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Topic Review (Newest First)
09-06-2006 06:08 PM
Jeeper426 waow, i didnt realise that there was so much to a TH350 and TH400, i'll definately ask you guys before i do any mods involving a tranny seeing as i'm kinda' a Noob when it comes to transmissions, and i was looking in the wrong column when i typed that thanks for clearing that up for me
09-05-2006 10:34 PM
Crosley wow, what a group of information flying around.
09-04-2006 05:43 PM
jakeshoe Spline doesn't matter, it is the low planets that you use.

You would use the pinion gears from the 700 and have a custom sun gear made.

You have two sets of planets in the TH350 and TH400. The planets in a 700 are very similar to a TH350, basically the same design but with different gearing.

You would use the 700 pinions and output ring gear, but the sun gear would have to be half 700, half TH350.

You would also have to do some fancy work on the ring gear since the output shaft is attached differently in the TH350 and 700.

Disclaimer,
I haven't actually done this, as in made a set. I am going on what I was told by another trans guy who does make these setups using the parts mentioned and a lathe, welder, etc.
My info could be incorrect or incomplete.
09-04-2006 04:39 PM
runn141 id like to find out more on how to do that, ive rebuilt 350 turbo's before
09-04-2006 04:36 PM
runn141
Quote:
Originally Posted by jakeshoe
Crosley works at Hughes so I'm sure they make or market some different gearsets.
Kilgore is def an innovator in the TH400 world.

I like Chris at CKPerofrmance for his custom parts, although I haven't used any of the low gearsets for a 400 yet.

My understanding is that you use parts from the lower geared 700 or 4L60 planets to make the low (2.75) gearset for a TH350. You could also reverse this and make a shallower gearset for the 700, Chris makes a 2.66 first gear ratio for the 700 IIRC.
That would be a pretty good gearset in the 700.
does it matter what spline the 700r4 is 27 or 30? and wouldnt it be a 3.06 ratio? or is it some of the sun gears you change?
09-04-2006 04:33 PM
runn141 the planetary set for the 400 turbo lowers 2nd from 1.42 to 1.75 where the 350 turbo doesnt lower 2nd gear any.thats what i see at tci,
09-04-2006 04:29 PM
runn141
Quote:
Originally Posted by jakeshoe
Gentlemen,
The TH350 came with a 2.52 low gear ratio from GM stock, period.
The Th400 came with a 2.48 low gear ratio from GM stock, period.

There were never any other gear ratios offerred from GM. I rebuild these units and have multiple references to this including GM service manuals, ATSG tech manuals, as well as other reliable information, not including the hundreds of each unit I have personally rebuilt. There are several other very knowledgable transmission guys who frequent here who can confirm this.

There are aftermarket gearsets available for both the Th350 and TH400 to achieve a 2.75 ratio low gear. This requires a different pinion gear tooth count as well as a different sun gear tooth count.

The 700-R4 came with a 3.06 ratio first gear, some call it a 3.07 ratio. Again not the Th350 or 400.
everything jakeshoe said is it!
09-04-2006 04:17 PM
jakeshoe Crosley works at Hughes so I'm sure they make or market some different gearsets.
Kilgore is def an innovator in the TH400 world.

I like Chris at CKPerofrmance for his custom parts, although I haven't used any of the low gearsets for a 400 yet.

My understanding is that you use parts from the lower geared 700 or 4L60 planets to make the low (2.75) gearset for a TH350. You could also reverse this and make a shallower gearset for the 700, Chris makes a 2.66 first gear ratio for the 700 IIRC.
That would be a pretty good gearset in the 700.
09-04-2006 04:13 PM
hrodgmc John Kilgore is the man who usually is the first to design the different ratio planetaries. He makes a 2.75 and a 3.00 (1st gear) last time I spoke with him. You can get them for 600-650 straight from him or a reasonable custom tranny shop.
Crosley can probably get them for you.
09-04-2006 03:03 PM
runn141 the benefit of the low gear 2.75 is to get same 1st gear ratio from a 3.42 differential that you would from 3.73 with a stock 1st gear. and no, no 400 turbo came factory 2.75 first gear.
09-04-2006 02:42 PM
jakeshoe Gentlemen,
The TH350 came with a 2.52 low gear ratio from GM stock, period.
The Th400 came with a 2.48 low gear ratio from GM stock, period.

There were never any other gear ratios offerred from GM. I rebuild these units and have multiple references to this including GM service manuals, ATSG tech manuals, as well as other reliable information, not including the hundreds of each unit I have personally rebuilt. There are several other very knowledgable transmission guys who frequent here who can confirm this.

There are aftermarket gearsets available for both the Th350 and TH400 to achieve a 2.75 ratio low gear. This requires a different pinion gear tooth count as well as a different sun gear tooth count.

The 700-R4 came with a 3.06 ratio first gear, some call it a 3.07 ratio. Again not the Th350 or 400.
09-04-2006 01:09 PM
Jeeper426 i've read one of the GM performance Transmission Gear ratio books, and didnt the TH400 have a 3.08:1 first gear?
i checked with GM about the TH350 we built for my 4x4 and i learned it has a 3.07:1 first, and we did a Lockup Omition or something like that, so we could use a standard Non-Lockup Torque Converter
08-25-2006 11:21 PM
jakeshoe John,
I assure you there was never a 2.75 TH400 gearset. You can veryify my info from an ATSG manual, GM Service manual, HP Books by Ron Sessions, etc. it just did not happen.
I'm sure some of the other builders can verify this also.

I just sold a built up 200-4R. You're right, they aren't cheap. I started figuring the total parts it takes to build one, it adds up.
Billet forward drum- $420
Rebuild parts- ~$200
Valve body kit- $75
Servo- $100
oversize boost valves $30
etc..
If you use the desirable valve bodies or cores, add $250-600 to the cost.

I ran the 200-4R with 3.73's and it worked well, I would probably use a 4.10 if using it again.
08-25-2006 10:01 PM
JPhil Ah, well, it was a nice little dream while it lasted! That TCI unit is neato, but for that much money, I could do other stuff that would probably make more sense. Or apply it to my 200-4R.

Thanks,
John
08-25-2006 09:38 PM
jakeshoe John,
I assure you there was never a 2.75 TH400 gearset. You can veryify my info from an ATSG manual, GM Service manual, HP Books by Ron Sessions, etc. it just did not happen.
I'm sure some of the other builders can verify this also.

I just sold a built up 200-4R. You're right, they aren't cheap. I started figuring the total parts it takes to build one, it adds up.
Billet forward drum- $420
Rebuild parts- ~$200
Valve body kit- $75
Servo- $100
oversize boost valves $30
etc..
If you use the desirable valve bodies or cores, add $250-600 to the cost.

I ran the 200-4R with 3.73's and it worked well, I would probably use a 4.10 if using it again.
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