rear gear change advice

[JOZW30]

OK, so I had my rear differential rebuilt a couple of years ago and I put 3.73 gears in it (it's what the car was born with and I wanted to go back to original), and I really have regretted it as the car now runs hot (doesn't boil over, but consistently runs about 200 degrees). It never ran hot like this before the gear change.

I've played with the timing (even had Eric redo my distributor and carb since the rear change), new radiator, water pump, thermostat, fan clutch is working properly, etc..

I really can't take the car on the freeway any more. Just basically a bad decision I guess.

My question is, I think I've got above average mechanical skills, if I read up, get the right tools, and follow the manual, can I change the gears out myself? everything else should be new. Hate to yank the whole rear and take it to a shop.

Thinking about 3.23's or 3.42's.

Used to be able to hop in the car and just enjoy it, now I look at the temp gauge every two seconds..........

Thanks!

Joe

[PxTx]

I feel if you want to do the job, than you can. Just have to have the right tools and a positive attitude. There is enough technical help on the net. Do you have any of the shims which were removed with the gears you took out?

I don't think your overheating issue is due to the gears. I've posted numberous times that I run 4.88 gears without issue. It is actually more of a street car than a race car. I get 12 mpg on average wiht a 327 and 2 Holley 600's, but have run at 5k R's on the highway for almost an hour straight and no issue.

[Nova Jed]

Just curious, water pump pulley the right dia to crank pulley dia? Water pump going south?

[Alss]

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: pxtx</div><div class="ubbcode-body">

I don't think your overheating issue is due to the gears. I've posted numberous times that I run 4.88 gears without issue. It is actually more of a street car than a race car. I get 12 mpg on average wiht a 327 and 2 Holley 600's, but have run at 5k R's on the highway for almost an hour straight and no issue. </div></div>

I agree..something in the cooling system aint right..wrong pulleys..rotted impeller in the water pump..bad T stat..I would start there.

[JOZW30]

New (last spring) aluminum &quot;performance&quot; water pump.

New modified t-stat (tested before install).

Had 4-core radiator recored and tested.

Lower hose not collapsing.

Same (correct #s) pulleys as on car before rear change.

Moving the initial timing up or down hasn't really made much difference to the thermals. It can sit there at idle after start up and not go above 160-170 degrees all day. Start moving and it slowly creeps up and up and up and will stabilize pretty much just north of 200. Obviously hotter on hotter days.

I thought maybe we didn't get the block cavities cleaned out real good and it's clogged up? has anyone ever tried to pull the lower block plugs while the motor is still in the car? Guessing it's a bloody mess.

One last question about the fan clutch, when the motor is hot, and I shut the car down, should the clutch be tight, or should it spin by hand pretty easily?

Thanks again for responding the 800th &quot;my enigne's running hot post&quot;! [img]<<GRAEMLIN_URL>>/smile.gif[/img]

[RPOLS3]

What about the sender or the guage? NJSteve documented issues with temperature senders with his T/A.

I agree with everyone else that the gear should not be an issue. I run a 3:73 in my Big Block/Auto/A-C Chevelle and last July (80's and humid day) it made the 200 mile round trip to SCR15 with the A/C on full tilt and ran 185-190 degrees on the road and ran up to 200 occasionally at a stop light.

[Plowman]

You don't say what your coolant mix is at,antifreeze protection. I found that any richer than -34 deg is to thick. This will cause the car to run hot down the road and not hot at idle. I would replace the fan clutch too.

[Salvatore]

I agree with everyone else...its NOT the gears.

[olredalert]

----Messy or not I would pull all the lower plugs I could get to. You may have only marginal flow thru the block.......Bill S

[ssl78]

when its at 200 did you ever take a infra red gun and take a reading going into the radiator and out of the radiator to see the temp drop