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Seven Two Oh No

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About Seven Two Oh No

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  • Location
    Northern CA
  • Cars
    1985 720 4x4

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  1. The speedo in my 85 would occasionally exhibit similar symptoms - would read correctly at lower speeds but fluctuate 10-15 mph higher at cruising speed. Changed the cable and the issue stopped. To Mike's point, I'm not sure why this was happening as the cable simply rotates based on trans output, but new cables are under $10 on Rockauto so worth ruling that out before hunting for a new gauge.
  2. Not sure where you're at in CA, but there's an 85 at the Pick n Pull in Oakland that I checked out today (2/7). It was missing the carb but everything else seemed to be there. Doubt it will stay this way for long with the weekend coming up.
  3. Seven Two Oh No

    Driver seat

    Here's a link to another thread on this very topic - https://ratsun.net/topic/42162-compatable-seat-swap/
  4. Update - did not find any damage to the unit beyond the pilot bearing, although apparently Midwest Transmission did not install a countershaft bearing front shim or replace the (broken) oil gutter. Checked gear end play and O.D. gear was binding on thrust washer (thanks to Stoffregen Motorsports for pointing out this scenario in a different thread) - I loosened the main shaft nut and retightened until end play was in spec and now everything seems to be working properly. Still have not identified the cause of the initial lock up, but it's worth noting that I never checked end play after rebuilding the previous transmission (first time - lesson learned), so it's possible both units had too tight of clearance between the O.D. gear and thrust washer. That, combined with driving for a few hours may have closed the gap and bound the O.D. gear to the output shaft. Since I was driving in O.D. I didn't notice, but when I downshifted into third I was basically in two gears at once and the trans locked up, probably jamming the mainshaft into the input shaft. The shifter was in gear but there was no power to the wheels because the trans was locked and the clutch was slipping as a result. After I shifted into neutral, the input shaft was likely binding on the main shaft until the pilot bearing gave way and was slightly milled in the process (I heard a high-pitched whine "spinning out" when the trans loosened up). The O.D. gear and thrust washer were still tight together even after cooling down (possibly due to shaft locking up and distorting some things), which led to hard shifting and binding in all gears except O.D. This is very much a working theory, so I would appreciate any thoughts you guys might have. Going to order a few parts and put it back together, although I likely will never completely trust it again.
  5. There are a series of videos on Youtube showing the complete disassembly and reassembly of a 71B that helped during my first rebuild. First video is here, and you can find the rest on that page - <https://www.youtube.com/watch?v=eTdf7ncLy0A>
  6. As an alternative to buying new felts, I fixed the window rattle in my 85 by gluing in a length of 1/2-inch OD vinyl tubing into the channel, then tracing and and cutting out a 1/8 to 3/16-inch strip down the middle to act as a guide for the glass. Been working great for me for the past few months I've had it in, and beats paying for those felts.
  7. I appreciate the input, everyone, and agree that it is suspicious that I've had the same failure on two different transmissions. I do not drive or shift aggressively, however, and have always kept the trans topped off with Redline or Synchromesh. I've also considered the possibility that the transfer case is somehow involved, but the unit works fines in all ranges without noise/etc. I'll take a closer look at the motor/transfer case mounts though, and will pull the other gear clusters/shift forks to inspect (particularly 3/4).
  8. I have a stock '85 720 4x4 with a FS5W71B and have had three transmission failures over the past two years. This 71B has the larger 62 mm countershaft bearing and none of the issues are due to that bearing failing. The general symptom is that the transmission will briefly lock up (with a clunk) directly after a shift, and then there will be no power to the wheels, despite the shifter being in gear. I can then pull the shifter back to neutral (with some effort), put it back into gear (still no power to wheels) and rev the engine a little until whatever is binding loosens up and the transmission grabs. This happened a few times with the original transmission (generally on surface streets at low speeds), so I took it apart, did not find any obvious issues, and rebuilt it with new bearings (except the needle bearings) and synchros. Problem solved for about 12 months (I only drive ~5-7k miles a year) but then I was on a four hour drive, cruising in 5th most of the time or in 4th for uphills. I got off the interstate, downshifted and slowed, then dropped it in second at which time the rear end bucked when the transmission locked up. Pulled it apart once I got home and found the thrust washer behind 5th gear had snapped in half and that the input and tailshaft were bound together, so that turning the input spun the output in neutral. I had not changed the mainshaft needle bearings, so I suspected that may have been the cause. I then ordered a rebuilt unit from Midwest Trans, which worked great for 16 months (6,500 miles). Then, same failure - four hour drive (few uphills this time), mostly in 5th, came off the interstate, downshifted to 4th then into 3rd when it locked up. It still drove but was difficult to engage gears. Despite the low miles on the unit and only being 4 months past warranty, Midwest refused to cover any repairs (they would inspect for free but I would have to cover shipping, etc.). So I took it apart to inspect. Input and output shafts are binding in neutral (can turn separately with some effort). I pulled the main drive gear and found the needle bearing had been milled at the mainshaft face (see linked pic -having difficulty embedding), and there is pitting on the mainshaft where the bearing face sits. All gears with the exception of 5th are difficult to hand-turn when engaged, and reverse is almost impossible to hand-turn. I'm assuming the transmission locked up and compressed/distorted all of the needle bearings on the mainshaft but wanted to get the opinion of the forum. Particularly, how could the transmission be in gear with no power to the wheels? The clutch allowed me to shift into gear but everything locked up when I released the pedal. There is no damage to the input splines or the clutch so I don't think the problem is on that end, but the in-gear-no-power is very perplexing otherwise. Could be that the clutch is just slipping when the transmission is locked up, however. I would appreciate your advice. https://www.dropbox.com/s/ax489j2ey98lvm2/01_Main Drive Gear Needle Bearing.jpeg?dl=0 https://www.dropbox.com/s/9vz9k5ub29nc0x3/02_Main Shaft Bearing Surface.JPG?dl=0
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