re-gear or axle swap plus re-gear?

[Evil Bob]

1988 K5 Crate 350 with approximately 40k 4" lift 35" tires... The Transmission slips here and there or more of a searching for OD in and out kinda thing. I have no idea of the stock gears but I have a sneaky feeling this is the cause. Please help me figure out the best ratio to go with. I love driving her as a daily and sometimes take 2.5 hour trips on the highway with her. I also do very lite 4x4ing on the beach mostly. I am leaning towards Yukon 4:10/4:11 any input would help out thanks...

Adam

 

[bucket]

4.56 would be ideal, but 4.10 would work too. Your current ratio could be 3.08, 3.42, or 3.73.

If hills or strong headwinds are something you are up against at any time, the 700r4 still won't be 100% happy with 4.10's.

 

[Evil Bob]

4.56 would be ideal, but 4.10 would work too. Your current ratio could be 3.08, 3.42, or 3.73.

If hills or strong headwinds are something you are up against at any time, the 700r4 still won't be 100% happy with 4.10's.

I was hoping 4:10’s would get it done... I really enjoy taking her on the highway... I always assumed 4:56’s 4:88’s were way to much for highway driving. I want something that will not tax the transmission too much and work nicely down the road.

Long Island is flat so hills and headwinds are not much of an issue. I just don’t want to spend the money twice for making a bad choice.

Thanks,
Adam

 

[4WDKC]

410s with 35s is like 1800 at 70, this is very similar to 342s and stock tires. It is not performance minded and with a stock 350 tbi it had to downshift for hills/wind passing cars with less than mile of room... That siad switch axles means new wheels also and that can gear expensive... swap your gears to 456s would be cheaper if you wont buy used wheels.

 

[Evil Bob]

410s with 35s is like 1800 at 70, this is very similar to 342s and stock tires. It is not performance minded and with a stock 350 tbi it had to downshift for hills/wind passing cars with less than mile of room... That siad switch axles means new wheels also and that can gear expensive... swap your gears to 456s would be cheaper if you wont buy used wheels.

Gotcha... thanks

I do want to save some $$$ so axle swaps just seems overkill for me. I love to tinker but in my 43 years I have learned tinkering gets very costly and 90% of the time it’s not needed rather wanted (more power grrr)... drivability with reliability plus a hint of fun factor is all I really want. Besides just going down the road in my K5 is fun. Everywhere I go specially in the summer I get thumbs up and smiles, my two boys love it as well.

 

[RoryH19]

I've been looking at gear change axle swap for 82 K5. At this point the engine, trans and t-case have been changed, what's one more thing.
I can find 14 bolt, 6 lug axles from 88-98 4x4 chevy trucks for around 200 in my area. They are 3.73's with the GM locker which works for my 33" tires.
Much better than the 3.08's it has from the factory.

 

[4WDKC]

I've been looking at gear change axle swap for 82 K5. At this point the engine, trans and t-case have been changed, what's one more thing.
I can find 14 bolt, 6 lug axles from 88-98 4x4 chevy trucks for around 200 in my area. They are 3.73's with the GM locker which works for my 33" tires.
Much better than the 3.08's it has from the factory.

It is better than your 308s but will still be lacking, 410 is supposedly ideal for 33s.

 

[RoryH19]

It is better than your 308s but will still be lacking, 410 is supposedly ideal for 33s.

Hard to find the 4.10's in the 6 lug from factory.
I think with my 6.0 and 4L65e I'll be ok.

 

[Camar068]

I've got a local guy that's going to do front/rear including carrier bearings for $525.

 

[77 K20]

32's on my old GMC Jimmy were even enough to bog the engine down and it was bad for it to shift in and out of overdrive all the time. I leaned just to drive around in drive all the time unless I was on the highway doing 65.

At speeds of 45-55 the constant hunting was so annoying.

Can at least do this in the meantime before you regear.

 

[Evil Bob]

32's on my old GMC Jimmy were even enough to bog the engine down and it was bad for it to shift in and out of overdrive all the time. I leaned just to drive around in drive all the time unless I was on the highway doing 65.

At speeds of 45-55 the constant hunting was so annoying.

Can at least do this in the meantime before you regear.

That's exactly what I do now... I keep it in D and when on the highway OD.

 

[Evil Bob]

Thanks for the help... I ordered 4:56's from Yukon with the install kit and seals for around $800. A well known local 4x4 shop is doing the install $750 labor. Fingers crossed...

 

[rpcraft]

To be honest 31's are enough to make it bog down at cruising speed to some degree. The 3.08's were garbage for anything with anything more than a 29 inch tire and a 1.1 final drive ratio like the TH350 and TH400 had. It became even worse when they swapped to the 700R4. I think the problem is a lot of guys think that 31 inch tires were stock size and they think going up to 33 is not much of a change but the stock size tire for most 4wd half ton trucks measured out to just under 29 inches tall and 9.25 inches wide. Jumping tire sizes up to 33's on 3.08's with an OD gear is a big change in engine RPM and it moves it completely out of the power band for "cruising speed".

 

[Evil Bob]

To be honest 31's are enough to make it bog down at cruising speed to some degree. The 3.08's were garbage for anything with anything more than a 29 inch tire and a 1.1 final drive ratio like the TH350 and TH400 had. It became even worse when they swapped to the 700R4. I think the problem is a lot of guys think that 31 inch tires were stock size and they think going up to 33 is not much of a change but the stock size tire for most 4wd half ton trucks measured out to just under 29 inches tall and 9.25 inches wide. Jumping tire sizes up to 33's on 3.08's with an OD gear is a big change in engine RPM and it moves it completely out of the power band for "cruising speed".

I noticed lol... my 35's are killing my transmission... Hopefully the 4:56's solve all issues.

 

[Rusty Nail]

1988 was supposed to be a good year for a 700r4 too.