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FJ20t gear ratios


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#21 Xnke

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Posted 22 June 2013 - 04:00 PM

Look for a later C-box...little more work to get together, but much stronger.

1995+ FS5W71C gearboxes are much improved strengthwise versus the older FS5W71B units. They are still just a front case swap away...and don't use the small countershaft bearing if you are concerned with strength. Of the fifteen damaged boxes I've had apart in my shop in the last two years, I have never found a box with severe gear tooth damage, without finding either the front countershaft bearing failed, or the pilot shaft bearing failed. The later boxes have a bigger pilot shaft bearing, as well as the 62mm countershaft bearing, 20+mm wide gears (the box in my garage is 22mm wide, except the input shaft and the 1st gear set being 24mm wide.)

#22 peter mc

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Posted 22 June 2013 - 06:40 PM

HAHAH man we smash 5th gear all the time on them at PI , the gear splits in 3 bits , i think Gordo has done it 3 times , thats why we have been using the fj20t box , runing 300+hp engines at 7500 for the hole time down the strate at PI in 5 gear  just kills the standard gox and gears . the cheepest setup is a turbo box with your bellhousing on it , then save up for a close ratio set so it stays in the torque all the time

#23 dat2kman

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Posted 22 June 2013 - 06:57 PM

So whats stronger, got bigger mainshaft, thicker gears, more supported selectors, better synchro setup.
Fj20det 71 B type overdrive fifth
Or
Sr20det 71 C tupe/rb20det 71 Ctype overdrive fifth.

#24 peter mc

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Posted 22 June 2013 - 10:19 PM

same gear strenth ,  with a gear set there up for about 330ftlb  stock around 290 yes they will take more , but its only a time thing , blokes smash SR boxes with ease with a stock motor .

the stock L box will be up for about 220ftlb at 240 its only time

#25 Xnke

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Posted 23 June 2013 - 07:58 AM

Yes, you'll smash 5th gear in ANY of those transmissions, including the FJ turbo box, at the power levels you're looking at. They're only 16mm wide in most of the boxes and 18mm wide in any of the rest I've ever seen...Just get a pair of 5th gears machined to fit the later box, if you can work around the ratios. I don't drive 7500RPM in 5th gear, because I know the C-box stock 5th gears won't handle it. They just don't look very strong compared to the rest of the gears. I have a metal shaper setup for cutting gears and internal splines on, but it's not working just yet and I haven't had time to futz about with it. I'd like to machine a 22mm wide 5th gear set  for these boxes from 4140-prehard or 9130 and deep-case them. I bet that'd fix 5th at PI, Peter!

The 1995+ transmissions run a strong roller bearing on the rear countershaft plus the tailshaft ball bearing up top, and the later boxes have much stronger-looking support in the case for both of those rear bearings. If I hadn't just sealed up the one in the shop floor I'd take some comparison shots for you. I am still trying to find a 24mm wide countershaft gear instead of the 22mm wide one I have, to match the input shaft gear in the box I've got built for my car; but so far, no luck. That would leave me with a 24mm input set, 1st gear set, 22mm 2nd gear, 3rd gear, and an 18mm fine-mesh 5th gear. There is plenty of room to machine a 22mm wide 5th gear set in any ratio you want, and not have to buy the whole countershaft assembly.

Gear damage on 1-4 is almost always bearing failure first, and I've heard of shift-fork breakage causing it to get locked into two gears at once, too, but haven't seen it. Usually broken forks just lock up the trans in one gear, but if you try hard enough...

Might want to look into just machining a replacement the 5th gear set, might be a more accessable option. Not sure if you can deal with the ratios you all got in the Southlands compared to what came here; most of the heavy-duty 95+ -C and -E type boxes here are from heavier box trucks and SUV's, and have close-ish ratio sets and 4.08 and 4.375 rear end gears, with a VG30e or KA24DE in front of them. The VG33ER-equipped SUV's and pickups had 3.321, 1.912, 1.517, 1.00, and 0.745 gearing, the VG30E boxes have 3.321, 1.902, 1.308, 1.00, 0.745 gearing.

Those SUV's aren't real common with those drivelines though, they usually have the FS5R30A and a VG30DE or VQ series engines nowadays.

The box in my floor actually came from a 1998 2WD Frontier SE, VG33ER engine and a 4.08 C233 solid rear axle. I'm hoping the odd ratio for 3rd gear was chosen for supercharger service, since that's what I'll be using it for.

EDIT: You guys are hitting 165++ on PI? (7000RPM, 0.833 5th gear, 245-45-17's on a 3.90 rear end)

#26 peter mc

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Posted 23 June 2013 - 09:00 AM

Most of the fast cars run a 4.1 or 4.3 top speed is 144 mph  .the track is all about corner speed and you need the short diff to get off the tight stuff

#27 dat2kman

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Posted 23 June 2013 - 09:50 AM

Xnke, we have a commercial machine shop here that does a .889 fifth gear, but it is at standard width, and they only do small batch runs, when they can fit them in.
If you were to produce some wider, and closer to 1.0 fourth fifth gear pairs, at a better tooth count than the horrid 0.752 or the not so bad 0.832, i am sure there would be a few down this way interested in purchading!

The Sylvia/180sx/200sx model that was a JDM car that many were private imported to Australa, had the C type boxes with a 0.832 fifth.
The larger six cylinder engined, both in line and V config motors, ie rb, vg/vq using the C type box, had the 0.752 fifth, ( great for economy!)

I'd be interested in obtaining a qty of fifth gear sets, rather than sending individual sets over time.
I have been converting a number of both B and C types to close ratio sets, and have found that the C types are quite superior to the B box, including the fjturbo box ( DR30 model)
Jason

#28 peter mc

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Posted 24 June 2013 - 01:54 PM

5th gear is a 18mm gear and does not have oil holes in it and does live at the hp and torque we make , thats why we all use it , the stock L box has a 16mm 5th with oil holes and when the gear fails it cracks from the oil holes out the gear falls in 3 bits, the fjt box does not have the oil holes

#29 Xnke

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Posted 25 June 2013 - 08:16 AM

AH, so now I understand. I thought you were breaking the 18mm gears!

So what makes the FJ box so desirable over any of the other standard, probably more common FS5W71C/E/G transmissions?

Is it just the gear ratios plus the undrilled 18mm 5th?

#30 NZeder

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Posted 25 June 2013 - 09:03 AM

The only advantage I see is it bolts in where the old B box is with no cross member changes but you get a box with a better 5th gear design and wider gearset. Once you have the FJ box installing the Kameari gearset gives you a good strong close ratio box with a good 5th. Having said that we have seen 5th gear still fly to bits in the 71C boxes = changing gear while over a bump/car unloaded = too much loading on the gear = bye bye 5th.



#31 Xnke

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Posted 25 June 2013 - 11:32 AM

I see. Being as 5th is trapped between the steel centerplate and the tailshaft/countershaft rear bearings, I see no reason for it to fail once we have the actual gear strength up high enough to prevent the gear splitting.

There is a local shop that can cut me a helical gearset (stronger, quieter) and I will be calling them up to see what they'd have to have to do the job.

#32 Riceburner

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Posted 25 June 2013 - 11:43 AM

I'm going to tear down my RB20det box this weekend and asses the condition, if it's repairable I might look into a CR set. Kameari seem the least expensive.

Can anyone make sense of the link? http://www.rhdjapan....4-r31-r32-58307

It looks like the super close Kameari gear set has a fifth of .759  ??? That's crap! I can see a few
Other sets listed, the top Silvia Q seems to have the best ratios, but is that compatible with the RB20det box? Then how do you specify which set you want?

#33 d3c0y

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Posted 25 June 2013 - 12:31 PM

That's because it's the stock 5th gear for the box. Kameari gear set is 1st 2nd 3rd and counter shaft (4th 1:1)


This makes it more clear:
[size=78%]http://kameariusa.com/L6_Gearset.php[/size]


FJ20ET boxes are easier to fit and have the 5th ratio you are after.

#34 NZeder

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Posted 25 June 2013 - 01:21 PM

I see. Being as 5th is trapped between the steel centerplate and the tailshaft/countershaft rear bearings, I see no reason for it to fail once we have the actual gear strength up high enough to prevent the gear splitting.

There is a local shop that can cut me a helical gearset (stronger, quieter) and I will be calling them up to see what they'd have to have to do the job.

Yes as that was the fix. A custom 5th (it is noisy) in the ratio required - I think 0.88, that and making sure the rear nut can't back off which is the common issue causing 5th to slide up and down a bit and smash its self to bits too. One common fix is replace the penned nut for 2 thinner nuts that tighten down on each other.

It looks like the super close Kameari gear set has a fifth of .759  ??? That's crap!

As pointed out - only a 1-3 gear set 4th and 5th are not changed so you are stuck with what the box has and most 71C boxes that is a crap 0.759 - unless you get the 0.83 5th from a NA RB20 box IIRC - or just go custom 5th that is stronger and the ratio you want/need.

#35 Riceburner

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Posted 25 June 2013 - 07:16 PM

Ah didn't realize it was only 1,2,3. First gear is pretty much useless on track and no issue on road, the other RB20det ratios don't look bad except fifth. If the RB box looks ok I might just look at getting a fifth second hand or from Albins.

RB20det ratio's Transmission 5 speed manual     
Gear Ratios
1 3.321
2 1.902
3 1.308
4 1.000
5 0.759
Reverse 3.636

Kameari L6 CR  L6
(FS5W71B)
1 2.624
2 1.814
3 1.360
4 1.000
5 0.813~0.933

Interesting that Kameari usa are over $500 more than RHD Japan!

#36 d3c0y

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Posted 25 June 2013 - 08:00 PM

Although the ratios dont look that different, throw them into gear calc and see the speeds you will be doing in each gear. You also need to see the change in RPM after each gear shift.


If you dont want to spend a lot of money wouldn't an FJ20ET box be the easiest options since it has the strong gears, the 5th gear ratio you want and bolts in?

#37 Riceburner

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Posted 26 June 2013 - 03:40 PM

I have an RB20det box in the shed. I also have a modified bellhousing i got for $20. It looks like $600 would get me a known good condition FJ box which would probably need bearings, maybe more. I believe the RB20det boxes are meant to have double syncros on second and third which the FJ doesn't, it's also a newer box so hopefully not as many miles on those syncros.

I think with either box ill end up at about the same cost. I'll have a better idea of which box i go for after the weekend.

#38 dat2kman

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Posted 26 June 2013 - 07:00 PM

The figures quated above for Kameari ratios will alter, depending in input drive/driven ratios.
First can be either 2.6 or 2.4.
The boxes i do are the 2.4 first gear.

#39 Riceburner

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Posted 27 June 2013 - 07:13 PM

So far so good with the RB box, except the centre counter shaft bearing has cried enough, ball bearings falling out everywhere. Gears & other stuff looks ok.

I can't get the main shaft & bearing out of the sand which plate, any ideas? Do you need a hydraulic press?

Also where do you get a rebuild kit for these boxes?

#40 Riceburner

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Posted 28 June 2013 - 08:22 PM

Bearing came out, I just needed an extra set of hands on the pullers and muchos grunt to get the fifth gear syncro hub moving on the shaft.

All pulled down. I'll need to get the Lseries bellhousing plunge cut 2mm, bearings, syncros, fifth gear, seals, main/counter shaft nuts. Possibly a CR set.

A few things (see pics), I noticed some funny colors on the syncro hubs.... Could it be oxidising from the failed bearing? Also the reverse counter gear has some decent chips on the edge is it still usable?

PPG/Pfitzner offer gearsets but they state on the website no warranty unless the sandwhich plate is modified to stop oil starvation on sr20 which is the same as rb20, is this a worthwhile mod (see pic)? I have it out so it's easy to do.

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