dreamer1q

I posted this in tech and got no answers and 9 views in 2 days. I feel this is advanced, so here it goes. Any help would be great. Thanks in advance.


I have been going through the searchs of converting to a th350 trans. Two problems I cant figure out. First the speedo. I realized you can get the parts through Dakota Digital for a huge amount of money. But someone also said you can use GM part numbers 8655315 and 8655291 and make it work. But if you use those parts from GM, are you going to have to retain the A4 programming in the ECM? I want to do away with the A4 file so as to avoid the high stall problem associated with OBD1 ECM's. Is it possible to switch from a 40 tooth reluctor to a 17 tooth reluctor and make it work and believe it is a M6? If so does anyone know where you can get a 17 tooth reluctor? Second problem I have is fairly small. I have heard different stories about the dipstick. Will a stock one work? or a stock one from the th350? If not, where can you get a dipstick that will work?

onebad96T/A

I have done the TH-350 conversion from a 4L60E
Question #1
I used a kit that has a diffrent out-put shaft and comes with a 2" spacer that goes between the tail shaft housing and the tranny case this kit allows you to use the stock DS and use the factory speedo the only thing i did have to do is change the plugin on the wiring harness, (simple change) i got one off an old 700R4 for free and the speedo works like a charm. My local tranny shop built the tranny and installed the conversion kit.
The pice was around 150$ for the conversion kit, I do have the part # and the name of the manufactor i got it from if you need it

Question #2
I used a Lokar flexable tranny dip stick tube they are a little high but they are worth it because you can mount the dip stick any where you want. im not sureif the stock one works or not didnt try it.

One thing to add i just converted to an OBD1 PCM from my OBD2 and i had them delete the A4 tranny so it will stop throwing codes, so now i dont know if the speedo is going to work i guess i will find out this weekend!

dreamer1q

Great info, that helped alot. I had thought of the Lokar before but wasnt sure it would work. I would love a link and the part number on the parts you used. And PLEASE let me know if your speedo still works. That is one of the main problems I am having is wondering if it will work once I delelte the A4 program in the ECM. I want to run a high stall, but dont want the problems with a OBD1 to bite me, but if it screws with the speedo I dont know what I can do. Please keep me informed on this one, I look forward to hearing what happens.

Q

onebad96T/A

I will post the part #'s when i get back from my shop later this afternoon, and i will let you know when i get the PCM put back in this weekend i should get the OBD1 PCM from PCMforless.com tommorow.

dreamer1q

Sounds good, I will wait for ya.

BOOSTEDGTA

get the madman dipstick tube, it is more easily accessible and puts in the stock (A4) location in the engine bay. as for those GM part #'s for the speedo, i believe that is for the TH400, not the TH350. i only know of 2 ways to hook up the speedo for the TH350--Dakota Digital stuff or make your own using a Radio Shack operational amp. i have yet to hook up my speedo, but i would like to hear more about what was mentioned above using a plug off a 700r4??

CANTONRACER

Get a Lokar 36" dipstick....

rskrause

Most TH350's does not have a lockup converter. If you are installing a non- lock up version, the programming is irrelevant. The lock up version can be controlled manually, probably the best way to do it. TCI also has a kit that will control lock- up automatically. The lock up converters are not as strong as the non-lock up and generate more heat.

This should not be in Advanced Tech as it is pretty basic.

Rich

Injuneer

I looked at posts over the last 3 months and couldn't find any regarding a TH350, or any on the Drivetrain forum. I wonder which "tech" forum it was posted in?

Moving to "Drivetrain".

n20ta2

You need a vss translator from dakota digital and mine was only 35-40 bucks wired it into the existing harness for the speedo and the thing worked perfectly. as for the trans if you use a TH-350 with a 9" tailshaft it will bolt in using the stock shaft. A 9" tailshaft core trans should be easy to locate if you havent bought a trans yet. I had my trans program eliminated from the pcm and it also cured the stall wall problem from my 3500 stall converter.

400hp ss

You can use the stock dip stick that what i use in my car the th350 is a good tranny what gear are you going to run with it? You can also use the stock crossmember you just mod the mount on it. I hope you get a stout th350 the one in my car had all the best parts in it any today on the dyno i snaped the case right in half at the bellhousing theirs $2000 down the drain.

rskrause

I never understood the logic of a TH350 swap. If you need a storng automatic and are resigned to losing the OD, just go for a TH400 and be done with it.

Rich

400hp ss

The 400 is stronger but you know that it takes 50 hp to turn over the th400

revtime

[QUOTE] i snaped the case right in half at the bellhousing theirs $2000 down the drain.[QUOTE]

If the case snapped then it did not fail internally. Maybe a cracked bellhousing.
I may run a built TH350 just to see if it will last longer than my built 4L60E, which lasted 26k behind my bolt on high mileage LT1.

The TH400 does take more horsepower than a TH350 but a TH400 is 28 lbs LIGHTER than a 4L60E.
I wonder how much horsepower it takes to spin a 60E?

rskrause

I don't believe that there is any possible way that it would take 50hp more to spin a TH400 than a TH350. Most of the drivetrain loss from adding any automatic is the converter. There is very little internal drag. Yes, the TH400 parts are larger and heavier and therefore have more inertia. But the parts are not that heavy and they are all small radius, so it just isn't going to take that kind of hp to turn them. 50hp would be a 12.5% ADDITIONAL loss for the tranny alone on a 400hp setup and I find that very hard to accept. A TH400 setup might loose ~20% total drivetrain loss, so by switching to a TH350 the net drivetrain loss would be 5%?? Does not make sense.

Where does that 50hp figure come from?

Rich