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Trans van · 12-01-2013, 10:56 AM

Good morning folks
I have a 1983 G30 Chevy Trans Van by champion and had the transmission rebuilt in May. It seems as if it has higher gear ratios then it had prior to. All three gears run about 3 to 400 rpm lower than they used to which is fine for highway cruising but it seems to have trouble pulling itself out of the hole. The transmission rebuilders says that's impossible even though they did change from straight cut gears to helical cut gears for noise purposes. I guess my question is was this transmission specifically built for its nine thousand pound load and is there somewhere for me to find the specs(gear ratios) for it. I'd like to have all my ducks in a row and facts so it is done right the second time :-). It's model number is 83- FM 29356. The transmission has started to fail due to some slippage and stack shifting. They are about to pull it to fix that stuff and I would like them to put the proper gear set in. Great looking forward to being part of this forum.

stink · 12-01-2013, 11:04 AM

The vanes in the torque converter can wear causing higher RPMs at a given speed. The rebuilder is right that different gear ratios are not available for the th400. The rebuilder installed a new or reman converter that is giving you the lower RPMs. Your van does not have the lock-up converter so you will see this at all speeds. If you want to spend the money, you can have a higher stall speed converter installed to give you that little extra "push".

Mekanic · 12-01-2013, 11:41 AM

Lower ratios are Available but they will raise the RPM in the lower 2 gears. Even with the lower gears installed high gear will still be direct drive with no difference in RPM.
TH400 2.75 Low Gear Planetary - TCI® Auto
TH400 (2.75 1ST, 1.57 2ND) LOW GEAR PLANETARY Retails $768.75
I'm sure that this gear set would be cheaper though their authorized sales outlets.
If you would happen to be doing a rebuild these gears wouldn't take a extra min to install. But a trans has to come Completely apart to install these gears.

Stink is probably right on you RPM difference now . 99% chance the torque converter is just a bit "tighter" A hgiher stall speed will result in higher trans fluid temps and worse MPG. Something i suspece you 83 GM van needs no part of.

OrngTrillium · 12-01-2013, 12:12 PM

Welcome to the forum, good luck with your issue. I'm not quite that mechanical yet so I can offer you no help. Or I could try to help you and make things worst. Good luck keepin' that classic on the road. We all need to see those units on the road, point to it and tell our kids that's what it looked like when I was in diapers!

Medico · 12-01-2013, 12:53 PM

Welcome and glad to meet you!

Perhaps moving this to a more appropriate forum would get more possible answers.

MSHappyCampers · 12-01-2013, 01:33 PM

Welcome to IRV2! We're sure glad you joined the gang here!

Sorry about your tranny troubles!

Hope you get it figured out!

Good luck, happy trails, and God bless!

Trans van · 12-01-2013, 06:15 PM

Thanks everyone
Excellent info, having a strong transmission is what I'm after. Assuming the gear ratios are the same in all factory stock TH 400's no matter the application than all is good and ill keep my trap shut. I do get much better MPG's post the first rebuild. I plan to keep this for a very long time so some day I just might lower the gears in the rear end and add a pricey gear vender overdrive unit. Getting to the camp location is half the fun

Again thanks for all the info.