14 Bolt 9.5 Semi Float

[hotrodpc]

This 84 3/4 Ton truck I bought today came with what I think is the step child rear end for a 3/4. Its the 14 bolt GM Corporate 9.5 Semi Float Axles. Did the jack test to find the gear ratio, it is 4.10. Not sure if its limited slip, or locking diff. Obviously not a locker since I only jacked up one wheel and it spun easily while the other wheel stayed stationary on the ground. The guy I got the truck from said he would not swear to it, but says he is fairly certain is some form of posi since everytime he spun out in the dirt, it got sideways and both wheels were broke loose. RPO Code sticker in not in the glove box, and I do not want to pull the cover. Questions are since I have never dealt with one of these semi float 3/4 rears, How are they as far as strength, and in comparison to the 10/12 bolt half ton rear ends, and the 14 bolt 10.5 full float rear end like what is in my 86 3/4 ton. I know you can find 5 and 6 lug axles for this 9.5 rear if I decided to use it in a half ton. Also, if it were a locking diff or limited slip, does anyone know which one the factory would have installed? Would it also be the more common Eaton G80 Gov Lock that is not all that wonderful? I am just trying to find out all I can about this truck since I may recab it with the 1/2 ton cab that I have. Although so far, I am not real fond of this semi float rear, but that may be just because I don't know much about it. But I do like the 4.10 ratio and if I can find 5 lug axles and this thing is strong, I may put it in the half ton truck that I want to make a quick truck. So any info on this rear end would be great. Thanks

[scooter18155]

here is a cpl articles 75k30 posted in an earlier thread about axles when i searched about axles and axle swaps found them good reading the second one is all about the 2 different 14 bolt rear ends.

Rear Axle Semi-Floating and Full-Floating - Off-Road Magazine

GM 14 Bolt Axle Rebuid Parts - 4Wheel & Off-Road Magazine

[hotrodpc]

I pretty much know the differance in the 14 bolts. Just kinda wondering how strong the 9.5 Semi Float rear is. Is it a junk boat anchor prone to problems? Stronger than the 1/2 ton rears or where it falls in scale of junk to top of the line. Is it something I may want to keep or upgrade out of? I figured 75 would probably know, or anyone else who has had or used one. I am totally new to this rear. Never had one before. I was a bit disappointed to see this one under the truck, but it may be good. I like floating axles better. I hear this rear end is good for getting 6 lug axles and putting it in a half ton. I may very well do that myself to make the quick truck out of, but if I am going to do that, I am debating whether to just build up this 3/4 ton, or put this rear in the half ton. The half ton will be a bit lighter and lower to the ground. The 3/4 will be stronger drivetrain and brakes. I am just thinking of something without about 400 ponies, maybe 500, just depends on how rich I get when the time comes. I need to make some decisions on what I am doing with my trucks. Its ridiculous to have 5 of them now. So I want to get a plan together, and then start selling off the parts I am not going to use.

[75K30]

This axle is an upgrade form a 12 bolt, and is a pretty strong axle. The downfall is the fact that it is a semi floater. This means "c" clips.
in many cases this axle is a great upgrade. As far as strength does, it is strong, but carries a large package.
Truth be known, I would build a 9 inch ford alxle if a semi floater was to go under my 2wd. However I do not want to discredit the larger axle.

[hotrodpc]

You the man 75. Thanks. That is about what I was thinking. It just an upgrade over the 10 or 12 bolt rears. A glorified 1/2 ton rear end as far as I am concerned. So in your opinion, if you were making a peppy 2wd drive truck, would you use the 1/2 ton Chassis, or the 3/4 ton Chassis with a glorified 1/2 ton rear. I see advantages and disadvantes both ways as far as weight vs strength, and also ride height makes a difference too. I am thinking the 3/4 will be stronger, and stop better, but be a few tenths of a 2nd slower with weight and height being a factor. If I do this rear in the 1/2 ton I will have to get the 6 lug axles too and 6 lug rotors in the front and have more wheel options. I dunno, I think I know the differances, just have to decide which way I want to go with it, just asking which way you'd go with it.

[hotrodpc]

Curiosity got the best of me today, so I took the back cover off. Its a 4.10 peg legger with a kick stand. (Open Diff) I thought maybe I'd get lucky and get at least some good news out of it. I'd have much rather had the 10.5 full float rear, but the glorified 1/2 ton rear will be ok for what I intend to use it for I guess.

[semocoachworks]

I have a semi-floater corp 14 in my 86 suburban. i have 3.73's though. The only real trouble I ever had was the pinion nut backed off and crashed the ring and pinion. fairly easy rebuild though. new ring and pinion, bearings, shims and a little contact grease. I pull alot of heavy stuff with this and all-in-all, it does well for me.

[hotrodpc]

I don't know if someone has worked on this one, or if they just did an oil change, but someone has been it before. Its got bright orange silicone for the pan cover seal instead of a gasket and they were quite sloppy putting the stuff on too. Seems to be all nice and good in there. I see no burn marks at all, gear teeth to be fairly squared off instead of rounded off, so probably not a lot of wear. I think I'd prefer 3.73 gears. This truck originally had a Turbo 400 and 350 engine. With the 4.10, I will probably try to find a 700R4 trans for it when the time comes.

[semocoachworks]

Yeah, with that gear/tranny set-up, you might be pushing the rpm's up there a bit. make sure and check the bolt that holds the spider gear pin in. I've had these loosen up and destroy the housing and everything. good threadlocker usually solves that problem.

[hotrodpc]

With the tire size on there, it would be taching 2800rpm at 60mph. I guess that was OK back then with a 55mph speed limit. Geez hard to believe we drove that slow for so many years.