Topic: Gears gears gears (Read 12791 times)

francisolya · « **on:** January 07, 2015, 01:23:31 PM »

My J20 is a 78/9 RHD originally auto(now manual T18) with 4.0 six cyl,I have been told the dif ratios are 4.88,I have not even driven it yet but previous owner said it was very low geared/slow,my aim is to fit a 6 bt and ZF s5 42 through 1:1 transfer,I figure I'm needing at least 3.5:1 diff ratios to keep this motor working at its best..MAX rpm of 2600 and max torq somewhere around 1800 but with plenty of grunt below this(5.9L)current axles are 60 rear and 44 front,look original but who knows,rear is full floating and both 8 stud... sooooooo question is how do I get from 4.88 to 3ish without soending a small fortune,I gather I need different carrier's also,I don't mind buying new RnP's but whole diffs get very expensive with shipping and duties..any suggestions ?can the carrier offset be modified,going to lower ratios I presume it's more difficult as material would have to be taken off the carrier or Gear as opposed to thicker gear or spacer other way round..anyway open to suggestions or if someone has carriers to sell or swap for mine

wildwood · « **Reply #1 on:** January 07, 2015, 04:21:44 PM »

Carrier break is 4.10 4.56 so you'll need a new carrier so not cheap.
Larger tyres will alter the gearing ....
At a guess factory 28" tyres on a jeep with 3.55 needs a 4.10 when going to 31" tyres so you could work it backwards from there.......

dieselj20 · « **Reply #2 on:** January 07, 2015, 05:44:18 PM »

Quote from: wildwood on January 07, 2015, 04:21:44 PM

Carrier break is 4.10 4.56 so you'll need a new carrier so not cheap.
Larger tyres will alter the gearing ....
At a guess factory 28" tyres on a jeep with 3.55 needs a 4.10 when going to 31" tyres so you could work it backwards from there.......

Quote from: francisolya on January 07, 2015, 01:23:31 PM

My J20 is a 78/9 RHD originally auto(now manual T18) with 4.0 six cyl,I have been told the dif ratios are 4.88,I have not even driven it yet but previous owner said it was very low geared/slow,my aim is to fit a 6 bt and ZF s5 42 through 1:1 transfer,I figure I'm needing at least 3.5:1 diff ratios to keep this motor working at its best..MAX rpm of 2600 and max torq somewhere around 1800 but with plenty of grunt below this(5.9L)current axles are 60 rear and 44 front,look original but who knows,rear is full floating and both 8 stud... sooooooo question is how do I get from 4.88 to 3ish without soending a small fortune,I gather I need different carrier's also,I don't mind buying new RnP's but whole diffs get very expensive with shipping and duties..any suggestions ?can the carrier offset be modified,going to lower ratios I presume it's more difficult as material would have to be taken off the carrier or Gear as opposed to thicker gear or spacer other way round..anyway open to suggestions or if someone has carriers to sell or swap for mine

what ratio is 5 gear

dieselj20 · « **Reply #3 on:** January 07, 2015, 06:40:30 PM »

Had a quick google for ratio seams to be .76 if you run 3.54 diffs 33 inch tyres 65 mph will be about 1800 rpm

Mike Pavelin · « **Reply #4 on:** January 07, 2015, 07:36:27 PM »

Fit taller tyres.

Dave69 · « **Reply #5 on:** January 07, 2015, 09:48:33 PM »

as Mike has implied, maybe the previous owner(s) had 35+ tyres fitted at some point

j33pky · « **Reply #6 on:** January 07, 2015, 10:00:10 PM »

I have a pair of axle 60 rear and 44hd front on 3.73ish.. Sounds like it's got original axles, if it had the 4.2 straight 6 in then it would have a 4.88 gears with a lsd in the rear. What size tyre you running?

dieselj20 · « **Reply #7 on:** January 07, 2015, 10:13:31 PM »

35 inch tyres 4.88 65 mph 2300 rpm

francisolya · « **Reply #8 on:** January 08, 2015, 03:11:13 AM »

Thanks for all the replies,wheels are original factory 16.5's with 235,75's (im almost sure ),lot of the problem lies in the non revvy nature of the 6 BT ,just checked my particular model and max Torque is at 1600..huge tyres would be fun but it has to be drivable and somewhat practical,were the FSJs fitted with different ratios for UK/Europe?like the japs fitting lockers ?our terrain considered more challenging?anyway no matter how I look at it I need new/different diffs,thanks for the research Diesel J,3.5's wouldnt be so bad at 1800rpm/65mph on 33's,35's would help a little more,my first plan was to stick different axles under but when I started to research I found ppl struggling with gearing on the same eng/box combo and with 4.1:1 the lowest in my first option it's a no brainer to stick with originals and hunt for gears etc

j33pky · « **Reply #9 on:** January 08, 2015, 07:25:00 AM »

Sounds like you need to be ringing up someone and ordering some gears and carriers them! Is there a firm in Ireland that ships from the USA?

j33pky · « **Reply #10 on:** January 08, 2015, 07:29:36 AM »

Quote from: dieselj20 on January 07, 2015, 10:13:31 PM

35 inch tyres 4.88 65 mph 2300 rpm

That's what I will be running on mine!

JamesH · « **Reply #11 on:** January 08, 2015, 07:30:04 AM »

A 44/60 combo with 4.88 gears would sell for good money to an off-roader and might give enough to buy a set with 3.x gears and have cash left over. The downside is the axles won't be freshly rebuilt.

j33pky · « **Reply #12 on:** January 08, 2015, 07:31:19 AM »

When are we going to see some pics of your j20 Fran? What's the body like?

Bulldog67 · « **Reply #13 on:** January 08, 2015, 07:32:46 AM »

J33KY - nab his 4.88 please for spares so I can use them in your J20 when I buy it

Shame the d44 is different as there are some 4.10s in the parts mountain from when i went to 4.88. Im running 4.88 with 35s on a FSJ and it feels close to stock

JamesH · « **Reply #14 on:** January 08, 2015, 07:35:59 AM »

The extra gearing is good to help with extra weight of mods too, I run 4.88 and 35s on my XJ and although a bit more revvy it's good. I know the 6BT isn't going to want to be at 2200 all the time for cruising though.

j33pky · « **Reply #15 on:** January 08, 2015, 07:39:20 AM »

My j20 already has 4.88 with a lsd in the 60 pal... That's why I'm going to run 35" rubber.. I've got some 4.10 gears and carriers but it sounds like he want to go higher to meet the requirements of his Cummins. What ratio is your ram wildwood?

dieselj20 · « **Reply #16 on:** January 08, 2015, 08:27:30 AM »

My j20 is running 4.88 d60 front d70 rear five speed trans .89 overdrive plus a gkn overdrive .72 2000 rpm at 65mph 33 inch tyres max torque on my engine is at 2400 rpm

j33pky · « **Reply #17 on:** January 08, 2015, 08:53:35 AM »

D70 rear... Ooohhhhhh

dieselj20 · « **Reply #18 on:** January 08, 2015, 09:04:33 AM »

narrowed d70 from a cj10 tug

j33pky · « **Reply #19 on:** January 08, 2015, 09:11:34 AM »

What diesel you running?

wildwood · « **Reply #20 on:** January 08, 2015, 10:18:29 AM »

My Cummins 12 V has a Dana 80 and 3.55 gears behind a 4 speed auto 70mph is about 2250
Towing at 60 mph is about 1900 - 2000

Option was also a 4.10 rear end but was for the the NV4500. 5 speed manual.

Cummins seem to give their best at low revs and like to tug against something......

francisolya · « **Reply #21 on:** January 08, 2015, 10:25:44 AM »

Body's not great pky,looks like you've been busy with your body!looks nice,I've not had much time to go through it properly but cab is worst,A pillars are gone,floor is good as gone,tub is ok,looks like it's had a new floor recently but bubbling along the joint at base of floor,all but the A pillars will be relatively easy repair(relative to what I'm not sure lol)I hope to get all mechanicals sorted before body...there's SFA here when it comes to these kinda parts and even less for Jeep stuff,I'll have to source and import everything myself,there are a few 3.54's on ebay usa,Also be happy just to swap what I have for 3's..I have to get the finger out and get some pics of this heap posted,maby someone will recognise it and have some history

Bubba · « **Reply #22 on:** January 08, 2015, 10:30:11 AM »

i think j20 is running a 6pot yota engine and is uber nice

j33pky · « **Reply #23 on:** January 08, 2015, 11:56:35 AM »

The body works a pain.. I've been lucky I've only had to buy 2 trucks and a 4dr cherry to build mine but still needed a lot of welding.. Did buy some wings and a tailgate a bit ago but parts are scarce.

wildwood · « **Reply #24 on:** January 08, 2015, 01:30:57 PM »

Ah ha you have the same Scheppach wood planer as me

And am I guessing your truck and woodwork share the same space........

I spend more seat time in the 1 tonne reversing in and out than I do offroading

Author Topic: Gears gears gears (Read 12791 times)

francisolya

dieselj20

dieselj20

Mike Pavelin

j33pky

dieselj20

francisolya

j33pky

j33pky

j33pky

j33pky

dieselj20

j33pky

dieselj20

j33pky

francisolya

j33pky