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th400 gearing question

sweetk30

sweetk30

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i am going to have a th400 built for my plow / play truck. i have a few extra bucks. i was looking at a lower 1st/2nd gear set. would it be worth the money for the extra low ratio.

and no i dont want a 700 for this truck. to darn wimpy. and a 4l80-e is the same ratios as th400 just overdrive.

and do any of you have good places to pick up a gear set cheep.
 
I think the low 1st is great idea for a TH400. It should work like changing your axle ratio one step deeper without paying the price at highway speeds.
 
The lo gear sets for the TH400 are nice but not cheap,I got lucky and found one on ebay a couple of months ago for about $170. but the cheapest I came up with was Jegs for $360. I think.
I built a 400 with it to use with a LoMax, it has a 2:75 first gear.This is the second one that Ive owned,the first came from A1 Automatic in Cali.and I paid $400 for it like 10years ago.
They also had the only 3:00 first gear set that I have ever heard of with a lower reverse gear too.That set was over $500. and may buy one someday!
I have there catalog and could post there phone and part #s if anyones interested,they dont sell online.
 
yeah, unless you score a craigslist or ebay find... I don't think "lower th400 1st gear" and "cheap" go in the same sentence. If you do find a way to do it cheap, let me know!!!

j
 
sweetk30 said:
to those who have done it. what it worth the hassle?
Click to expand...

The lo gear sets are not hard to install,your basically just replacing the stock planetary carrier with the new one.The hard part is shelling out the $$$ for something that arrives in a package smaller than a shoebox and no one will ever see it!

Its a good setup for a multi-use truck that needs low gearing and hi-way speeds.
Reading from A1s flyer the 2:75 1st gear set is 11% lower than stock so 4:10 gears in the axles would seem like 4:56 while in 1st and second gear.
The 3:00 1st gear set is 21% lower and has a 2:47 reverse ratio vs the stock 2:06,I could see this coming in handy for a crawler.

I first one that I bought years ago was used in a Blazer pick-up with a BBC that I used for dirt drags and street and I was very happy with it!

My dream set-up for my CUCV- 6.2 diesel/ 4L80 with lo gear set/4:88 axle ratio/39.5 IROCs radials;)
 
wayne said:
Please post up some more info on the 3.0 first gear.
Click to expand...

The price of A1s 3:00 lo gear set was $545. back in 97,I called them about 3months ago to get the latest catalog hoping that they had lo gear sets avaliable for the 4L80 now.

What I ended up with was the same catalog/price sheet from 97:confused:

I called them Wed. to inquire about the gears and the man to talk to is on vacation until Friday,I will post back when I find out if they are still avaliable for that price!
 
Yes do so. I know the planetaries swap out between the 400 and 4l80 but I would really go for a 500 3.0:1 set for my up and coming 4l80 swap.
 
MEK5 said:
The price of A1s 3:00 lo gear set was $545. back in 97,I called them about 3months ago to get the latest catalog hoping that they had lo gear sets avaliable for the 4L80 now.

What I ended up with was the same catalog/price sheet from 97:confused:

I called them Wed. to inquire about the gears and the man to talk to is on vacation until Friday,I will post back when I find out if they are still avaliable for that price!
Click to expand...

Yes, please. I am deffinately going to stay with a th400 and my trans will probably get rebuilt next spring.
 
OK I talked to A1 and got some bad news, the $545. 3:00 first gear sets are now....are you sitting down? $1,295.

They said that they had to improve on them since 97 because they were not durable enough by modifing stock parts and were wearing the pinion gears/pins out in the planetary carriers.They now are using new machined parts instead which should last like a stock type carrier would.

They market the low gear sets for heavy trucks that tow or RVs that need the gearing without needing to use real low axle gearing.These trucks see alot of highway miles plus the weight really put extra load on the pinions so they were wearing out in say 20-30,000 miles.

For what I use my truck for the old design wouldnt scare me at all,it took me 5 years to put 20,000miles on it and I drive it even less now.Guess its back to stiff axle gears and od trannies:frown1:
 
thats a lot of coin... cheaper to 3:1 your 203 or lomax your 205. Gear reduction should always happen as far down the drivetrain as possible, so its not like its a big deal really. If the lower th400 gear was cheap (ie $200 or something) I'd do it myself... but bah, its all good. :thumb:

j
 
Just think of a 3:1 4l80, 3:1 203 doubled to a 3:1 lomax, with something even like 4.10's....

110 aint bad for a slush box, with a 5000 dollar drivetrain.
 
there is such a thing as too much gearing though... all those 3:1s would probably result in an auto being strong enough to overcome your brakes... not good! I'm gonna try a stock geared th400, 2.01:1 np203, 1.96:1 np205 and 5.13 axle gears and see how that works before I do anything that will cost more money. ;)

j
 
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