Chevy & GMC Vans

First off, well, yes I am....

I am trying to decide what to do with Humpty Dumpty, but I am not sure I understand the gearing ratios well enough to make an informed decision.

What I have is a 97 Conversion with the high top. When I bought it, I thought to myself, all that extra room and nice seats and a TV etc would be the best thing since sliced bread. Now I am thinking that there may be a huge drawback to this.... WEIGHT!

There is a LOT of wood (or woodlike) trim, plus the extra roof. The power rear seat and rear buckets, TV etc etc. There are all kinds of extras on the conversion van.

After driving it for a few months now, I am feeling the big difference between this and my First gen Astro's (91 and 95) which were bone stock.

SO, with all that said, I am thinking about gearing. Basically, I think it is like driving around with 1500lbs of cargo all the time, so I really should look at towing type upgrades. Am I right here or am I over exagerating the feeling and it really is not that much? Am I crazy? ;)

Currently have 3.42 rear.

FIRST real question is what is the biggest difference, in laymans terms to the gearing change? Higher RPM at lower speed? Is it really that simple?

SECOND I have a couple choices. If I go to 3.73 it is easier because I can get a Junkyard axle with similar mileage and just swap the whole thing out. If I go to 4:10 I probably have to re-gear the existing axle. More difficult and probably more expensive. So, is 3.73 enough to feel a difference. I earlier looked at an axle from an 87 with 4.10's but never did it, it was not a direct swap and required some mods, as I recall.

THIRD The previous owner had LOW profile tires on it. 245/60's Did this help or hurt? I thought you could change the tire size to imitate a small gear change, but I have no idea how or what direction.

pics below for reference.


So, help me out with gears.

First of all the 245/60/15 tires were a factory option at one time , so no they didn't hurt your performance at all , if anything i like the way the wider tires make these vans more stable .
as far as gears , with the options you have i'd go with the 3.73 's . unless you do alot of towing then i'd say the 4.10;s would be a better choise .
but either way you go , make sure to recalibrate your speedo . there are threads here about how to do just that thing . good luck & keep us informed about what you did or are doing , with pics of course .

You are sure,you have 3.42's ?
Lots of the conversions had 3.73's .....maybe in part because of any weight difference.

4.10's and 245/60's

Actually it depends on the terrain you drive on mostly. Is it hilly, flat, lots of wind, more city or highway etc? With this info I can make a better decision.

Mostly City, but some highway. I would like to be able to tow my Yamaha Wave Runners (about 2000lbs) for 250 mile drives, which WILL be hilly. Dayton to Central KY, Central KY is hilly.

I checked the RPO codes and I am pretty sure it is the 3.42, I will go look in a few minutes and confirm.

I just bought new tires, so unless the smaller tire size will be a great impact, I dont want to go through that expense.

I also have a 5500 - 6000 lbs camper, which would be nice to tow 1-2 miles at low speeds. I think any gearing will allow me to do that. Just from a storage unit to the campsite, again they are maybe a mile apart if that.

The whole purpose of me buying this was for a trip to Yellowstone next year, which I will tow a utility trailer with tents/gear etc, not TOO heavy, but I will have 5 adults in the van.

Last year we towed our camper with my Expedition and the camper is too much for Yellowstone and the 1500 mile drive, so I want to scale down.

This is probably a 6 month away plan, just trying to get projects lined up.

GU6 is 3.42 correct? If so, that is what I have

Yeah GU6 is 3.42.

First things first...do you have an aux tranny cooler installed? If not, do that now while the trans is still alive. Best mod you can do for these vans.

Now for the gears...For the high top van, hilly, city driving and people hauling and towing you do, go with 4.10's. Your 2WD van is easy as you only need to do the rear axle. I would think it would be between $500 and $750 for a shop to do it. You would then need a programmer to adjust the speedo and shift points.

The guy that did my engine has done swaps before and could re-gear it for $400 labor, if I buy the parts.

Looking at Randys it looks like I need the ring and pinion for about $260 and an install kit for about $100.

Does that sound right?

What kind of interstate RPMs can I expect at 70-75mph with 4.10's?

With stock 215/75's or 245/65's, 4.10 gears at 75 mph you will see right around 2600 rpm's.

With 245/60's, 4.10 gears at 75 mph you will see around 2700 rpm's.

You will find that the van runs awesome on the highway, especially towing or if you are loaded up. If you run empty a lot and you have flat lands to travel on, your mileage will go down some but your city mileage will go up.

The prices sound about right. Labor may be a bit high though. If you like the work he does it isn't too bad.

OK, I found an axle assembly with a 3.73 for $300.00, it isnt 4.10's but its an improvement for very little $$

An axle swap seems pretty straight forward, is it? Just drive shaft and e-brake and shocks?

Yeah it is pretty easy to do. Be sure to change and fill the gear oil!

Before you put down your cash for a used rearend check the gears very carefully. They should have a 1/8" flat area on the top edge of the gear tooth. If it's any thinner, pass on it. These are small rearends for the weight of the van and are a trouble spot.