Bought Suburban With A Non-factory Differential In It

[Jerry Davis]

Guys, I am new to this forum and appreciate all comments. I bought a used '95 Suburban a few months ago and really like the beast. It is old though and I am considering selling it for a fresher horse. I bought it used from a guy several months ago, and noticed that when the speedometer reads 55, I am actually going 65MPH. At an indicated 60MPH, I am actually going about 75MPH. The former owner told me that he swapped out the diff in order to get better highway fuel mileage. (that didn't happen

 

But I bought a small trailer (2000 pounds on the trailers axle) and this sucker barely pulls it up anything more than a 3-degree incline. I cannot even attain an actual 60-mph with the gas pedal on the floor

 

I suspect the energy problem is the taller gearing in the rear end. To repair the diff, how do I ID the correct differential? Will simply swapping out the entire real axle from a salvaged unit be more cost effective? Is it possible that this tall gearing is not the problem?

 

 

Thanks for reading.

 

Jerry Davis

Houston, TX

[dewfpo]

You can check the gearing you currently have by marking your tire and your drive shaft with chalk and have someone slowly move it exactly one tire rotation as you count the number of drive shaft revolutions. That will give you your rear axle ratio. I don't know if the RPO codes are in your glove box but you might check. If they are you can decipher what your truck came with.

 

DEWFPO

[truckofwinandawesome]

also, you can go to http://www.compnine.com/vid.php enter your VIN, and it will show you what is SUPPOSED to be inside that Rear End.

[wavery]

Guys, I am new to this forum and appreciate all comments. I bought a used '95 Suburban a few months ago and really like the beast. It is old though and I am considering selling it for a fresher horse. I bought it used from a guy several months ago, and noticed that when the speedometer reads 55, I am actually going 65MPH. At an indicated 60MPH, I am actually going about 75MPH. The former owner told me that he swapped out the diff in order to get better highway fuel mileage. (that didn't happen

 

But I bought a small trailer (2000 pounds on the trailers axle) and this sucker barely pulls it up anything more than a 3-degree incline. I cannot even attain an actual 60-mph with the gas pedal on the floor

 

I suspect the energy problem is the taller gearing in the rear end. To repair the diff, how do I ID the correct differential? Will simply swapping out the entire real axle from a salvaged unit be more cost effective? Is it possible that this tall gearing is not the problem?

 

 

Thanks for reading.

 

Jerry Davis

Houston, TX

I doubt if gearing is your problem. I have 3.23 gears in my '06 with 4.8L V8 and I can pull a 6% grade (in 2nd gear) @ 65MPH towing our 4,000# pop-up trailer with no problem. I have to drop to 2nd @ 3600RPM but that's not an issue,

 

I would suspect that you have a mechanical problem like a bad cat converter or 02 sensor (or both).

 

The RPO codes won't help if the rear end has been changed. Counting the tire revs & deviding by the D/S revs will give you your correct ratio. Also, check the tire size against the door jamb sticker.

[brainpause]

Guys, I am new to this forum and appreciate all comments. I bought a used '95 Suburban a few months ago and really like the beast. It is old though and I am considering selling it for a fresher horse. I bought it used from a guy several months ago, and noticed that when the speedometer reads 55, I am actually going 65MPH. At an indicated 60MPH, I am actually going about 75MPH. The former owner told me that he swapped out the diff in order to get better highway fuel mileage. (that didn't happen

 

But I bought a small trailer (2000 pounds on the trailers axle) and this sucker barely pulls it up anything more than a 3-degree incline. I cannot even attain an actual 60-mph with the gas pedal on the floor

 

I suspect the energy problem is the taller gearing in the rear end. To repair the diff, how do I ID the correct differential? Will simply swapping out the entire real axle from a salvaged unit be more cost effective? Is it possible that this tall gearing is not the problem?

 

 

Thanks for reading.

 

Jerry Davis

Houston, TX

I doubt if gearing is your problem. I have 3.23 gears in my '06 with 4.8L V8 and I can pull a 6% grade (in 2nd gear) @ 65MPH towing our 4,000# pop-up trailer with no problem. I have to drop to 2nd @ 3600RPM but that's not an issue,

 

I would suspect that you have a mechanical problem like a bad cat converter or 02 sensor (or both).

 

The RPO codes won't help if the rear end has been changed. Counting the tire revs & deviding by the D/S revs will give you your correct ratio. Also, check the tire size against the door jamb sticker.

 

 

+1 to all he said.

 

I once worked for a fire department that had one of about that same vintage. it was a dog, but it might still have pulled in 2000 pound trailer.

 

 

Larry