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This started as tranny advice but due to the current tranny trend let's keep this on transmissions. I have a 720 that I have owned for 28 years. It is raised and rides on 31s. I went through 4 fs71b trannys before swapping to a 1988 fs71c trans. 12 years all good no issues. Swapped in a single cam ka24e and in less than a month the trans has blown it's gizzard. I don't want to rebuild. Is there a newer better trans to seek out? I see the v6 trans conversion kits but it will be kind of spendy and with issues associated with a conversion. I just want a reliable dd and as far as I can tell the pre 1990 trans are shit.

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Considering as how the 71c is stock behind a kae, i would say the additional power merely exacerbated an existing problem. I'm not overly familiar with d21s destroying transmissions just because of 31s and a lift.

 

All that being said, with all that Swapping going on, have you checked your trans output angle vs your pinion angle?

 

How hard do you flog this thing? I've never even blown up a 71b in my ten years of 720 4x4 ownership. I've put a fair number of miles on my truck with 31s and a 3 inch lift, but i rarely brawl up anything more aggressive than a dirt road.

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Sorry about the double post. Anyways the first 3 71bs had the classic bad countershaft bearings and the fourth fifth gear just walked off the shaft. So that's when I went to the c version and all has been golden the last 12 years. The ka24e swap is a little more work than implied but it all worked out and has been a joy to drive the truck again. I am not flogging it and don't Rev above 4k. My question is did the the c version change after 1988 or is it the same that nissan put behind the ka24e. I don't want to go through the process of changing trans on a regular basis again.

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Four 71Bs in 16 years! or one every 4 years? A 71C lasted 12 years and only one month with the KA tells me your simply abusing them. 31's and raised makes this a 4x4? Was the oil replaced at 30K or 5 year intervals and kept topped up?  

 

 

 

The 71C was used and the KA makes a bit more torque. The 71C will hold up under NA VG30 engines in the Hardbody and zx. The later FSR30A  in the '87 and on S12 and zx turbo would be bullet proof but never came in KA trim.

 

Just get another 71C you have already done the conversion for it.

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Just exactly what part of the trans gave up the ghost? I bet it was a bearing, in which case, was a problem not related to the new engine's power. Those transmissions can handle 250hp + so you can rest assured that it won't happen again.

 

Rebuild vs buy another trans? Well if you rebuild (or have someone do it for you) what you already have, you know there won't be any surprises. As with anything though, find a person that does transmissions, because there are little tricks that help with the process and things specific to this type of trans to watch out for.

 

What will it cost to rebuild? If you bring it to someone who knows Datsun transmissions, it will likely be cheaper than if you brought it to, let's say, AAMCO. But I would expect to pay about $600-$800 to have it completely gone through.

 

or... maybe just have it repaired. Probably only cost you a buck fifty to have it repaired (assuming it's a bearing).

 

As I said, there are tricks. Make sure the new coutntershaft bearing has a seal on both sides, because all the garbage that gets thrown around inside a Datsun trans passes through the middle countershaft bearing and the seals help keep out the junk. The 5th gear thing is common too, but if you know what you're doing, it can be made to never happen again. I made a long socket for tailshaft nuts that I can use on my impact gun. Basically, I cut a socket in two and then welded a long piece of tubing in the middle. You have to use red loctite on the threads and then stake the nut. But they come loose because of wear in the thrust washers. Flip the washer over, re-grind it flat, or get a new one.

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Thanks for the replies now let me admit I am a complete MORON for posting before trans CSI. I heard a loud pop while driving and although the engine was running fine power obviously wasn't making it the the rear wheels. It acted like the transfer case was in nuetral. I was on the side of the road engine running in gear and I could look under the truck and no movement at the trans output. Push in the clutch felt fine and there was no unusual noise. Ran through all gears same results. Gave up and called AAA. after dropping the trans metal fell out of the clutch. The disc is sheared off. It is an exedy with a new flywheel. Ran fine for a month and there were no noises or any indication of a failure. I jumped to conclusions and sorry for wasting people's time. I am off for a new clutch and hopefully have it back on the road tomorrow.

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