ok since i cant go flippy 300 im gonna go atlas..... i want to go 4.3 but several people brought it ito my attention that 4.3 is too low with an automatic......


heres my setup you guys tell me what you think so i can say fawk your opinoin hehehe :smokin:


97tj 4.0 auto trannnnnyyyy
4.56's 38.5 sx's
tranny is running a custom converter high performance parts and clutches, and a shift kit.

with 36's i had a decent crawl but i lost some of it with the 38's. im not going to put ANY money in the 231 so atlas is the way to go.

so what do you think 4.3 too low?

thanks guys :flipoff2:
lemmy know

is any ratio ever 'too deep'? I know it's recomended to use 3.8, but I don't know anybody who does...

I have heard the 4.3 will power right through the brakes. Don't know this first hand though.

beef up your brakes:flipoff2:

Works fine for me...sb400, TH350, Atlas 4.3, 38.5SX's but I have Disc brakes on all fours.

Jeeper

Why (in the case of an auto) would a 3.8 be any different than a 4.3. :confused:

OK sure your fluid will tend to over heat but wouldn't you have that same problem with the 3.8 anyway?

I don't run an auto.,but that is the only problem I could think of.

I would get the 4.3 and a good tranny cooler.:flipoff2:

Call advanced adapters,they (almost)always have good advice for my issues;)

Originally posted by Cutter
is any ratio ever 'too deep'?

Yes it can be. Get too deep with an auto and there will be NO way to stop...you will have to put it in nuetral every time you have to stop. :( I have heard a lot of people say go 3.8 with an auto.

hmmmm

is there anything WRONG with going 3.8

i dont wanna drop 2 grand or just about into an atlas then find i should have gone 4.3 cause its not low enough.


but i also dont wanna run into it being to low to deal with.

im running waggy brakes so i havent had many problems stopping, eventually i see going disk in the back but thatsdown the road.

I have a 3.8, t18, and 4.10's I am almost at 100:1 :rolleyes: I dont seem to have any problems with that ;)

hey keith.... do u know the equation to get your crawl ratio... ive wanted to look at that see where i am and where i will be see if its too much or too little?

ok i've never understood this either... mechanical advantage is mechanical advantage... and the brakes are at the receiving end of all those gears, not between.

3.77/4.27
4.33/3.73

both end up with the same ratios, so i don't see why you shouldn't take the 4.33 over the 3.77 if you want a bit better gearing and you've gone up in tires.

First gear times transfer case ratio times axle ratio. In my case...

6.32 x 3.8 x 4.1 = 98.4656

But crawl ratio doesnt necessarily tell you if your brakes can handle it or not. Bottom line, my ratio works great, but I plan to go to 4.88's for that extra depth ;)

well acording to the NUMBERS i have a SHITY crawl ratio cause im running that pesky ol automatic.

so right now im at
2.74 X 2.72 X 4.56=33.9848

which really the numbers suck but it doesnt seem bad in real life.

ok if i go 3.8......
2.74 X 3.8 X 4.56=47.4787
better... well acording to the number

now with a 4.3......
2.74 X 4.3 X 4.56=53.759


hmmmmm it still doesnt help me much but there is a significant drop from what im at now to an atlas. i guess ill have to look at percentages or something

When calculating your crawl ratio, you need to multiply your crawl ratio by 2~3 to get something equivalent to a manuals ratio. This is due to the torque multiplication in the converter. I forget what the exact # is. Probably different for various converters/tranny's.

Alan,
I don't know if it helps, but I either plan on getting a 4:1 for my t case, or doing a 300 flip with a 4:1 in that.. and Im running an auto, 4.56's and will have Q78's (35.5x11) swampers on the jeep..
Scott

Cochese that makes sense never thought of that.

im gonna swing by the tranny shop see if i can find out some info, maybe i can get the numbers.

scott..... let me know what happens, i keep missin ya on aim and playin tag on the boards.

Circle track racers will often run an auto tranny without a torque converter. They use a clutch pedal hooked to a valve that releases the pressure to the forward clutch inside the tranny. They only use this "clutch" when coming to a complete stop. Has anyone who is experiencing the overpowering the brakes scenario considered making a similar modification. (That is installing a clutch pedal not eliminating the torque convertor) I would think that would let you run as low of gears as you want without worrying about how to stop.

Originally posted by Cochese
When calculating your crawl ratio, you need to multiply your crawl ratio by 2~3 to get something equivalent to a manuals ratio. This is due to the torque multiplication in the converter. I forget what the exact # is. Probably different for various converters/tranny's.

That's bogus - The overall gear ratio is the product of all of the ratios you have available in any given combination of transmission/transfer speeds - nothing more - nothing less. If you have a 2.5:1 transmission low, a 2:1 transfer low and a 4.5:1 axle ratio your overall gear ratio is 2.5 X 2.0 X 4.5 or 22.5:1

The advantage of a torque converter is the fact it roughly doubles the engine torque available to the transmission input shaft. It does not change your gear ratio.

Now for the theoretical shit . . . In a perfect loss-free world. Let's say you have an engine that develops 100 lb-ft of torque and applies it to your 4.5:1 axle. This effectively applies 4.5 X 100 lb-ft or 450 lb-ft of torque to your drive wheels. Now, factor in the 2:1 multiplication of the torque converter and you just hit 900 lb-ft of torque to the ground. Your brakes handle this with ease.

So you stuff your rig into low gear - low case (22.5:1) and the 900 lb-ft of torque becomes 4500 lb-ft of torque and your brakes are maybe OK but maybe not. Throw in another 4.0:1 reduction and you've probably exceeded the capability of a stock brake system in a rig with an automatic transmission.

The advantage of a torque converter is the fact it roughly doubles the engine torque available to the transmission input shaft.

I said that.

Let's say you have an engine that develops 100 lb-ft of torque and applies it to your 4.5:1 axle. This effectively applies 4.5 X 100 lb-ft or 450 lb-ft of torque to your drive wheels. Now, factor in the 2:1 multiplication of the torque converter and you just hit 900 lb-ft of torque to the ground.

I also said that (in less words), what is bogus? Put a multiple of 2 on your crawl ratio, and you will get the same torque multiplication result. The converter isn't a gear reduction, but a torque multiplication as much as the gear reduction is. I undersand that multiplying in the converter wont give you ACTUAL crawl ratio, but it is a good # to go by to compare it to manuals.