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Built tranny going bad

8K views 80 replies 17 participants last post by  PSDfan99 
#1 ·
Well my tranny is clearly slipping at high speeds. Tonight I was going about 70mph in OD accelerating fairly hard and the RPM's clearly rev'd and the tranny felt disconnected from the engine. I let out of the throttle and it was fine.

If you drive normal the tranny is perfect, and even from a stop under hard acceleration it's solid. When driving at high speed under hard acceleration it's slipping. In Drag_3B it shutters off the line, and you can feel it, but no other tunes do this.

Is this a torque converter issue, or something else?

The tranny has never been overheated, it usually runs around 130º-170º depending on the outside temperature. Shifts are firm and strong, torque converter lock-up is strong..... only slips at high speed in my hot tunes under hard acceleration.

Tranny has 30k miles on it since rebuild by a very good trans builder here called Mass Diesel Performance. I need to call them in the morning to pick Scott's brain, but I want to hear what you guys think.

Please help me, I don't know what components are slipping.
 
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#3 ·
Thanks Tony. I suspect the converter, but I'm not sure because transmission issues are something I've never really had to diagnose or repair. This tranny has been awesome for the past 30k, until I added all this new power (injectors and turbo).

I'm going to call Mass Diesel at 8:30am and see what Scott thinks and maybe take a test drive.
 
#5 ·
I took the truck about 60 miles into Boston and back tonight to get the GF at the air port and the truck shifts, drives, and runs beautiful if you're not in a hot setting on the chip and trying to do a speed run. Normal driving it's perfect, at WOT or very hard acceleration in OD, when the boost builds you can feel the slip.... let out and its fine.

As for converter upgrades... I want the best for my application, or darn close to the best. Currently I'm running a single disc DTT converter.
 
#9 ·
Ok, so the overall consensus is that the TCC is the problem? Just want to be sure of that before spend any money on a PI.
 
#10 ·
Ok, I just went for a drive with the scan tool and watched the TCC lock up % to see if it was doing the slipping or if it was something else. The TCC lock never slipped. It stayed at 100% from the point of lock up even through the "slipping". I talked to my tranny guy and he said the best way to check a slipping TCC is to watch the % of lock up when the slipping occurs... so I did and it held 100% the entire time.

What do I do next?
 
#11 ·
I think there is a way to watch shaft speed but not sure.Don't know if that would help you out.

I would agree with everyone else and say TC.The bad thing is the damn thing will take out the rest of the tranny after time.

What does the fluid look like?What fluid do you run?I know Brian@BTS does not recommend synthetics in High HP applications.

I went through 3 trans.1st stocker never had a chance.2nd ford reman.Nothing wrong with it.Just had the money for a BTS at the time.
 
#13 ·
When a tranny shudders (like in 2nd gear under moderate acceleration) what does that mean? What is slipping when you can feel a shudder throughout the truck?
 
#14 ·
Is it still under warranty? 30k is not a lot of miles. I hope you are able to sort this out.

Tom
 
#16 ·
Nope, warranty was up on June 14th... 2 years since the build.

I'm honestly not looking for warranty to cover it, when it was built my truck was stock with a TS chip.... I'm far from stock now. It's been wonderful until I added the hybrids and tuning and turbo.

If it's a converter issue... great, I'll put a new and better one in it.
If it needs a rebuild........ not so great, that's a bunch of cash.
 
#15 ·
convertor or input drive is failing.........my opinion
 
#17 ·
Talk to scott. It sounds like a converter issue.

Think of it like this. On a stick car, its the clutch that holds the power. When you put the pedal to the floor and the RPMs rise and speed does not increase in sync, you have a slipping clutch.

During t/c lock, the coverter clutch takes the place of the clutch. When you put the hammer down, it slips. To me, you need a triple disc. Usually scott recommends those. He did with my build, but i already had one. Also, i dont know what he put in your trans.

Does it slip between shifts @ WOT? If not, its almost 100% has to be the converter.

I got a full tugger kit, race clutches/pressure plates, billet input shaft, billet forward drum, new pump gears, etc.

I'm pretty sure he didnt put all that into yours. Do you know if you even have a shift kit? BTW if you have a tugger kit you dont need the pumps mods...

I would change the converter anyway, if its been in there for 30k, its probably already tired from the new added power. Go with a PI and never look back.

Just curious, have you checked the fluid lately? Condition? Level?

FWIW, mine has never seen over 155*. The only time it got that hot when it was well into the 90s outside. It usually runs 120-145 or so. 70-80* above ambient.
 
#18 ·
I can't respond to this right now I'm very late for a 4th party (on the 3rd) so I'll reply in depth in the morning when I'm at work with a very bad hangover. Talk to you then!
 
#22 ·
Well this makes me feel much better about the slipping issue. I'm praying that it'll be the TCC.
 
#23 ·
First off, what is ISS, and can I monitor it through the datastream on my scanner? and secondly, what should I be looking for?

I'm using a MAC Mentor btw.
 
#25 ·
Well I just got back from a ride with my tranny builder and he sat in the passenger's seat with his scanner and watched for anything goofy going on with the tranny. He said he couldn't find anything out of place at all and that the slipping is very likely the TCC. This is somewhat good news because if it wasn't a TCC issue, I'd probably be shelling out thousands of dollars for another build.

Thanks for all the help guys, tomorrow I order a torque converter.
 
#26 ·
A 65 lb. purple torque converter came to my house, thank you Diesel Innovations and PI. tomorrow afternoon she goes in.

I'll report back.
 
#29 ·
We I did the torque converter yesterday and wow, what a difference! When this thing locks up it really pulls hard.

but.....

The high speed slipping I was having is still there. In Overdrive, heavy on the accelerator pedal, as soon as the boost starts to come around it slips. By the time it does it I'm usually going about 70-80 mph.

Let out of the throttle or turn down the chip and it doesn't slip.

From the sounds of things, I have smoked my OD clutches. This really sucks, because I thought for sure the TC was going to solve my issues.

The PI rocks though.
 
#31 ·
Yea I don't think Scott likes me too much. We got into a pissing match a few weeks ago about the tranny slipping issue so I don't think any favors will be had on my part. I'll definitely have him do the repairs because he's probably the best tranny guy around, but I highly doubt anything will be done under warranty. I'll probably pull and install the tranny myself to save on labor cost and just have him bench job the thing.

I need to talk to Swamps tomorrow and then call Mass Diesel after I talk to Dave and Jon.

Faahk this suck.
 
#32 ·
What did he say about the slipping problem?? Did he ever tell you what he put into the build??

I'd see if Jonathan can bump up the line pressures to see if it makes any difference....probably wont, but worth a try i suppose.

As him what he put into my tranny...tell him i'm a friend of Dez's and he built my tranny over the winter.

AFAIK, i have a billet input shaft, billet forward drum, Full Tugger kit, Hardened steel planetaries, good clutches/pressure plates. I also got new pump gears when he built it. I told him i need it to handle 600+rwhp. He said it should hold it with this stuff. He did say dont expect to get 200+ passes on it without rebuilding it...I've gone down the track probably 20-25 times in my life, and only a half dozen or so with this tranny. We'll see how it likes the new found power once everything is dialed in.
 
#33 ·
Well Scott and i went for a 15min test drive with his scanner hooked up and he monitored everything the tranny was doing. I got the tranny to shutter and slip several times and he honestly said he couldn't see anything at all out of place, which made him believe it was the TC. I need to contact Swamps about the tuning/ line pressure etc.

I don't really know why this tranny would be smoked in 30k miles. I've only been in the 350-450hp range for like 12k miles and only recently more with the new turbo. The truck has been daily driven easy and the only work it sees is when it snows out and I plow driveways with it and the tranny never gets "hot".

It just sucks that when you take care of your sh*t like I do and then all of a sudden it fails on you for no real reason. I'm more disappointed than anything right now.
 
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