can you swap a 4x2 rearend with a 4x4 rearend or do i need to get a different drive shaft

 

The 2wd rear end is narrower.

 

When did GM change the S10 Blazer from a 26 spline axle to a 29 spline axle?

I have seen26 spline axles advertised for 1983-1998 S10 Blazers andI think 1991 S10 Blazer was the first year for the 29 spline axles.Is there a wayone can tell if the vehicle is equipped with a 26 or 29 spline axle without removing one?

 

You mean 28-spline right?

Looks like it was sometime between 1988 and 1990 that GM switched from the 26-spline to the 28-spline 7.5"/7.625" rear end in the S-series vehicles (S10, S15, S10 Blazer, Sonoma, Astrovan, etc). You would be more likely to find the 28-spline axles in the 1988+ 4wd trucks and the 26-spline axles in the 88-90 2wd trucks. This was probably as they phased out the usage of the 26-spline axles.

Some differential manufacturers peg the 1988 model year as the first year of the 28-spline usage, but I have found enough references to 26-spline axles being used up until 1990 to mention it as being a possibility. If you were looking for one, I would try to find one out of a 91 or newer truck. If you did not mind swapping the master cylinder, you could go with one from a 98+ which would have rear disc brakes.

 

Your information is correct. Continued research hasconfirmedthat my 1991 S10 Blazer 4WD has28 spline X 29" long axles with a7.625" ring gear.It appears the 28-splineaxleswere used on all1988 to at least 1997 S10 (T10) Blazers with 4WD. Some 1989 - 1993 S10 (T10) 2WD Blazersused 26-spline axles with a7.500" ring gear.The axle housing is 54" between the brake backing plates.

I am not interested in changing complete axle housings to obtain rear disc brakes at this time, unless I determine that my rear drum brakes are not working. There is no adjustment slots in the backing plates so I gotta take off the tires and drums to in oder toadjust the rear brakes. Now I understand why GMdecided to introduce rear disc brakes. I needed to know the axle spline countbecause I am thinking about replacingthe Gov-Loc (G80)3.73:1 (GT4) differentialin my 1991 S10 (T10) Blazer SUV 4x4 with anAuburnPro Series or Zextel Torsendifferential. I just installed my Summit aluminum differential cover/girdle and that got me thinking about theweak Gov-Loc part time locking differential.Auburn and Torsenoffer locking differentialsthatfitmy GM 10-boltbut with 28-spline axles only.

I understandthe Torsen differentialis the one that is more durable, bullet proof and can withstand an impact load that would destroy a Gov-Loc.

 

You will not get the impact load with a torsion or true limited slip diff. It has been awhile since I have looked at the design of the Auburn diffs, but if it is a cone type limited slip, then I'd pass. As the cones wear, they revert the diff to open operation with no hope of rebuilding like the clutch type limited slip diffs.

What are you planning on doing to your truck to need a reinforced girdle, let alone a torsen differential?

 

I wanted to change the OEM gear lube in the rear end and I decided to put a new cover on it while I was at it.I chosethe Summit cast aluminumgirdle/cover for the added strength.Now I feel like the Gov-Loc is the weak component then nextwill be the axles.The10-bolt limited-slip differential and especially the Gov-Loc differential isnotoriouslyweak. I admit, a 4.3L V6 enginewitha 4L60 automatic transmission will not puthigh impact loads on the weak rear end.I have always been one who uses "overkill" when building anything but only if the extra cost isnot prohibitive. For example, when I prepare myspareV6 heads, I willtap the heads and installARP 7/16" BB Chevyscrew-in rocker studs, use appropriate Comp Cams roller rockerswith amild aftermarket or OEM roller cam and fresh valve springs! It takes no more effort and very little extra cost to installmore reliablecomponents that it does to install theweakstuff.

GM has beeninstallingparts in theirvehiclesfor 38 years just to reduceproduction cost and comply with the EPA mandates. They are not concerned in the least about reliability. Thatwas caused by the UAW and their constant demand for higher wages and benefits . Theonly way the big three could recover the labor cost is to reduce the reliability and quality of their products. Because of that, the big threewill be bankrupt in five to ten years and all Americans(but not me) we will be driving foreign madevehicles. I will still be driving a vehicle that was built to last.

I may be wrong but I don't thinkGMwas dumb enough to installGov-Loc differentials in S10/T10 Trucks with a manual transmission. That is because of the impact load on the differential if someone dumps the clutch with one or bothrear tires ondry pavement, even with what little torque a wimp of an engine like a 4.3L V6 has. That tells me that even GMadmitted the Gov-Loc is aweak differential. Even the the Syclone and Typhoon did not put a high impact load on the differential. A turbocharger cannotspool up fast enough .

I may even decide to install388 CISB Chevy stroker enginein "The Blazer" 4x4 before I die. I have already started looking at parts and cataloging themfor thatproject. When you reach my age, you learn totakeshort cuts andmake plansaccording to whatlittle time you have left.

 

The only real time that you get high impact loads that would compromise the Gov-Loc diff is when you get one wheel spinning and then the governor dog slams in locking the two wheels. If you have good traction, then the G80 lasts quite well. They can actually perform very well if you know how to get them to lock up before you really put the power to them.

 

The Gov-Loc is a very good differentialbut only within the limits forwhich is was designed.