TH 350 Question

[druidrv]

This TH-350 dose not go into gear and is not pumping fluid through the trans cooler. This is the second trans we have put into this truck to have the same symptom. The only thing we reused was the torque converter. The second trans was gone through with new clutches and filter. Can the lack of fluid pressure be caused by the converter? It is a near stock stall B&M around a year old with no visible damage.

[MT-2500]

Fluid level full when engine running in park?

If no cooler line pressure speed engine up just a little.

Have you check transmission pressure?
If no pressure front pump may not be pumping.
Is the pump gear tabs broke off.
Did you have converter end play when transmission bolted up?

[SLJ2137694]

Originally Posted by MT-2500

Fluid level full when engine running in park?

If no cooler line pressure speed engine up just a little.

Have you check transmission pressure?
If no pressure front pump may not be pumping.
Is the pump gear tabs broke off.
Did you have converter end play when transmission bolted up?

Good point about the torque converter that may not be properly indexed to the front pump. I have seen this happen more than once by some inexperienced wanna-be technicians.

[silicon212]

... and it results in death to the front pump.

[druidrv]

Wanna be tech. I may not do this for a living but this is not my first dance either. The trans went in fine and no I did not pinch the converter. The question was, can the lack of fluid pressure be caused by a defective converter. If not, then the trans was rebuilt wrongly by a real life, professional tech.

[silicon212]

The torque converter must be properly indexed in the transmission. There are three 'clicks' on a perfectly indexed converter - the first when the input shaft indexes, the second when the stator indexes and the third happens when the front pump indexes. You may think it's fully indexed, and indeed the converter will fit between the flexplate and transmission (without binding) if the input and stator are indexed but not the pump. It's easy to miss if you're not 100% careful, such as if you're in a hurry to get it on the road; I've been guilty of that myself once which is why I can write about it here. I hope you don't view this post as a knock on your skills - it isn't.

A failure of this type is considered an install failure, not a build failure, so your trans tech is not responsible if you installed the transmission yourself.

Of course, this is all hinging on whether or not the front pump (broken gears) is the problem. There are other things that can cause this - low oil level (did you put at least 8 to 12 quarts of fluid in it when you installed?) is a chief culprit.

8 quarts if you're reusing a torque converter, 12 quarts if you have a new/rebuilt converter.

[MT-2500]

Originally Posted by druidrv

Wanna be tech. I may not do this for a living but this is not my first dance either. The trans went in fine and no I did not pinch the converter. The question was, can the lack of fluid pressure be caused by a defective converter. If not, then the trans was rebuilt wrongly by a real life, professional tech.

The converter does not pump up the pressure.
It job is to turn the front input shaft into the transmission just like the input shaft on a standard transmission.
Only it is coupled to the engine with hyd. turbon fins instead of a solid disk.

The front pumps pumps up the hyd. and line pressure in the transmission.

[druidrv]

No offence taken on my skills as they are extremely limited. Thanks for answering the converter question. I didn’t think it was the problem. I never had a problem indexing the converter before, but we were pushing to get it back on the road. I will double-check the indexing. That is probably the problem. Many thanks for the info. Ron

[MT-2500]

Originally Posted by druidrv

No offence taken on my skills as they are extremely limited. Thanks for answering the converter question. I didn’t think it was the problem. I never had a problem indexing the converter before, but we were pushing to get it back on the road. I will double-check the indexing. That is probably the problem. Many thanks for the info. Ron

You are welcome.
Make sure it is full of fluid and put a pressure gauge on it and if no pressure it will have to come back out.
If you pull it back out open up the front pump and chech the pump gears.
If yhey are OK you will have to go deaper in it .
Good Luck
MT

[bobss396]

From my experience with a torque converter not being "home", it has been obvious and can prevent you from bolting up the transmission to the engine. I always replace the converter when I swap a transmission, I used to get a good deal on rebuilt ones at my local Aamco.

I have made up a couple of simple brackets that hold the converter in place while I install transmissions. It bolted to one of the flywheel inspection pan holes, had a slot sawed in it that picked up one of the mounting brackets on the converter. You should have around a 3/8" gap between the flywheel and the flex plate once the tranny case is bolted up to the block. Which will difer from model to model.

Bob