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Old 12-26-2010, 12:01 PM
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Saginaw refuses to shift when hot

I have a Saginaw 4 speed behind a 350 in my 3rd gen Nova. It was an auto car so its been converted with new clutch linkage from J&W. When the clutch is properly adjusted the car shifts fine for the first 5-10 minutes then first gear and reverse begin to clash/grind when attempting to shift into them. Gradually, 2nd gear will begin to clash then 3rd and so on as the tranny warms up. I've had the clutch and tranny out 3 times and nothing appears amiss. The pilot bushing is fine (I even replaced it once just to make sure). The freeplay remains proper. I even tried redrilling some holes in the Z-bar to give the throwout bearing more travel (at the expense of increased pedal effort) just in case the repop z-bar wasn't made quite right. I just tore the tranny apart expecting some trashed roller bearings or something...anything, but the internals look good. I'm at a total loss as to what would cause my tranny to shift worse and worse the longer it gets driven. Help!

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Old 12-26-2010, 02:53 PM
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Hi,
It sounds like the center bearing is heading south. When you change it do the front one as well, they are usually the first to go. The thrust washers in them aren't solid washers but a wave type, and they allow excessive end play when these wave washers get worn allowing the cluster gear to travel back & forth in the case. To fix this, use solid flat thrust washers in place of the wave type and set the end clearance at .000-.005 in. Also, the front end of the cluster gear has a stamped steel plate with the same cut as the front gear loaded with springs against the gear cut, this is to stop backlash between the input shaft and cluster gear. This plate actually is loaded against the input shaft the opposite direction the cluster gear teeth are, so..there is no backlash. If the springs get broken, and/or the plate fails, backlash will be present, and the cluster to input interface will make noise.
It also makes a difference in the trans oil you use, use 80W90 or 85W90 gear oil, no lighter weight.
Good luck,
Rich
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Old 12-26-2010, 03:20 PM
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Thank you very much. You've given me some new things to look at inside the tranny. I have a rebuild kit handy and will give your suggestions a shot. I totally forgot about the antilash plate and springs.
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Old 12-26-2010, 03:51 PM
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What? No banna peelings?
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Old 12-26-2010, 04:58 PM
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If you are raking when you try to put it in reverse you have a clutch problem ,it's not completely releasing .
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Old 12-26-2010, 06:03 PM
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Sounds like you might have the wrong throw-out bearing to short/not long enough. JMO
And as stated the quality of oil could make a difference also.


Cole
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Old 12-26-2010, 06:52 PM
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I thought clutch problem at first too, but the tranny shifts absolutely perfectly for the first 5-10 minutes or so. It progressively shifts worse and worse the longer I drive it. The gears with the most mechanical advantage (1st 2nd and reverse) are affected at first, gradually worsening and spreading to 3rd gear as well.
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Old 12-26-2010, 07:43 PM
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Quote:
Originally Posted by eloc431962
Sounds like you might have the wrong throw-out bearing to short/not long enough. JMO
And as stated the quality of oil could make a difference also.


Cole
Perhaps after the clutch and tranny get hot, jack it up and get a friend to put the peddle to the floor and do a feeler gauge check between the disc and the flywheel. Make sure the pressure plate is releasing all the way.

Oops, got the tranny out all ready. Sorry.
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Old 12-26-2010, 08:17 PM
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It's easier to jack up the car and support on jack stands. Have helper wife get in the car and put the car in first gear. You then crawl under car (unless you can get the wife too) and try to turn the drive shaft by hand. Then have the the helper wife push in the clutch and again try to turn the drive shaft. It should turn with almost no effort. Now you can get out from under the car and start the car and run the engine in gear until the engine adn trans gets to operating temperature and turn off the car. You get to crawl under the car( unless your wife will) and have whoever put the car in gear and again try to turn the drives haft with the car in gear and with the clutch in or out. If the clutch works Ok then you have a transmission problem.

This way is quick, easy, adn won't leave you on the side of the road.
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Old 01-04-2011, 08:06 PM
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Saginaw 4-speed problem

You most likely have the wrong clutch and pressure plate. I installed a Saginaw 4-speed in my El Camino and had the same problem. The clutch I purchased was for a Camaro and the shop told me it was the same. However, it must have been for use with a hydraulic throw-out bearing, and since mine has manual linkage it caused the prongs/springs on the pressure plate to over heat and bend not allowing the clutch to release. I replaced the clutch, pressure plate and throw-out bearing with a Center Force dual friction from Summit Racing and the problem went away.

Good luck
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