I had done searches for information on the 4L60E to TH350 conversion, but details were always sketchy and no one gave a straight answer on the speedometer issue. So, here's the summary of what I did with my conversion:

- TH350 torque converter bolts to the LT-1 flexplate.

- TH350 bolts directly to LT-1 block.

- Stock cooler lines will work, but must be "massaged" to end up in the right location.

- Madman Racing makes a dipstick tube that works perfectly - for $80.

- B&M conversion kit works perfectly ($85), except that the outer torque arm mount doesn't fit exactly right. I had to drill my own hole to install a bolt that sandwiches the rubber mount together.

- Only one hole on the stock shifter cable bracket will line up with the TH350 transmission pan bolts. Then, you'll have to adjust the cable position, much like a TV cable mechanism, to get the gears to line up with the stock shifter.

- Long tail shaft TH350 can use the stock driveshaft.

- I used a speedometer sensor from Dakota Digital. It's the SEN 01-1 and it's only $25. It installs on the TH350 cable drive outlet. However, instead of 40 pulses per driveshaft revolution, it only makes about 4. So, TunerCAT can be used to change that parameter. You'll have to do some playing with the parameters in TunerCAT to get it perfect, but that'll get you close.

Mike

 

Thanks for the info. I am thinking of using a th350 with my 383 I am buiding this summer. When you say "long tail shaft" 350 you mean the 9" shaft right? My buddy has a built th350 that has the 9" tail shaft he will sell me but I wasn't sure how it would fit. I will probably have to get a new driveshaft anyway once the 12 bolt gets added to the mix.

 

what are the advantages to using a th350 vs. a th400
besides price and availability? isnt the th400 way stronger?

just curiuos, i know nothing of this swap

Chris

 

To my knowlege the 400 is stronger, but takes more power to turn.

 

9" tailshaft will work but, I think its a "mid-length" tailshaft. There is a 6", 9", and a 12" tailshaft TH350's out there.

 

It's the 9" tailshaft version.

I used the TH350 because it's 25 lb lighter than the TH400, it uses a conventional driveshaft (not slip yoke), and it requires less power to turn.

The TH350, with the $300 billet sprag assembly, is as strong as a TH400.

Mike

 

yeah i was thinking of going to a TH400 when i get the big block
but it's much heavier than a TH700R4 or TH350 and i like having the use of OD

i think it would take a little more than just adding a billet sprag assembly to a TH350 to make it as strong as a TH400

 

Additional info:

Grind some metal off of the B&M torque arm mount to allow you to fit a socket on the top tail housing bolt. This will make removal 100X easier. In fact, I'd recommend the Hurst adapter. It's about $15 more, but it looks more complete and, from the picture, looks like it might fit better.

Also, if you use the speedometer calculator in TunerCAT, it will enter INCORRECT values. You can use that as a starting point and adjust the "Speedometer Scalar Fraction" until you get it perfect.

Mike

 

Do you have links for any or all parts

 

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