Finally underway with conversion from TH350 to Saginaw 4 speed (3.11 first). Car is a '67 Convertible with a rebuilt '68 Bonneville 400 transplanted 5,000 miles ago. Doing this on the ground, wheel cribs, with my 25 yo son as father/son project. Pulled the TH 350 and driveshaft with yoke. Yoke is 4.25 inches, 27 spline, slides all the way into TH350, 1" exposed when attached at differential and slides easily. New steel flywheel, disc, clutch, pilot bearing, throwout bearing, date correct BOP bell housing ... all went on easily. Tranny on floor jack finally slid in after removing distributor cap and tipping engine back a bit. Bolted on 2-groove 27 spline Saginaw 4-speed, shifter hole a bit off, but everything fit perfectly including cross member support. Problem : Yoke won't slide onto output shaft of Saginaw. Goes on about 1.5" then binds. 3" of Yoke shaft exposed, and driveshaft about 3" too long. Saginaw was rebuilt by 76 yo GM transmission tech from the 60-80's time. He does nothing now but rebuilds Muncies,BW, Saginaw, all linkages, and all period correct Hurst shifters. The tranny came completely set up and linkage adjusted. All that argues against having twisted output splines if he is knowledgeable. New seals. Many new internal components. The yokes must not be compatible ? Am I hitting the tailshaft bushing ? Where do I go from here and what Yoke do I ask for ? Tell me I don't have to pull tranny ..... Thanks !
Make sure there isn't any rust buildup, try to go over the splines in the yoke with a wire brush and clean it out with brake clean and blow it out. Could also be the tail shaft bushing is just to tight on the yoke. Also look at the splines on the output shaft on the transmission and check that isn't all rusted up. Also sounds like your drive shaft is to long.
Thank you - will do as recommended. Appreciate your advice - I'm frustrated.
Drive shaft too long .... why ? Not enough yoke showing (~1") when in previous TH350 ? What amount of exposed yoke should I be looking for from shoulder of yoke to tail shaft ?
with the car sitting on the suspension you should have 3/4 inch of travel inward with the yoke in the tail shaft. This is with the u joint seated in the rear yoke.
Got it - that's what I ended up with once it went in. I think my measurement description when eyeballing the 2 ends when not fully engaged were not accurate. Switch from TH 350 to Saginaw 4 speed was identical - same driveshaft length, same yoke.
So this is what happened. I cleaned up everything as Chief recommended. Called transmission rebuilder in Vermont (great guy by the way and super resource - "Old School 4 Speeds"). He said output shaft was true, not twisted. Bushing was pressed on with shop press and is tight when new. Said "they can take some force" to get it in the first time. Cleaned the outer yoke with fine emery cloth, oiled the outer and inner yoke surfaces, and it tapped right in with light rubber mallet from differential end. Relief ....
