To end this thread…

After talking with you awesome SS members and getting info from you much more knowledgeable gents then I and talking to the the Transmission Shop…

We have concluded that the TH400 is still good but the torque converter stall values are not correct for the 6.5 Optimizer causing the shifting issues.

And with this soon to be 700R4 swap… This TH400 is now up for sale!

 

[Sharecropper]

You will be happy with the 700R4. Make sure you have the TV cable adjusted correctly. And make sure when you press the accelerator pedal to the floor, the IP throttle is actually all the way open. This is important in order for the 700R4 to downshift properly. Just because the pedal is floored, that doesn't necessarily mean the throttle is wide open. You may need to bend the hinged pedal rod slightly so that the pedal bottoms out before it hits the firewall.

Speaking of rods, do you have the transfer case support rod?

 

[2INSANE]

You will be happy with the 700R4. Make sure you have the TV cable adjusted correctly. And make sure when you press the accelerator pedal to the floor, the IP throttle is actually all the way open. This is important in order for the 700R4 to downshift properly. Just because the pedal is floored, that doesn't necessarily mean the throttle is wide open. You may need to bend the hinged pedal rod slightly so that the pedal bottoms out before it hits the firewall.

Speaking of rods, do you have the transfer case support rod?

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Great info! Thanks! Yes I have the rod!