tow vehicle question

[Rick Alston]

LauraandWayne

I own an '89 GMC 1500 with 350 TBI and the 3.41 rear-end. Around town I get 13.5 mpg and about 10 while towing 31' AS.

I found a satisfactory solution: K&N air filter and synthetic motor oil and transmission fluid. Mountain climbing in western Virginia became much easier with the K&N filter. Note-K&N uses a red colored oil to treat the filter after its periodic cleaning!

I use synthetics because they are better in the cold and hot temperatures than are the standard oils. I am a performance nut, not one to use synthetics to extend the oil change intervals beyond 3,000 miles. Yes, I pay more for the synthetic oils, but I think the payback is better performance and longer engine life.

My engine temperature gauge stays at 190 on level ground at 60 mph and climbs to 205 on hills. Slight grades seem to make no difference in engine temperatures.

Rick

[wayne.yl]

59Toaster
I'm trying to get in touch w/ p/o but until now no word about the speciific rearend. Hope this isn't a bad sign. Anyway, is there another route to determining the type axle and gears on the burb?
Wayne

[Ernie2007]

I tow my '86 34 ft limited (7400lbs) with a Chev 1500 with the off road and towing package; it has a 5.3 L engine and auto trans. and the lower geared rear end. I get about 14 mpg under most conditions and 17-19 when not pulling the trailer. I do use a load leveling system and generally carry 250 to 500lbs in the bed of the truck. I have no trouble towing this up mountain roads. I do have the transmission, transfer case, and deferentials serviced each year ($300 is cheaper than buying a bigger truck). You could get better mileage with a Chev 2500 with the Duramax and the Allison trans. You would generally get about 17 mpg even up hill. But the price of the truck is about 10 grand more. The suggestion about the K & N air filter is a good one you'll get more hp. The tuning chips for this truck do very little good, but are great for the Duramax.

Have fun with trailer. Best Ernie

[davidz71]

Here is an easy way to determine axle ratio. Take some chalk or a piece of masking tape and mark a spot on the tire (let's say near the outside edge at say 9 o'clock). Now, mark a spot on the driveshaft you can see when you position yourself in front by the tire. Put the axle on jackstands (may work with this one tire off the ground) so that both tires are off the ground. Slowly turn the tire forward as if it was in gear and see how many times the driveshaft mark goes around for a complete revolution of the tire. If the shaft goes around not quite 3 1/2 times then you have a 3.42 ratio, almost 3 3/4 times then you have a 3.73 and if it goes around a little more than 4 times then you probably have a 4.10 ratio.

[59toaster]

Originally Posted by laurandwayne

59Toaster
I'm trying to get in touch w/ p/o but until now no word about the speciific rearend. Hope this isn't a bad sign. Anyway, is there another route to determining the type axle and gears on the burb?
Wayne

If they put anything other then the 10 bolt in there it was an upgrade.
Count the bolts holding the cover on. 10 it's a 10 bolt. 12 it's a 12bolt, 14 it's a 14 bolt.
Now how many lug bolts? if it has 6 lugs but 14 on the cover that's the 3/4 ton Semi floating 14 bolt. It's a good axle and much better for towing then a 10 bolt buecause it has a larger ring and pinion.

http://www.coloradok5.com/axleguide.shtml
That has some ID info on the axles.
On the gear ratio.

Well I always pup covers on new to me vehicles to inpect stuff. I'd count teeth or on the edge of the ring gear will be some numbers. The center set of numbers will be something like 9:37 That's the number of teeth on the gears. Divide the larger number by the smaller and that's the gear. So 37 / 9 =4.11. The higher the number, the lower the gear, the easier it is for the engine to move the weight. So in third gear or D on your truck the engine would have to spin 4.11 times for every single revolution of the tire.

If your leary about pulling the cover the easiest thing to do is put a chalk mark on the tire at 6 o-clock. Put a chalk mark on the drive shaft at 3 o-clock and make a reference mark on the axle housing. Have somebody slowly drive the truck forward till the tire makes one full revolution. Count how many times the drive shaft spins. On a 31 inch tire your going to need a place where you have 63.14 inches to move the truck.
GM axle ratios are:
2.73 Gas crunch gear in the 80's
3.08 common on 10 and 12 Default V8 gear most of 70's and a lot in 80's
3.42 common on 10 Suburbans and K5 with base tow package and or 4x4
3.73 common on 10 with HD tow package, 12 with HD tow package, 14 SF and 14 FF 3/4 ton aps.
4.10 common on 12 older 6 cly trucks and some HD tow package manual transmission trucks, 14 sf and FF on 3/4 and 1 ton
4.56 Common on 14FF 1 ton

[wayne.yl]

John-boy
Thanks to forum member, Rick Alston and the speedy oiler guy, I found out what the red oily stuff is in the Air filter pan. Its the oil the K&N air filters are treated with after they are cleaned. Learn something new all the time. I now remember the P/O saying something about using that type air filter. Now I have turned my attention to solving the mystery about the truck's rearend. Thanks everyone for the helpful advice about this mystery. Hopefully I will know soon. This forum is so awesome!!
Wayne

[krowsea]

Originally Posted by laurandwayne

John-boy
Thanks to forum member, Rick Alston and the speedy oiler guy, I found out what the red oily stuff is in the Air filter pan. Its the oil the K&N air filters are treated with after they are cleaned.

Well, that turned out better than I feared. The K&N is a great filter. There's a cleaning/re-oiling kit available (part# 99-5000) when you get around to servicing it. If there was filter oil in the air filter housing, the PO put too much oil on. Once it's cleaned, you only want to put enough oil back on to return the filter to it's original pink color. The oil comes in an easy to use aerosal can.

John-Boy

[krowsea]

Originally Posted by 59toaster

If your leary about pulling the cover the easiest thing to do is put a chalk mark on the tire at 6 o-clock. Put a chalk mark on the drive shaft at 3 o-clock and make a reference mark on the axle housing. Have somebody slowly drive the truck forward till the tire makes one full revolution. Count how many times the drive shaft spins. On a 31 inch tire your going to need a place where you have 63.14 inches to move the truck.

Great suggestion Toaster-Guy. A 'slightly' easier method, using the same technique you suggest, is to jack the rear of the truck up and support it off the ground on jack stands. Make the same mark on the inside bottom sidewall of the tire and another mark on the bottom of the driveshaft near the differential. Now, with the trans in neutral, spin the tire one revolution and as you mentioned, count the driveshaft revolutions. Just another idea.

John-Boy

[87MH]

Originally Posted by laurandwayne

......I found a '90 suburban 350ci w/ tbi and a 1ton rearend kit added by the previous owner. ......

Crawl under the burb, there should be a tag secured by one of the differential cover bolts that looks like this (Picture 1).

41 teeth on the main ring, 9 on the pinion.

41/9 = 4.555556 (4.56)

The second pic is of the one ton Dana 10 bolt dually (4.56) axle under the '87 345 Motor Home.

[59toaster]

Originally Posted by krowsea

Great suggestion Toaster-Guy. A 'slightly' easier method, using the same technique you suggest, is to jack the rear of the truck up and support it off the ground on jack stands. Make the same mark on the inside bottom sidewall of the tire and another mark on the bottom of the driveshaft near the differential. Now, with the trans in neutral, spin the tire one revolution and as you mentioned, count the driveshaft revolutions. Just another idea.

John-Boy

The differential will make your reading wrong if you only spin one tire at a time. Have to spin them both in unison to keep the diferential out of the mix. If it has a limited slip then your way will work perfect. If it's a open diferential you will have to have somebody else spin the oposite tire the same direction.

[andoboba]

Originally Posted by 59toaster

If they put anything other then the 10 bolt in there it was an upgrade.
Count the bolts holding the cover on. 10 it's a 10 bolt. 12 it's a 12bolt, 14 it's a 14 bolt.
Now how many lug bolts? if it has 6 lugs but 14 on the cover that's the 3/4 ton Semi floating 14 bolt. It's a good axle and much better for towing then a 10 bolt buecause it has a larger ring and pinion.

Ok, now I feel I must chime in as this so called Dana 10 bolt is not what you think it is. GM made most of their diffs for themselves and called the Corporates. Corporate 10 bolt, Corporate 12 bolt and of course the imfamous Corporate 14 bolt. The 10 bolt being the weakest due to smaller size and axle bearing configuration was used mostly years ago on muscle cars and half ton trucks. Currently GM is still puting Corp Diffs under their half ton trucks, they are just using the Corporate 12 bolt. The heavy trucks and Suburbans of today, mostly 3/4 ton got outfitted with the Corporate 14 bolt. This unit has a full floating axle bearing assembly and is one of the stoutest diffs in this level of service. For one ton trucks GM used Dana 60's and 70's. Now it is these units that I think you folks are confusing for the very light duty Corp 10 bolt. Yes they do have 10 bolts on the cover but they are made by Dana and thus are a Dana 60's or a Dana 70's. You can identify this by looking for a casting number "60" on the lower portion of the housing just to the right of the pumpkin. These are extremely stout units which have twice the load rating of the old 10 bolt. Some people also confuse a Dana 44 which is very common in many trucks, for a Corp 10 bolt due to the fact that all three of these Dana units have 10 bolts in their covers. So be happy, my guess is that you have a Dana 60 or 70 which are GREAT units!!! GOOD LUCK

[Silvertwinkie]

I have an '04 3/4 ton Suburban and it does not have the 14 bolt full floating axle. It is a 14 bolt semi-float. This is the standard 3/4 ton differential with the only option/upgrade that it is a locking differential.

It appears to me that the full floating axle is not avail on at least the 2004 Suburbans from what I can tell for sure. It seems to me that the full floaters are on the Silverado line and HD trucks and commercial trucks.

[87MH]

On the Dana 1 ton Axle pictured in my post above -

What is the proper level of the differential fluid?

1/2" below the filler plug?

To the bottom of the filler plug?

Just to spill-over (low point) of the axle tube?

Need help - don't want to put too much in (foaming problems?), but don't want to put in too little. I lost about a pint when I pulled the curb side axle and rotor assembly.

[andoboba]

Originally Posted by Silvertwinkie

I have an '04 3/4 ton Suburban and it does not have the 14 bolt full floating axle. It is a 14 bolt semi-float. This is the standard 3/4 ton differential with the only option/upgrade that it is a locking differential.

It appears to me that the full floating axle is not avail on at least the 2004 Suburbans from what I can tell for sure. It seems to me that the full floaters are on the Silverado line and HD trucks and commercial trucks.

Yes, that is true. You have the 9.5 inch ring gear semi float 14 bolt which is an offshoot of the Corporate 12 bolt which has the 8.5" ring. I do as you say have a Silverodo '94 3/4 ton which does have the full float. You can tell by the housing size and the axle tubes have the bolts holding in the "pull out" axle. If you have a choice the later, it is much more stout. Less ground clearance but it has a 10.5" ring gear.
After '96 GM made a lot of changes. Much fancier units with much higher cost. I have a feeling your 9.5 semi float 14 bolt is plenty stout for anything other than maybe yarding logs

[andoboba]

Originally Posted by 87MH

On the Dana 1 ton Axle pictured in my post above -

What is the proper level of the differential fluid?

1/2" below the filler plug?

To the bottom of the filler plug?

Just to spill-over (low point) of the axle tube?

Need help - don't want to put too much in (foaming problems?), but don't want to put in too little. I lost about a pint when I pulled the curb side axle and rotor assembly.

First I want to say that the type of lube makes a big difference. Synthetic Oil will lube everything much better. Foaming, thermal breakdown and molecular shearing just are not issues with a product like Red Line Synthetic Gear Lube with the friction modifiers!! It is expensive but worth it!
If you have a differential housing that has not had the oil changed for long time it will be too dirty to just "add some oil". Just breakdown and do a full change. If it has been say 100K miles since the last time I would even do a change with normal cheapo gear lube, run it for a couple thousand miles to flush contaminate drain again and then add the Red Line. Once you put the synthetic in the housing you are good for a long long time!
Sorry, to answer the question just fill the housing untill oil starts to seep out of the fill hole. Make sure you are on level ground or you could under/over fill. A little too much oil and it will just come out the breather tube, no big deal just messy

[59toaster]

Originally Posted by andoboba

Ok, now I feel I must chime in as this so called Dana 10 bolt is not what you think it is. GM made most of their diffs for themselves and called the Corporates. Corporate 10 bolt, Corporate 12 bolt and of course the imfamous Corporate 14 bolt. The 10 bolt being the weakest due to smaller size and axle bearing configuration was used mostly years ago on muscle cars and half ton trucks. Currently GM is still puting Corp Diffs under their half ton trucks, they are just using the Corporate 12 bolt. The heavy trucks and Suburbans of today, mostly 3/4 ton got outfitted with the Corporate 14 bolt. This unit has a full floating axle bearing assembly and is one of the stoutest diffs in this level of service. For one ton trucks GM used Dana 60's and 70's. Now it is these units that I think you folks are confusing for the very light duty Corp 10 bolt. Yes they do have 10 bolts on the cover but they are made by Dana and thus are a Dana 60's or a Dana 70's. You can identify this by looking for a casting number "60" on the lower portion of the housing just to the right of the pumpkin. These are extremely stout units which have twice the load rating of the old 10 bolt. Some people also confuse a Dana 44 which is very common in many trucks, for a Corp 10 bolt due to the fact that all three of these Dana units have 10 bolts in their covers. So be happy, my guess is that you have a Dana 60 or 70 which are GREAT units!!! GOOD LUCK

A. I didn't say anything about a "Dana 10 bolt". That was 87MH the axle pictured is a Heavy truck axle used in the P30 chassis. It does indeed have 10 bolts but you are correct in that it is probably a Dana 70 as the more correct and recognized name but there are some that refer to the bolt count. Because the other axle available under Motor homes is the Sterling and it has a different amount of bolts.

Please do not quote me and then say something posted by somebody else is wrong and mislead folks to think I said it.

I moderate one of the highest traffic GM truck sites on the net. www.coloradok5.com it’s 2.5 million hits a month on average. I am also a respected member of www.67-72chevytrucks.com GM trucks and modifying them is my hobby.

I am particularly knowledgeable about the 67-91 Year ranges. I have owned 1970 Suburban, 1975 Jimmy, 1979 Blazer, and 1988 R20 Suburban in the last 5 years. I have a pretty good handle on them and what was available in them and when they had changes both cosmetic and mechainical

I have no problem admitting when I am wrong but I do have a big problem with somebody making a post that appears to give me a tongue lashing me especially when you have wrong info and you’re lashing me for something I didn't say.

B.

they are just using the Corporate 12 bolt. The heavy trucks and Suburbans of today

GM has not made a 12 bolt in 23 years. GM made the last 12 bolt in 1981. They have not made one since. 81 was the transition year where the complete drive train was redone as well as a cosmetic up date. First year for the 10 bolt truck rear, first year for the 700R4, first year for the NP 208 transfer cases. 81 still had some 12 bolts being installed as the axle plants retooled. You got either a 10 bolt or a 14 bolt after 81 for rear axle and a Corp 10 front or D60 front on the 4x4. Some trucks got the Dana 70 rear including the P30 chassis of the vast majority of Motor homes made then.

End of discussion.

C. The picture is not the axle in question.

D.

, mostly 3/4 ton got outfitted with the Corporate 14 bolt. This unit has a full floating axle bearing assembly and is one of the stoutest diffs in this level of service.

In the 70's it is true that 3/4 tons got the full floating 10.5 inch ring gear variation.

In the mid to late 80's when the 14 bolt corporate Semi Floater (C-clip axle like a 10 bolt but a 9.5 inch ring gear) was introduced. It was introduced because GM realized they just shot themselves in the foot with the loss of the 12 bolt. The 14SF is actually stronger then the 12 bolt and rounded out their offering because it could be made with 6 lugs for HD 1500 towing packages. So "through current" is not a true statement. Most light duty 3/4 tons (anything with a 350cid or smaller) after that time frame were equipped with the SEMI floating 14 with the 9.5 inch ring gear. The Full floating only made it behind 454 powered 3/4 ton trucks (concidered the HD) from Mid 80s to current. I own one such truck. I had to search for it.

Just for reference: GM Never made a 1 ton Suburban and suburban 4x4. 2 things make a 1 ton and one is the frame height (to make it stronger) and the second is the front axle. Because of the floor height of the cargo floor GM was restricted on how tall the frame was to give the clearance needed over the axle. Unlike the trucks where there was both metal thickness differences as well as frame height it was not possible on the Suburban to make the frame taller. Just as a little twist to really confuse people they then put a 8600lb GVWR on the 454 Burb. That was to beat emisissions requirements.

The D60 front axle was never available under the Suburban 4x4 even to the Army. So knowing this we also know that a 454 was also never available in a 4x4 Suburban built between 1967 and 1991. GM would not put the 454 in front of the D44 or Corp 10 front axle OR the 14sf rear. GM knew the engine could produce more torque then those axles coule reliably handle. The 454 was available to make the truck a family friendly prime mover for people towing campers.

For fun I like asking people to prove they have a 1 ton Suburban but taking a picture of the RPO sticker in the glovebox. I been at it for 4 years and so far nobody has risen to the challenge and proved me wrong. I have a lot of pictures of 8 lug 10 bolt axles sent to me though.
Those dually burbs that pop up are an aftermarket conversion to a 3/4 ton. I have personally looked at the RPO stickers on 2. They list the truck leaving the plant as such.

The Semi floating 14 with the 9.5 ring gear is available in both 6 and 8 lug variations. GM also did some stupidness by rating Vans as 2500 with a 10 bolt axles. My old Company Van was a 95 Vandura 2500 with a 10 bolt. I broke that axle by 40k on the odometer. Bearing failure as you noted. The 6 lug 14 was used in a lot of 85 up Suburban 1500's with the HD tow package. It is also used in a lot of 88-current trucks with the HD tow package 4x4's like the Z71's.

Also another point of random information if you happen to be axle hunting: Vans run axles 3 inches wider then the rest of the truck line Through 95. The only other truck GM had that did that was some of the pre 71 Suburban Carryalls. It will require welding new spring purches to mount on anything else GM offers. That same time frame the 4x4 trucks tracked 3 inches wider front then rear. The 88 up tracks same front and rear. The new truck is also not as wide as the previous body and uses the same width rear axle as the previous body with a more offset rim to account for the IFS front suspension needs to hold correct steering geometry.

F. GM farms out plenty of their axle manufacturing to DANA. The 10 bolt front axle was built by DANA Corporation. Everything from the knuckle out is interchangeable between D44 and Corp 10 bolt. It you want to you can put a D44 Ford knuckle assembly and stub shaft on a Chevy 10 corp and bolt throw it right under a 70's-mid 80's Dodge 4x4 truck if you like. With the exception of the drag link it would be a bolt on. The Ford uses a Cross over steering to the passenger side and GM and Dodge use a short drag link to the driverside knuckle. GM 10 bolt is a direct bolt in to a Dodge except that Dodge uses 5 lugs.

If you look on the Diff housing you will find a lot of GM axles with the Dana Diamond "<>" cast into them when they manufactured the axle under contract from GM. I know my 79 K5 had it. My 75 Jimmy has had the D44 swapped out for a Corp 10 but I will have to look to see if it was a Dana assembled unit.

G. GM did not use the D44 rear variation to the best of my knowledge in these year ranges (67-current). Before the "Corp" axles they were Using Eaton, NEAPCO axles or the D60 for the rear. The Eaton’s and Neapcos were third member drop out style like a Ford 9 inch. I think 67 was the first year the D44 front was used with the 260 series u-joint. The axle was revised by 74 to use a larger 297 u-joint.

Now this is all off the top of my head so might be a couple discrepancies.

[59toaster]

Originally Posted by andoboba

Yes, that is true. You have the 9.5 inch ring gear semi float 14 bolt which is an offshoot of the Corporate 12 bolt which has the 8.5" ring. I do as you say have a Silverodo '94 3/4 ton which does have the full float. You can tell by the housing size and the axle tubes have the bolts holding in the "pull out" axle. If you have a choice the later, it is much more stout. Less ground clearance but it has a 10.5" ring gear.
After '96 GM made a lot of changes. Much fancier units with much higher cost. I have a feeling your 9.5 semi float 14 bolt is plenty stout for anything other than maybe yarding logs

8.5 is the 10 bolt. 12 was 8 7/8 I believe. I can get a measurment if you like. I have a 12 bolt R&P I am about to put on E-bay. The Ford 9 inch was a typical Ford 1 ups deal like the 351 winsor motor, the 460 etc.

Also there is a ligher duty 10 bolt for the S trucks I think it's a 8 inch.

[andoboba]

Originally Posted by 59toaster

8.5 is the 10 bolt. 12 was 8 7/8 I believe. I can get a measurment if you like. I have a 12 bolt R&P I am about to put on E-bay. The Ford 9 inch was a typical Ford 1 ups deal like the 351 winsor motor, the 460 etc.

Also there is a ligher duty 10 bolt for the S trucks I think it's a 8 inch.

I just want people to know that 10 bolts on the cover could be one of many differentials. Sorry about the confusion, I just don't often hear people calling a Dana 70 a 10 bolt.
What is a R20 Suburban? I know GM call the Suburban a G model and C classifies two wheel drive and K classifies four wheel drive. I can not figure out what the R means?

[87MH]

[QUOTE=andoboba]... Sorry about the confusion, I just don't often hear people calling a Dana 70 a 10 bolt.[QUOTE]


Sorry, guys - my fault -

I meant to say 10 lug - (Number of "bolts" (lugs) on the rim.)

Mea Culpa.

[59toaster]

Originally Posted by andoboba

I just want people to know that 10 bolts on the cover could be one of many differentials. Sorry about the confusion, I just don't often hear people calling a Dana 70 a 10 bolt.
What is a R20 Suburban? I know GM call the Suburban a G model and C classifies two wheel drive and K classifies four wheel drive. I can not figure out what the R means?

In 1988 GM had a body revision on the trucks.

The "round" body came out. GM had a contract to supply the Military with trucks for 10 years. They had to keep plants making the old body truck till they were sure they could fullfill the contract they signed in 82. So now GM was making two completly different full size trucks.

To diferentiate (sp) the old from the new the Round trucks kept the C 2wd and K 4wd designations. The Square body trucks became "R" 2wd and "V" 4wd. In 89 GM did a grill change to make the Square trucks sort of look like the round trucks from the front. They updated the interrior as well.
So on the Crew cabs, Suburbans, and Full size Blazer and Jimmy they were still the 73 body change plus cosmetic updates.

Now here is a Twist. While if you as a civilian ordered a 1988 K30 single cab or extended you got the new body. The Army was still geting single cab Square body trucks till 92.

These are hitting the market now for Gov auctions and cause a lot of confusion. Some folks didn't know they existed and those years are a BIG gray area to a lot of aftermarket people. You will find a lot of stuff not listing stuff for GM Subs and K5's for 88-91. You have to order the 87 parts to make sure you get the right ones and even that is a crap shoot. In 91 The 4L80 was installed in the trucks to replace the TH400. In 89 there were major revisons on the accessory drives including a reverseflow water pump on the surpentine. In 90 there was a new vairent of the 454 and it runs a unique FI to fit the old body to the new engine.

If you own a 88-91 R or V you better know what is what or your going to get handed a lot of wrong parts at Auto Zone or any of the chain places. \


Ohh I was wrong on something. The S truck 10 bolt is a 7.5.