TheSamba.com :: View topic - Trans rebuild Questions 4.57 Vs. stock 4.86 R&P

Mon Oct 22, 2018 3:24 pm

Iv searched in this n got nothing.

Going to get a rebuilt trans from GW with a tbd.
thinking of going up to a 4.57 ring and pinion. I have a stock 2.1

Is this too high for a stock motor? Tire size is 215/55/17

Mon Oct 22, 2018 3:33 pm

It will probably go down the highway fine. On hills where you used to downshift to 3rd it will not change much. Moving off from a dead stop up a hill you will notice it some. Where you may not like it is on the highway on a long up hill grind. Where you could always pull 4 th you may be downshifting more often. When the engine gives up the ghost, you will be better geared for more
power.

Mon Oct 22, 2018 3:45 pm

If you don’t have the time or will to add letters to the words of your questions to make legibility, why would this great community lift a finger? Some members are ESL and being one I ask you to spell check out side of this forum.

Mon Oct 22, 2018 4:06 pm

MarkWard wrote: It will probably go down the highway fine. On hills where you used to downshift to 3rd it will not change much. Moving off from a dead stop up a hill you will notice it some. Where you may not like it is on the highway on a long up hill grind. Where you could always pull 4 th you may be downshifting more often. When the engine gives up the ghost, you will be better geared for more
power.

Uphill from a dead stop- this is the part that has me debating the choice. Im ok with noticing it, as long as I can get going when I need to. I havent been in situation where I couldnt make up for lack of torque by coming into an obstacle with more speed.

Thanks for the feedback

Mon Oct 22, 2018 4:26 pm

You've already increased tire diameter by an inch and a half .. Going from 4.86 to 4.57 you'll likely find yourself slipping the clutch more on hill starts.

Mon Oct 22, 2018 7:24 pm

Not sure what you think this will achieve, but will presume it's to save revs and gas in top gear.

While that's a benefit, it will also bog you down in every way except on the flat in 4th. If you had double the horsepower, it makes more sense but you cannot overcome the loss of acceleration this will give you. When rebuilding our tranny we went the opposite way, to a 5.43, and it was an awesome gain on dirt -- (and on pavement from 1st through 3rd, changed 4th from .85 to .78) -- by comparison to the 4.86, moving the 1st to 2nd shift point from 21 to about 18. I'd prefer 12-15 but it seems there's no simple way to do this, even in a 5-speed.

D-Rated tires can run 15 lbs. more pressure, and this is also a big help in pretending there's more horsepower, torque, and acceleration.

Possible Post-Killing Caveat: Not familiar with that tire size, what is the diameter???

By the way, if by "TBD" you mean a Peloquin, you will LOVE it.

Mon Oct 22, 2018 10:25 pm

You guys make this an even harder choice! Thanks for the input your a very helpful group. The transmition world is new to me and i have no reference beyond bicycles. Also thanks for co-signing my decision on the pelican. (Tbd) this is a lot of $$ for me. Tire size is almost 1.5 inches larger in diameter than stock as stated above. Transmition and power steering are the only syatems to refurbish till my van is "done"...

Mon Oct 22, 2018 11:00 pm

I don't see an actual diameter reference that might clarify advice you'll get... at least from myself and others not relating sizes to diameter.

If the tire is anywhere near 27" or above, you will lose a lot of noticeable revs and acceleration, compounded by the 4.57, the gist of my concern.

I spent a fair chunk of time when going to 16s, to calculate with the help of Arizona Transaxle and here, to not get this wrong. The 5.43 made the 27" BFGs quite bearable, a gain compared to the 25.6" fronts and 27" rears I was running.

The new van we just bought has 27s on 14" steelies, and we're putting the same 16x7.5 Eurowheels and BFG 215/65s on it, without the 5.43. I'd be really nervous doing this if not for the current steelies being quite heavy, but the idea is to do this in advance of a tranny rebuild we can't swing right now. There's simply no other D-Rated AT tires I know of that fit these 2WD vans in 14" and 15", hence the decision.

After running both C- and D-rated tires on rough roads over five years, and at GVWR on pavement, I will never run another C-rated tire again. Others will disagree, but in my view C-rated tires are yet another hazard on vans full of them already, and I like the safety and stability of stiffer sidewalls and tires with more air in them.

All to repeat, if you're sticking with a 2.1 and tires around 27"+, I absolutely *would not* do the ring and pinion change you're considering -- especially if you're doing much on dirt!

Tue Oct 23, 2018 5:27 am

I have a 2.5 Subie at 165 HP and have run a taller 3rd and 4th gear. I am back to stock gearing and happier. I did not like the loss of power climbing hills, especially when at higher altitudes. A 5 speed with a tall 5th gear and stock 4th would be just the ticket but it is not what I have to work with.

So my advice is to stick to stock transmission gearing, especially with a stock 2.1 wbx. You already have taller tires it sounds like.

Tue Oct 23, 2018 5:49 am

Bicycling should give you better insight into gearing than online ratio calculators etc. The load you feel in the wrong gear on a bike is the same feel the engine and drivetrain feel.

If the ring and pinion are in good condition, you save a lot
of labor just installing the torque bias differential. You only need to set the carrier bearing preload and the adjust the backlash to the spec you had before removing the carrier. I realize you are looking at an exchange unit, but updating yours could be a savings over a complete exchange unit especially if you are trying to save some coin.

Tue Oct 23, 2018 6:25 am

dobryan wrote: I have a 2.5 Subie at 165 HP and have run a taller 3rd and 4th gear. I am back to stock gearing and happier. I did not like the loss of power climbing hills, especially when at higher altitudes. A 5 speed with a tall 5th gear and stock 4th would be just the ticket but it is not what I have to work with.

So my advice is to stick to stock transmission gearing, especially with a stock 2.1 wbx. You already have taller tires it sounds like.
Interesting to hear that even double the bhp isn't enough.

I'd love a Fiver with a granny 1st, but same thing, "they" -- (Gunther and crew, et al) -- just didn't care what we wanted. Kraut-swilling bastages all, though truthfully they got the gearing right for everything but going 9, and 90.

Oh, the Inhumanity! :lol:

Okay, looked up your tire size and it's 26.3", smaller than I'd suspected.

So the question now is, do you want less rev/more speed per rev on the highway, or better climbing, and/or better climbing on backroads.

That is the consideration you should, Ahem, consider most of all. For me, I want hill-climbing but you may want faster highway speeds on the flat. But know that is the main scenario where changing the ring will benefit you, and in my view, faster highway speeds puts more strain on each and every drivetrain part (and I am personally not in a hurry). MPG gain will be nominal when dropping just a couple hundred revs if I'm calculating accurately. Inverse is also true if you don't care about dragging the engine down on hills a bit.

It all depends on what you're trying to achieve, if you're EVER likely to go to a taller-yet tire height, and I do recommend adding the South African splash plate and the mainshaft thrust plate, too.

Also highly recommend Arizona Transaxle as a great shop run by great people!

Good Luck, enjoy! 👍🏼