Does anybody know anything about the 3:1 first, 1.57:1 second aftermarket planetaries made for the TH400? I've seen reference to them in a couple different places, but I've searched all over and the only place I've found them for sale is here (at the very bottom of the page):

http://www.mikestransmission.com/catalog4.html

They don't have any pics or any other info, and I'm wondering who actually makes them and if anybody else sells them. If anybody is running these, where did you get them and what do you think? They are almost $1000 so they are not in the cards for me now, but I'm thinking they might be good for a DD. They'd offer more gear down low where it's needed, but still allow reasonable cruise RPM on the highway. I've got enough motor and gear that I'm not too worried about the widened gear spread, but I wouldn't mind hearing opinions on that either.

X2!

I'm interested too!!

heres one place:
http://www.crttransmissions.com/Components.html

2:48 stock vs the 3:10 for $695 .. I'd like to hear from the people that have this as well..

I've installed a couple sets that were purchased from A-1. Made a noticeable difference. IIRC they sold 2.75 and a 3.0 low gear kits. Its been awhile since they were installed but they are still running around.

Gus

What about converters that could do the same thing if you had one with a different stall speed than stock, built for wheeling?? Dont know if it would save you much money, but its a thought. The gear sets do look tits!!

What about converters that could do the same thing if you had one with a different stall speed than stock, built for wheeling?? Dont know if it would save you much money, but its a thought. The gear sets do look tits!!

the term stall speed is wholly mis understood.

you could only do this with a switch pitch converter. the switch pitch converter is a lockup design that allows about a 2500 rpm stall speed in a 4500 lb vehicle with 3.23 gears and 27 inch tires with the push of a button. the converter would again tighten up after the engine reached cruise rpm. it was set up for a car. only meant to be used at a stop, the switch pitch allowed the heavier cars to have a bit more slip through the converter until the unit got up to speed. If you had one, you could use it to drag race, if you knew how to work it just right.

the problem with a switch pitch converter is longevity. they dont last to long.

They were manufactured between 1965 and 1968/9 for use in Buick/Olds/Pontiac/Cadillac cars. they are literally as rare as hens teeth.

the lower first gear allows much more in the way of options. I would be interested too, as it would be nice to see what the 3.0 gears would do with my racer.

heres one place:
http://www.crttransmissions.com/Components.html

Well alright; $625 is getting a little closer to doable.

I've installed a couple sets that were purchased from A-1. Made a noticeable difference. IIRC they sold 2.75 and a 3.0 low gear kits. Its been awhile since they were installed but they are still running around.

Do you have a link for these? I searched A-1 and all I could find were a bunch of individual tranny shops.

Does anybody know who actually makes them and how they're made? I've seen pics of the 2.75:1 gears, and they are partially modified via welding. I would have to have an awful lot of confidence in the man doing the welding to trust it in this application...

Stall speed and stall ratio are two different things that get confused at times. A higher stall speed allows the engine to move make more power at stall. Stall ratio is the amount of torque multiplication produced by the torque converter, in effect different gear ratios within the torque converter. Allison lists the ratio for different converters that are used with the same transmission.

Gus

I have the TCI 227500 GM TH400 (2.75 1st, 1.57 2nd) it was about $450 when I bought it works great put 50k on it never had a problem. Here's a link to the TCI th400 page:

http://www.tciauto.com/Products/GM/gm_turbo_hydramatic_400.asp

I have the TCI 227500 GM TH400 (2.75 1st, 1.57 2nd) it was about $450 when I bought it works great put 50k on it never had a problem. Here's a link to the TCI th400 page:

http://www.tciauto.com/Products/GM/gm_turbo_hydramatic_400.asp

Is the increased grunt in low/second noticable/worth it? What do you think of the gear spread/RPM drop between gears? Do you remember if your gears came with a modified sun gear or do they use the stocker?

Drive a 700r4 to check if you think the gear spread is going to bother you.

Drive a 700r4 to check if you think the gear spread is going to bother you.

True, the 700r4 has an even greater gear spread. I'm really not worried about it, just interested in driving impressions.

Ive been told that the strait cut planetaries have a lower ration then the helical cut planetaries can any body verify this. If its true then this would be a cheaper alternative than buying aftermarket. Just a thought

Is the increased grunt in low/second noticable/worth it? What do you think of the gear spread/RPM drop between gears? Do you remember if your gears came with a modified sun gear or do they use the stocker?

I think it was definitely worth it.I noticed a difference right away. the stock gears would barely get it out of its own way. if i was gonna drive it on the street I don't think i would go too much lower cause then you would shift allot quicker. I think that it was just right shifting through the gears. I do believe it did come with a new planetary

Ive been told that the strait cut planetaries have a lower ration then the helical cut planetaries can any body verify this. If its true then this would be a cheaper alternative than buying aftermarket. Just a thought

they are much weaker and will wine very loud so thats two reasons enough for me to stay away.

they are much weaker and will wine very loud so thats two reasons enough for me to stay away.

lmfao!

ok, no.

the straight cut planets are not weaker.
they do not whine too loud, either.

straight cut planetary gears were designed to remove the thrust loading from the sun gear as it carries a load on acceleration. in stock form, the helical cut gears for the planets and sun gears place a small load on a torrington bearing. when the manufacturer found that these torrington bearings were failing due to heavy loads *(generally loads above 15k lbs), they found that they could alleviate the issue with a straight cut gear at the cost of a minor whine.

and no, they dont make a 3.0 ratio straight cut gearset.

and the straight cut gears are only available in a 2.48 ratio.

straight cut planetary gears were designed to remove the thrust loading from the sun gear as it carries a load on acceleration. in stock form, the helical cut gears for the planets and sun gears place a small load on a torrington bearing. when the manufacturer found that these torrington bearings were failing due to heavy loads *(generally loads above 15k lbs), they found that they could alleviate the issue with a straight cut gear at the cost of a minor whine.


Yup. That's why they were installed in TH475s which came in high GVW applications such as busses. I don't know what all they came in, but to my knowledge, they never came in 1-ton or under trucks. Somebody correct me if I'm wrong. Like Grumpy said, the straight cut gears are inherently stronger and run cooler due to the lack of thrust loading. I can't speak about the whine since I've never even seen a TH475, let alone heard one run. I think you'd have to have a pretty radical or heavy rig to necessitate the straight-cut planetaries though.

I think it was definitely worth it.I noticed a difference right away. the stock gears would barely get it out of its own way. if i was gonna drive it on the street I don't think i would go too much lower cause then you would shift allot quicker. I think that it was just right shifting through the gears. I do believe it did come with a new planetary


Just to put it into perspective for my setup, what axle gearing and tire size are you running?

Just to put it into perspective for my setup, what axle gearing and tire size are you running?


37 inch MTr s on the street and 37 bfg krawlers off road. 4.88 ratio

One last bump for anybody with new info.


37 inch MTr s on the street and 37 bfg krawlers off road. 4.88 ratio


I'm running 4.56s w/35s right now, and I'd like to go to 38s when these wear out. When I regeared the axles, I never planned on going larger than 35s (:shaking:), and I'm concerned 38s would be a little tall for the 4.56s. The 3:1 first would more than make up for the taller tire on take off and while crawling, plus let me have a decent cruise RPM. It would be a little more expensive than regearing the axles, but it would be less work and time (or at least less trial and error dicking around...) and I think it would give better results.

I'd just like to know exactly what I'm getting for my 6 bills before I lay 'em down. I'm surprised more companies do not offer these, but I can't seem to find shit about them other than the two links given above.

the th400 doesnt use 16% of the power going through it to run it through the gears.

it uses that power to spin the 33 lbs of rotating weight.

you wont get mileage back by doing the 3:1 swap.
you wont get much of anything, except a different gear split.
sure, the 400 will make the engine work harder to get to speed.

its a proven fact that the stock gears have worked for YEARS with the same ratio.

this is what we know.

I havent seen/run 3:1 stuff. I cant make a determination on it until i get a set in my hands.
I would call A-1 and ask them what method they used for gear reduction prior to purchase. What did the gears come out of? (were they like the 2.75 gearset, coming out of a 200r4?)

thats info you can use.

the th400 doesnt use 16% of the power going through it to run it through the gears.

it uses that power to spin the 33 lbs of rotating weight.

you wont get mileage back by doing the 3:1 swap.
you wont get much of anything, except a different gear split.
sure, the 400 will make the engine work harder to get to speed.

I understand all this. I never said the TH400 eats power through the gearing or extra drag (I actually never brought it up at all). I realize it eats power by forcing the engine to accelerate heavy parts. The TH400 design is particularly bad in that respect (direct drum), but I see no reason why it would have much more drag than any other basically similar auto.

I am not expecting or looking for an improvement in mileage with this. That is not at all my goal. Mainly, I would like to keep my gearing the same or lower it a bit. The larger tires will move me in the opposite direction. However, I have already regeared the axles, and don't really want to do it again since I've got new parts in there, and took the time to get a perfect pattern on the gears. The 3:1 would actually give me a lower overall ratio even with the tires, and a wider gear spread which I think is more versatile. The TH400 has a pretty tight spread stock which is one thing I don't like about it.

Sure, I would like to keep the cruise RPMs down if I can w/o affecting low speed performance just because there is no point to spinning the motor any faster on the highway. Do I think it will help the mileage? Probably. Will it be a noticeable improvement? No. Certainly not at the small difference we're talking here, and probably not even with a full OD gear. I'm actually running an NV4500 in it now, and after I did the swap I did get a small but noticeable improvement in mileage (I was on 33s at the time), but it could have been partially due to the inherently more efficient manual as much as the OD gear. I don't know, but I do know there is nothing that will ever make these trucks fuel efficient considering the weight, rotating mass, and aerodynamics. If you want that, get a 'Yota. Or better yet, a different pastime. However, this thing is my DD and it gets old screaming at your passenger and listening to the damn thing turn 4000 RPM going down the interstate, and it's unnecessary. It is infinitely more pleasant to drive with the OD. If it was a trail toy, naturally I wouldn't care but when you've got to do the daily commute in your rig, it is a legitimate irritation worth addressing if possible.

With that said, this truck is creeping more and more toward being kind of a "weekend vehicle," which is why I'm considering the swap back to a non-OD auto. The stick is great on the street, and I'm plenty capable with it offroad (this truck was actually my 1st and only automatic 4WD), but there are things I miss about running an auto on the trail, and the wind-up from the Detroit is a PITA.

As to the proven status of the factory planetaries, you'll get no argument here. And if the 3:1 gears are built like 75% of aftermarket shit, they would just be a waste of Chinese steel. Which is why I'd like to get some more info about them if anybody has it. If not, I'll have to call around if and when I get ready to actually do this. It will be a while.

Then again, maybe I should just forget dicking around with this shit and just bolt in the trans that comes stock with a wide gear-spread AND overdrive.












:flipoff2:

What did the gears come out of? (were they like the 2.75 gearset, coming out of a 200r4?)

:eek:

I must have missed this the first time. Are you sure about that?? I hadn't thought about it before, but I guess they do have the same ratios (I've always read 2.74 for the 200-4r but I guess it's close enough for gov't work). I can't remember where, but I saw a pic of the 2.75 gears once, and there was a larger dia. but smaller width gear welded to the stock sun gear which I thought that was mighty funny. It might make sense if they just use the the stock 200-4r planet/carrier assembly. That's not really the kind of "upgrade" I had in mind...

A-1 says they have good stuff, you might call them and ask them to fax you an info sheet on the 2.75 stuff.

and you might also ask their opinion about the 3:1 stuff.

A-1 says they have good stuff, you might call them and ask them to fax you an info sheet on the 2.75 stuff.

and you might also ask their opinion about the 3:1 stuff.


Yeah, I definitely want to find out more about it before I get too excited. I'll call around if I ever get to the point of seriously considering this. Hell, I haven't even got a TH400 yet, so it'll be a while.

Anyone have any other sources for the 3:1 gearset and would it be a good choice in an AMC housing behind a 2000 4.0L TJ.

Wow 2 year old thread! Anyways, I don't think the 3-1s are available anymore. I bought a 2.75 set from Art Carr years ago for one of my tow trucks