L28 Transmission Swap Options

[Whittie]

Well i've got a 260z and I've just finished fiddling with the engine on it and it's putting out 180hp, 240Nm of torque. As a bit of background - before the re-build i've not had ANY problems with gearboxes.

 

Just after the re-build, after about 100km of racing its starting to get hard to get into second gear. I take the box to the local Z expert (he is actually really quite good) and he puts r33 synchros in the box. After about 100km the box starts falling out of first gear under acceleration. Take it back to him and he re-does it. 100km later second gear starts falling out. The car is about to be shipped across the country for 3 race events and time is tight so he puts the gearbox from his car in it (same r33 syncros). After about 100km of racing in the three events third gear is getting notchy. Back to him it goes.

 

About 2/3 months later and third gear catastrophically fails at about 7000rpm on the track.

 

No big deal, these things happen. So it goes back to the guy who did the synchros and he replaces the shaft with third gear on it.

 

Fast forward a month or so and the car has done 1 event. About 60 laps or approx 100km of racing. Driving the car to an event, accelerating at about 30km/h in second gear and suddenly the rear wheels lock up. I get my foot on the clutch, pull over, and realise the engine is still running. I tried to put it in gear but it didn't want to know about any gear other than reverse. I take my foot off the clutch and the engine stalls without the car moving.

 

So, here I am. The car is sitting on a median strip in the middle of the road about a half hour walk from home (I timed it ) and whilst I wait for traffic to die down so I can safely collect it I've been doing some research into what i need to do about it. Obvisouly the 'ole 260z boxes just wont cut the mustard anymore and i need something stronger.

 

I've done some searching on the forum and found info on the Z32 swap, however the idea of purchasing a $1500 gearbox and then having to purchase a $1500 install kit from America (im in AUS) does not sound appealing.

 

Therefore, I am wanting to know what else is available that is a fairly standard straight swap. I'm going to get the 260 box repaired (and i aint paying for it, thats for sure!!) to get the car atleast moving again, but i need to do something about a new box ASAP.

 

Any info that anyone is willing to share about differant boxes and their ability to hold moderate power is most appreciated.

[skib]

try a search on the BW T5 5speed trans that came with the 280zx turbos

[ezzzzzzz]

The 240SX (KA) transmission swap is reasonable and has proven to be a strong contender behind some high hp cars over here. I'd look into that option.

[Xnke]

In Australia, the 240SX does not exist, as far as I know. Wasn't the KA engine a US only thing?

 

Try the following engined cars:

 

Anything POST '87 with CA18, CA20, RB20, KA24 (if you got that there) or possibly the SR, not sure if the SR trans is a FS5W71C or not. cars include the S12, S13, S14, Xterra, and some hardbody trucks. NOT a bolt in swap, as you'll be needing a L-series 5 speed front case, machine for the larger 16mm 1-2 shift rod, AND you'll need to machine for the larger 62 countershaft bearing, and provide clearance for the larger and thicker countershaft gear. IF you use an L-series 4 speed front case, you'll need to move the reverse switch forward 22mm. Also, you'll need to shorten the driveshaft 50mm, and remove the dust collar from the shaft. Move the transmission mount back about 50mm as well, but measure to be sure as every car is a little different.

 

Also, the Z31 not-turbo trans will work from '84 and up, but mid-'86 they got a double cone syncro on 2nd gear, so '87 and newer are preffered. New from nissan, the FS5W71C is 1540$, plus maybe 120$ of machine work for the L-series bellhousing.

[007240z]

I put a new "KA" transmission in my 1972 240Z recently. Here's how it went: http://home.comcast.net/~zheimsothtn/transmission.htm

 

Steve.

[Young Z]

I believe the 5 speed KA transmission equivalent would be the 5 speed transmission that comes attached to the SR. The only difference between the two is the bell housing. What about using an RB trans?

[Whittie]

yeah ive done some looking but i cant find gearbox numbers from the s13 and s14 that you find here.

 

RB trans is an option but dont know yet, not enough research.

[Whittie]

Ok i want to put in a FS5W71C but i have a couple of questions:

 

of all of the differant ratios and engines they came on (sr20, ca18, ca20, rb20), is there any difference on being able to fit them to the L-series bellhousing? The price of the gearbox depending on the engine it was attached to alters by a MASSIVE amount so i want the cheapest i can get if they are all the same.

 

Are the gears all the same siz?. i.e. are they all the same width and as strong as each other.

 

Finally, is there any difference in the strength of the A/B/C boxes. i read about the different synchros on the C version but is that it?

[Xnke]

The C box from '87 and newer has 1mm wider gears, depending on the gearset. I don't know what gearsets are wide, and what are not, but my 200SX trans (CA20e) has all the wide gears except the countershaft gear, it has a thin spacer-gear along the actual gear.

 

The C trans will hold about 400whp reliably, according to a lot of the KA and SR forums, and the B trans will hold 250-300, usually. IF you use the B box countershaft bearing, the C trans is reduced to 250-300 as well, so you gotta machine the L bellhousing for the C countershaft bearing if you want the extra strength.

 

ALL the C box transmissions are similar in strength, from within a year. All of them will bolt up to the L series front case, with the same mods. No problems there, as far as I know.

[007240z]

Other than the thicker gears and the improved synchronizers, the other thing that is obviously different is the shifting mechanism. In addition to the ball and socket plate mounted shifter and the larger 1st-2nd shift rod, the shift forks are massive aluminum castings that engage the synchros a full 180 degrees and guide on the adjacent shift rods. The Rev-5th fork has been modified with an elaborate support/guide bracket assembly. All of this probably minimizes flex and binding in addition to increasing strength.

[z-ya]

I think you need to find a new transmission guy. There is no reason why a Z or ZX 5-speed cannot handle extended road racing with a 180WHP L6. Now if you were making a lot more power, I would look for something stronger.

 

We run a 1980 280ZX NA 5speed in our road racer. We have been running the same transmission for at least 3 seasons. No problems whatsoever. We change the oil twice a season usually.

 

The owner of the local transmission shop that rebuilt it for us worked on a Datsun race team in the 70's, so he knows these transmissions quite well.

 

Find yourself a new transmission guy and keep a spare in the truck.

 

Pete

[JSM]

Curious if your tranny guy raced his Z too? What problems did he have? Not bashing you but is it possible you are being to ruff on the tranny?

[Whittie]

Ok well, it's been a few days and while I’ve been looking on the net for some 'c' boxes the box has also come out of the car and been taken to the transmission guy. He pulled it out in front of my dad and it turns out 5th gear welded itself onto the shaft (??) welded some gears together anyways, causing the transmission to be effectivly locked in direct drive. The tranny guy (Z specialist btw) said that his diagnosis is that the mechanic who works on the car (not the tranny guy) has used a too thin oil in the transmission and it hasn't lubricated the gears sufficiently.

 

Therefore, good news is the box is repaired and now has all 'new' GOOD CONDITION components in it so it shouldn't be a problem. Did some research and it turns out that over the years transmission gear oil has become less and less viscous. My best guess is for increased efficiency, however, the older Z gearbox, built at the time of older oils, probably does not have sufficient lubricating properties to be able to effectively use the lighter oils. I have informed the mechanic and he is going to put thicker oil in from now on. I also have some SUPER slippery oil additive to put in there as well.

 

I'm still going to go ahead and get another 'c' gearbox as they are about 1/5 the price of an original Z tranny here and put on together anyways. If it's no good then I’ll use what I have, if it is good then I keep the switch.

 

JSM - Yes the Z guy did race his car. Drags mostly. But anyways, last year at an event they had a "masters" session where some really old coots came for a ride in your car with you during the practice session. Whilst on the lap they studied what you did and gave feedback after. The only thing he said to me (my dad as well too, interestingly enough) is that I was being too fierce with the up shifts and that I could be a bit smoother and gentler on the car. My thoughts at the time were "yeah, whatever, what does this guy know, it's only a frikin up shift!!". Well, been thinking back to that a bit after this incident and I gotta say, it might not have been correct, but it certainly couldn't hurt!! So, yes, probably was being too quick on the shifts and the clutch releases and need to pull it back a little. Not to granny speed, but to the point where it is smooth, the revs matched, and everything is not jolted when the power is applied again.

 

z-ya - That is what I was thinking as well. 180whp is not massive, it's a lot more than stock, but not to the point it should be breaking gearboxes. My only line of thought further on this problem is that perhaps the components in the box were old. Certainly when i blew third gear, on later inspection it turned out that the hardening on the gear had worn through and the gears were stress cracked, so it was only a matter of time. Hence, I am still thinking it might be better to start looking at some newer 'c' boxes. Low km varients from an s14 can be had here for 1/2 the cost of an old Z box. The older ones, also low k's for even less.

[woldson]

There is a really good thread somewhere about the oil and the lack of additives.

There are some opinions on what to use, but, no one disagrees out how good Royal purple is!

[z-ya]

I usually run 75w90 Mobil 1 or Valvoline full synthetic. I've also run conventional 75w90 when that is all I had laying around. I think you just had some components that were ready to fail.

 

Pete

[ezzzzzzz]

Can't go wrong with Redline either.

[260DET]

VL NA Commodores have the type of box you want but I'm not sure about the ratios. The shifter is quite different, it self centers in the 3/4 plane, bolts to the top with six bolts, its a big improvement. I know the RB20 box is good, there are others.

 

Does sound like you need a new gearbox man though.

[Whittie]

Cheers Richard,

 

I'ts on hold at the moment. Have "Round the Houses" next weekend and then i have a few weeks off uni so i'll have a good look in to it then

[Tony D]

I'm with Z-Ya on gearbox reliability.

Though in the same breath, for the exact same reason I've prepared some Sylvia KA/SR five speeds with the L-Engine front bellhousing section simply because finding the early model boxes (in low mileage good condition) is getting tougher even in SoCal.

 

But those KA powered Sylvias are everywhere, and the tranny came in other models, so the swap is possible with several other models as well.

 

So for me it was more of a function of being able to find late-model Sylvia boxes easier, so what the heck. Plus, you can get decent shifters for them to make the lever action very nice indeed.

 

I've been sacrificing L-Series Four Speed Bellhousings now for some time in support of the effort!

 

FYI, I've run over 40,000 miles (65,000 Km's) on my turbocharged L6 putting down between 275 and 350 to the rear wheels (which are 265's) and haven't had gearbox problems like you have.

 

I'd second the thought on getting a different gearbox guy, as well as experimenting with different lubricants to lengthen balk-ring lifetime...and make sure the oil you are using is compatible with the brass rings---the GL5 has sulphur compounds in the oil formulation that EATS the brass synchros in short order. With as quickly you are going through them, this may be part of it as well. The DID make steel synchros for some of these boxes, but the days of finding them is long past.

 

Good Luck, it's no fun when it keeps needing repair, and you're not really doing anything untoward with it.

 

I run redline lubes in the tranny now. Before I ran both NEO and Amsoil. For racing, synthetics are preferred.

[Whittie]

Well I’m in the middle of my mid semester uni break, and sure enough, plenty of work is happening.

 

I've sourced a gearbox from an s13 silvia, a bell housing, a bearing for the countershaft so I know how big to bore the hole, and a drive shaft from a 2+2 that I can molest.

 

The bellhousing and drive shaft are at the machine shop as we speak and should be finished by friday. The gearbox is coming out of the car next wednesday and then ANZAC weekend (25-27) the gearbox swap should happen.

 

Everything seems to be going well at the moment, it's been a lot of mucking around as no one can DEFINITLY say about MANY issues with these gearboxes so I’ve taken it in to my own to do a lot of the research.

 

When I have the box in the car I plan to do a big write up with LOTS of pics and to state and CLARIFY many of the questions about the 'c' boxes that it is so hard to find answers for, such as lengths, ratios and components. It's by no means a final stop for some issues as I don't have access to every type of 'c' box that Nissan made, but certainly it will answer many questions that I had trouble with whilst doing this install in an effort to hopefully help anyone else who is interested in doing it in the future.

 

Keep an eye out for my thread, although it will be a few weeks away yet. and NO, unlike many others I won’t be forgetting to do this write up. I promised the tranny guy (the z wrecker/expert) that I would keep him in touch with the swap and give him the write up once done so he can sell these gearboxes as a package instead of just upgrading synchro’s on the old zed boxes and having them fail constantly. I have been working with him on researching the install and he is donating parts and time to help me with it.