720driver97 Posted December 6, 2015 Report Share Posted December 6, 2015 In my 4x4 truck I have the zl71b#3 but I can't get it in reverse, when I got the truck the guy I got it from have another transmission the zl71b#1, can I put the other transmission in? What's the difference between the two? The guy said the #1 was for a 2wd but they look the same to me 1 Quote Link to comment
datzenmike Posted December 6, 2015 Report Share Posted December 6, 2015 The '83 transmission has a reverse check sleeve mounted on the driver's side of the tail just behind the adapter plate. It's job is to prevent a shift directly from 5th down and hitting reverse. To enter reverse you must shift into the neutral gate and bring the shifter over to the left slightly, then slide right into the 5th/reverse gate and pull down into reverse. You probably know this. The check sleeve may have fouled up and blocked any shift into reverse. I would remove the reverse check sleeve and see if this fixes your problem. Only two 10 mm bolts. Any other reverse check sleeve will fit and replace a bad one. They are found on all L, Z, SD, CA series 71B transmissions after '80. The #1 and #3 on the main castings are (in my experience) just a quick way of marking a mold. You'll notice that it looks scratched on with a nail? It (probably) denoted a small revision made to the mold. Possibly the two molds were used in widely different foundries. (the one above is the tail casting and was molded in Australia NMCA) As long as the two transmissions are the same length they will fit. A 2wd will have a speedometer pinion sleeve in the tail, the 4x4 won't as the speedometer cable is driven from the transfer case. A 4wd transmission will always have a wide ratio gear set inside that makes low speed crawling easier for a heavier 4 wd truck A 2wd generally has a mid ratio gear set although some options like the Cab/Chassis and Diesel use a wide also. A 2wd transmission will work fine in a 4x4 but if you are into serious off road you may notice a reduction in your crawl capability specially with large tires. If you want to confirm the internal ratios (outwardly you cannot tell what gears are inside by just looking but..) you can ask the transmission to show you.... Get someone to help you. Mark the input shaft where the clutch splines are (say at 12 o'clock) and then mark the output spline on the tail. (also at 12 o'clock) Shift into 1st gear, turn the input exactly 20 times. Have your helper count the output turns. If they get 5.5 turns you have a wide ratio suitable for a 4x4. If you get 6 turns you have a mid ratio transmission. There were no close ratio transmissions that would fit a 720 Z24 engine but for those that care 6.5 turns would be a close ratio . 2 Quote Link to comment
720driver97 Posted December 6, 2015 Author Report Share Posted December 6, 2015 I pulled the transmission last night and can hear metal in there so I'm assuming something striped out or broke, I haven't had reverse since I bought the truck last year I didn't know how to shift like that I assumed u just pull it back into gear. If the gear is striped can I take the one from the other transmission ? 1 Quote Link to comment
datzenmike Posted December 6, 2015 Report Share Posted December 6, 2015 By removing the tail you can access just about everything reverse related. There is a reverse counter gear engaging a reverse idler which reverses the spin. Then a reverse gear beside 5th moved by the shift fork engaging the reverse idler when shifted into reverse. You are looking up from underneath a 5 speed transmission with the front to the bottom of the page. The gear with the teeth stripped off of it on the right is the reverse counter gear. It is driven any time the clutch is engaged. The gear on the left is the reverse idler gear. It is permanently engaged to the reverse counter gear and is driven by it at all times the clutch is engaged. The gear with the brass synchro ring above it, behind and above the reverse idler is the reverse gear. It slides forward (or down in the picture) and engages the reverse idler, when the shifter is placed in reverse and now power can be transferred to the mainshaft when the clutch is released. The synchro is for the 5th gear above it. The reverse idler is simply held in place with a snap ring. The reverse counter gear is splined to the counter shaft but also has the 5th counter drive gear above it, (also splined to the counter shaft) and a large nut staked on the end.to hold them on. A large wrench and a gear puller will get them off. I doubt it's the larger reverse gear. That would take a lot more work to remove and replace. 2 Quote Link to comment
720driver97 Posted December 6, 2015 Author Report Share Posted December 6, 2015 Ok thanks 1 Quote Link to comment
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