I saw this in Jeg's, it looks pretty interesting. Talked to a mechanic friend and he says this gear set was used in big RVs from the factory. In my (so far) limited research, all I can find is straight cut vs. helical cut gears as the difference between heavy duty and regular planetary gear sets, no mention of gear ratios.

http://www.tciauto.com/components/lo..._planetary.htm

I would just as soon use OEM heavy duty RV rebuild parts in my trans, rather than spend twice as much to have brand name "hot rod" parts, so I'm trying to find info along this line......It's going slow doing the detective work by phone and foot, so I thought I'd throw out a line here as well. I would have thought this would be popular among hot rodders if it is for real, but hardly anyone I've talked to is familiar with it.

Any thoughts, ideas, whatever?

John

 

I have never heard of alternative gear ratios used in the TH400. The straight cut gears were used however, I have one sitting here.

The lower gear would be great when your using a sane rear gear ratio. With 3.55s and the stock TH400 gearing I can take 1st gear all the way to 60mph, which doesn't help my 60' too much, so a taller first gear would be beneficial.

 

can't remember, if you can still use the 34 element sprag, go for the RV units (if you can find them)
most vettes with enough hp can smoke the tires with the std low gear, so no need to spend the extra $$$; without enough hp, the gear spread would be too much i think (assuming 2.75:1 or lower) - better to change rear gear
if your setup needs it though, different story

 

My thoughts are to give me a little better hole shot while keeping my 3.08 rear end for top end cruise....These ratios are the same as the 200-4R, which many people seem happy with, just no overdrive.

 

Does not cure the real problem...still an automatic

 

Yeah, well, ya gotta work with what ya got to work with.

 

Fevre: That's not a problem. I am setting up a little turbo automatic, leave the line with full boost, AWD, see ya later manual.

 

Stick cars suck for drag racing. I will take an auto with a loose converter any day of a stick. I have nothing but problems with my LS1 6spd car when trying to drag race it.

 

I have a pair of THM-400s with the # 227500 gear-set (2.75/1.57/1:1 ratios ), which I run behind a 10.3:1 355" SBC, 8" converter, 4.11s, and 28" x 10" slicks on my '79 Z28:
I think the deeper-ratio helps the short-stroke motor off the line (RPM-drop wasn't bad, even-with a 10" converter ), and I've had no troubles with them (I switched transmissions after 3 seasons, just as a precaution ).

 

Thanks, Glen.