Strength of Ranger 7.5 vs Ranger 8.8

[tinman_72]

Years ago I found a 3L73 8.8 from a Ranger at a you-pull-it place, so I grabbed it for my four cylinder Ranger that had 3.45 7.5, mostly for the limited slip. Whenever the topic of fitting a V8 comes up with my friend he says, "Yeah you already have an 8.8!". I always reply that I would want to do the Explorer swap because I remember seeing on this site before where someone made the claim that the Ranger 8.8 is really no stronger than the 7.5. I have searched and cannot find it again. Is it just because the axles are both 28 spline or is there something inferior in the carrier?

 

[Captain Ledd]

The carrier-ish, the 7.5's tend to chew up spider gears at higher power levels. I say "-ish", because I swear there was someone around there that did desert racing with his, and he welded up his 7.5 for giggles and to see when it breaks. After two years it hadn't broken, and he ended up swapping in the 9" that he had already built for it "when it breaks" for sake of spending all that money on the axle and not using it.

Both use the same shafts, and they are of pretty good quality steel and heat treatment, superior to those of comparable Dana axles.

 

[don4331]

Ranger 8.8 is really no stronger than the 7.5.

Tinman_72:

The following are the differences between 7.5 and 8.8s with split of various 8.8s.

7.5 has hypoid offset of 1" while 8.8 offset is 1.5" Note: What makes 9" so strong is its offset of 2.25".
Larger hypoid distance allows more gear teeth to be in contact simultaneously. More teeth in contact = stronger but less efficient; pick your poison. The lower the ratio (higher numerically), the bigger the issue. You probably aren't putting 5.13s in so difference isn't that significant.

I have the pinion bearings as identical with exception of the "super" 8.8 found in F-150s

8.8 carrier itself is slightly over 1" larger, but then again carriers are rarely failure point. Ranger 7.5" carrier has 3/4" spider gear shaft; Explorer have 1". This is probably why 7.5's are more apt to chew up spider gears at high power levels.

Carrier bearings for 7.5" are 2.891, while 8.8" are 3-1/16". (Not 100% sure about Super 8.8)

Rangers use exact same 28 spline axles in both 7.5 & 8.8. Wheel bearing are 1.405". Explorers are 31 spines with 1.62" wheel bearings. F-150s (Super 8.8) are 31 spline with 1.705 wheel bearings. There are differences in tubing diameter/thickness.

So, if you want more load carrying "strength", the Ranger axles are rated for 2,700lbs, the Explorer @ 3,200lbs and F-150 @ 3,800lbs.

Given the most common failure is the axle; strength of Ranger 7.5 vs 8.8 is basically same.

In a low ratio/big tire 4x4, some differences are there (but you still probably break the axle 1st). Differences are probably there when doing MTBF testing at higher power levels too.

 

[alwaysFlOoReD]

Given the most common failure is the axle

What exactly do you mean by axle? The housing, tube, or shaft.

 

[Curious Hound]

One exception is the 8. 8" 31 spline axles that were in the Ranger FX4 models for a few years. Most of this information is in an article in the tech section on this site.

This message composed solely of recycled electrons. Go green!

 

[don4331]

What exactly do you mean by axle? The housing, tube, or shaft.

The ones I have restored, ones I have have come across in PnP; it is the axle shaft which is damaged other than those with specific accident damage to the housing).

I admit my sample size is only few dozen, and Alberta/Saskatchewan locations.

 

[Mac]

From above by Don, "So, if you want more load carrying "strength", the Ranger axles are rated for 2,700lbs, the Explorer @ 3,200lbs and F-150 @ 3,800lbs. " Those are for the complete axle assembly, due a lot to bigger bearings. Actual axle shaft max are close to 4600 ft/lbs for the 28 spline and 5100 ft/lbs for the 31 spline. Ratings from several axle manufacturers
Dave