I've an '88 xlt lariat, straight 6, 2.73 diff. the basic city truck. With 358,000+ km its time for a rebuild. I need to pull 3000 lbs of trailer(7x14 tandem). How much torque will i gain regearing to 3.08 or 3.55. just have 3sp auto so i don't need it wailing like a banshee on the highway.

Also, is there a cam that will ice the cake yet get me through emissons testing(mandatory yearly to get insurance).

 

Well you won't gain any torque by changing your rear diff. It wil allow you to pull your trailer easier. Of course you will lose top end because of the taller gears. 3.55 would be plenty for a 3000lb trailer.

 

highmark,

CHech out the following site. http://www.wallaceracing.com/reargear.htm It has a chart that will show the increase decrease of torque achieved by changind the rear gear ratio. 3.55:1 would be 30% increase.

For camshafts try crane

http://www.shopcranecams.com/for6cyl19192.html


Regards

Jean Marc Chartier

 

You sorta got it right, but not completely. You are correct that changing gears will not change the performance of the engine. However, more torque will be availble at the rear wheels, which is the real world. So I would say, YES, changing the gears will give you more torque for towing.

Remember from physics, torque = distance X force. (the unit of measure on a torque wrench is foot-pounds)

Lower gears act just like a longer handle on your wrench - that means more torque to tire.

Hope this helps!

 

By regearing, you're not "gaining" any more torque...it's measurement is independent of transmissions, gearing, etc. What you are doing is changing where your engine operates (RPM's) thus possibly better utilizing the torque band.

 

I guess I should have been more clear. I was just pointing out that changing gears wouldn't cause his engine to produce more torque.

Actually I try to forget.

 

If i switch from 2.73 to 3.55, what can i expect in rpm increase a 60 mph when i only have a 3 spd auto?

 

To find your new rpm, use this formula, "current rpm @ 60 mph x (3.55/2.73)", or multiply your current rpm at 60 mph by 1.30037. I changed from 3.08 to 3.55 in my truck and improvement was very noticeable. If you go from 2.73 to 3.55 gears, you will think someone has slammed into you from behind the first time you take off from a stop. I tow in 4th at 60 mph and see 2750 rpm. If you have a 3 speed auto, you will see approximately the same rpm at 60 mph in 3rd. Hope this helps. GlennMc.

P.S. If you do the change yourself, use Ford Motorsport gears. They are designed to the "Master housing dimension" or standard pinion depth that Ford uses for their gears and it will simplify installation. Mine went in perfectly without changing from factory shim settings on the pinion. Aftermarket gears don't use the same system and you will likely do more adjusting to get things right.

 

You are only partially right. Gears do change the RPM at crusing speed, which may put the engine in a meater part of the power band (or may cause you to over-rev the engine). But gearing will also change the rear wheel torque.

There is flywheel torque and there is rear wheel torque. Gears do not affect flywheel torque, but when towing, you are most interested in rear wheel torque - that's what you feel in the seat of your pants. The lower the gears, the more torque.


Gears are like levers:

-----------
___^___
Push down 5lbs on on side and you can lift 5lbs on the other


----------
____^__
Move the lever so that one side is twice as long as the other.
Push down 5lbs on the left side and you can lift 10lbs on the right.

In the same way, gears multiply force.

 

highmark,

The Torque at the rear wheels is what counts. If you want more, change the gears. Plain and simple.

JMC

 

Does anyone know where i can dollar compare diff gears in canada?

 

highmark,

It has been my experience that auto parts are less expensive in the States. The aftermarket parts you will purchase in Canada most likely originated there. Mail order is most likely the best bet on this one.

JMC

 

Just about any online shop sells ring gear and pinion sets. You have an 8.8 Rear End which is the same (minus limited slip) as the Mustangs.

A good place in Canada where's I've ordered things for my mustangs has been Western Motorsports

I would recommend going with Ford Racing Performance Parts Gears and they can be found at just about any Ford Dealer, One of the best priced Ford Dealer around is here in Georgia Gene Evans Ford

If price is your main concern probably the cheapest gears out there is sold at National Drivetrain

I hope this helps.

I too plan on changing my 3.55's out for some 4.10's very soon but not for pulling a trailer but for the haul butt purpose!

-Adam

 

highmark;

Whereabouts are you in Canada? I bought my Ford Motorsport gears from Bolt-on Performance in Bolton Ontario and paid less that $400 Canadian for them. If you have questions about this upgrade, I may be able to help. I have done it already. Post back if you are in the area. GlennMc.

 

Hey highmark:
I have some ford 327 gears out of my 2002 mustang. they are just sitting here in the closet. if you want them i would sell them for $65 plus shipping. have about 19,000 miles on them.