Front differential ring and pinion gear same size as rear?

[CASPER_97]

Cant seem to find an answer through older posts, i have a 1990 k5 blazer i recently re-geared to the rear end and am now looking to do the front, so here is the question, Is the ring and pinion gear the same size as the rear end. I dont want to tear apart the front end and have the incorrect size gears thanks for any help in advance

 

[bradshawtech]

Welcome, newby.
Replying to welcome you to the site, wish I could help you with your question but I’m not sure of a correct answer howe there’s plenty of guys on here that have lots of knowledge and experience that probably can.

 

[Wes Harden]

if you have 2 10 bolt axles then yes both should be 8.5" ring gear. Both need to have the same ratio, or match ie 3.73 to 1. 32 year old truck can have many changes to it from factory. Best to always double check.

Welcome to CK5 be sure to ask any question, or explanation of our answers. We might assume you know something, and it's ok if you don't.

 

[Blue85]

Yes, front and rear 10-bolt axles use the same ring/pinion, spider gears, shims and bearings. A front Dana 44 can easily be retrofitted in place and also has 10 bolts, but the internals are all different. Refer to this if you haven't: https://ck5.com/forums/resources/axle-identification-chart.10/

Be aware that 10-bolts went from 28-spline to 30-spline at the end of the 80's, so if you are looking at a locker, replacing the spiders, etc, you have to know which one you have. Like already said, don't worry about what is stock for your truck (unless you've owned it since new!), go see what it really has.

 

[Aegis43]

I have an '88 K5 with 10-bolts front and rear. I've owned it for 6 years and done some things to it but not gotten into the axle assemblies. It's had a life though. The rear housing has yellow wrecking yard paint pen identifying 3.42s, which works great with the 700R4 and 33x12.50s. Is the only way to determine whether it has 28-spline vs 30 axles pulling one out and counting the splines?

 

[Wes Harden]

Pretty much, think of it as an opportunity to change the oil and add a lube locker gasket.
Be very careful with the cross pin lock bolt, use a good 5/16" box end or socket. I prefer 6 point.

I use a snap on brake bleeder wrench

 

[CASPER_97]

Thank you gentleman so much for the input i really appreciate it, as for Aegis my blazer is a 90 and has 28 spline axles but having done research i assummed it had 30 spline axles and ordered a wrong carrier.Take it apart and count them.

 

[Aegis43]

Pretty much, think of it as an opportunity to change the oil and add a lube locker gasket.
Be very careful with the cross pin lock bolt, use a good 5/16" box end or socket. I prefer 6 point.

I use a snap on brake bleeder wrench

Thanks, Wes. And good advice on the lock bolt.

 

[Big Ray]

Thank you gentleman so much for the input i really appreciate it, as for Aegis my blazer is a 90 and has 28 spline axles but having done research i assummed it had 30 spline axles and ordered a wrong carrier.Take it apart and count them.

A 90 came with 30 spline shafts. Yours may have been changed at some time.

3.42 gears are equal to 2.93 in overdrive. That is hard on a 700r4. Low rpms equals low oil flow in the trans which equals more heat which shortens the life.

I changed my 89 from 3.42 to 4.10 gears. Much better. More power down low. I was very happy!

Of course you'll have to recalibrate the speedo. It can be a pain on the 90 as it has an electronic speedo.

Have to change some resistors to swap out. I have a how to in my files somewhere.

 

[Big Ray]

I'd get some 30 spline axles from a pick & pull. Cheaper & easier than sending the diffs back. Stronger than 28 splines too. Should be in 89 and up.

 

[Wes Harden]

You'll need the correct carrier bearing for 30 spline but will fit in same housing as 28 spline carrier

 

[Blue85]

Aren't the holes smaller on the 28-spline carrier? I thought I remembered somebody opening those up to fit 30-spline shafts. That should take the same bearing. Or you can get the 30-spline carrier/locker with a different bearing.

 

[Wes Harden]

Afaik the 30 spline is bigger od at the carrier bearing Id. The race cup is the same size for the housing.

 

[Aegis43]

A 90 came with 30 spline shafts. Yours may have been changed at some time.

3.42 gears are equal to 2.93 in overdrive. That is hard on a 700r4. Low rpms equals low oil flow in the trans which equals more heat which shortens the life.

I changed my 89 from 3.42 to 4.10 gears. Much better. More power down low. I was very happy!

Of course you'll have to recalibrate the speedo. It can be a pain on the 90 as it has an electronic speedo.

Have to change some resistors to swap out. I have a how to in my files somewhere.

1,750 rpm at 70 mph freeway cruise too low for a 700R4? I don't do much in-town driving where it spends much time in OD. It's not my daily driver. I'd never heard this about 700R4s.

 

[Wes Harden]

Yes. At 55 in 4th you'd be just off idle. Trying to accelerate with any light load will be difficult, ie up slight grade, towing.
At what rpm does your engine begin to pull?
I changed from 4.10 to 4.88 with 33s am at @2500 for 70

 

[Aegis43]

Yes. At 55 in 4th you'd be just off idle. Trying to accelerate with any light load will be difficult, ie up slight grade, towing.
At what rpm does your engine begin to pull?
I changed from 4.10 to 4.88 with 33s am at @2500 for 70

Actually, it seems to run really nice and acceleration feels very linear. It doesn't feel like it is particularly powerful, but what stock K5 in 1988 felt powerful? I do realize that with steeper gears it would feel like it had more power. I had the transmission rebuilt at a reputable shop in Phoenix in 2019, and it works very well. It does kick down to 3rd pretty quickly once it encounters a grade.

Based on your earlier post I reached out to my contact at the transmission shop and asked him about low rpm and heat in 700R4s being an issue. He replied, "No. Heat is caused by lack of coolant flow, or something coming apart causing restrictions." I'm not discounting what you said. Just sharing.

 

[Big Ray]

Sounds like you got a well built unit.
My 3rd failed 700 is in my driveway waiting for a NV4500 swap.
To be fair, all of mine but one were stock and in used vehicles.

The one was in a truck Dad left me that he bought new. Bone stock. 3.42 gears. Stock tbi.
Had the tranny rebuilt and swapped to 4.10 gears.
Mo' better!!

 

[Wes Harden]

My 4th with 4.88 my is 3.41